Description and History of the Sport

The cutting horse was born of necessity long ago on the open grass plains of West Texas. This was the era of Western history that included big cattle drives from the open ranges of ranches such as Burnett and the 6666 Ranch, Waggoner Ranch, the Pitchfork Ranch, and the Matador Ranch to Dodge City, Kansas. Cutting horses enabled big country ranches, where no barbed-wire fences existed, the only means of working vast herds of cattle. In those days the task of the horse was simple, at least by definition. Guided by the rider, the cutting horse entered a herd of cattle quietly and deliberately. A single cow was cut, or separated, from the herd. The natural instinct of the cow is to return to the safety of the rest of the herd. The cutting horse, through breeding and training, controlled the cow with a series of moves and countermoves. The speed, agility, balance, and quickness of the cutting horse kept the cow from the herd, where other cowboys would hold the cut. The horse and rider would reenter the herd again and again, cutting cattle out until the work was done. Only the top hands earned the right to ride the best horses of the remuda (herd), the cutting horses.

The unique skills of the cutting horse were a great source of pride to the frontier cowboy. This often led to impromptu or jackpot cuttings on the open range or, from about 1900, in outdoor pens of the large ranches. From this love of the cutting horse, as well as the subsequent competition to determine who had the best horse, came the roots of cutting as we know it today. The first cutting horse contest for money was held at the 1898 Cowboy Reunion in Haskell, Texas. Twelve cutting horses competed for a purse of $150. From this start, regular events occurred on ranches of the Southwest and at the Fort Worth Stockyards. Rules and prizes varied greatly, but the ability of the cutting horse to separate a single cow from the herd always was and continues to be the goal of the competition. From these roots the National Cutting Horse Association was formed in 1946 during the Fort Worth Exposition and Fat Stock Show. The stated purpose of the organization was to standardize the rules and judging of competition and to preserve the tradition and history of the cutting horse with the ranching and livestock industry.

Today competitions approved by the National Cutting Horse Association occur throughout the United States and Canada. In addition, many association members from other countries, such as Australia, are conducting competitions outside North America. The format of these competitions and other Western performance horse disciplines, such as reining, presents a unique challenge to the equine veterinarian.

Training

Training of the cutting horse begins at 2 years of age. Usually 60 to 90 days are spent in basic training before the horse is introduced to cattle. This generally is accomplished by turning one cow into a round pen that is 38 to 54 m in diameter. The horse is taught to mirror the movements of the cow as the cow moves around the perimeter of the arena. This process of training a cutting horse is repetitive and is done several days a week for months. The object of training is for the horse to develop an ability to perform identical movements with the cow. Simply put, when the cow stops or stops and turns, the horse does the same maneuver. This type of training is accomplished by asking the horse to stop with the aid of a bridle and turning the horse to move with the cow. The key to training is a complete and balanced stop. With time, a stop ultimately is followed by the instinctive ability of the horse to “read” the movement of the cow and to turn in the direction the cow is going. Because this ability to watch a cow and respond to its movement is instinctive to the working stock horse, breeding is of the utmost importance. Without this genetic instinct a horse simply does not respond to the movement of a cow and does not initiate a stop or turn as necessary to continue to track the cow. A good cutting horse trainer knows in a relatively short period if a young horse has the instinct and athletic ability to be a successful cutting horse. A finished cutting horse must perform the necessary moves to keep a cow in proper position away from the herd, without any hand cues from the rider, relying on instinct alone to read the movement of the cow. Reining the horse is permitted only to make the cut of a single cow out of the herd. After the cut is successfully made, the reins are placed in a relaxed position on the horse’s neck, and only leg cues are permitted from the rider during the actual working time. The ability of a horse to contain an individual cow provides the excitement of competition in cutting.

Training of a cutting horse prospect that has shown good potential continues when it is a 3-year-old, preparing it for the first major competitions, the futurities. The futurity is the first of the horse’s aged event competitions that continue for 4 years. No horse can compete in aged events beyond 6 years of age. Aged events consist of two elimination go-rounds, followed by the semifinal and the final competition. Substantial musculoskeletal stress is placed on these athletic performance horses, with multiday competitions over a short period. In addition, the horses usually are practiced with cattle daily, including the day of competition, to sharpen performance skills. Competition in these aged events is heavy, with the major shows having more than 500 entries in a single age division. Purses in this type of event can exceed a total of $1 million. The nature of this aged event competition, with large purses in numerous events over a 4-year period, has caused the cutting horse economy to grow rapidly during the past several years. Select yearling and training sales are conducted annually that are beginning to parallel the racing industry in financial return on sales. This has contributed to the current popularity and resurgence of breeding of cutting and Western stock horses, which in turn will ensure the preservation of the tradition and heritage that this horse played in the history of the great Old West.

Lameness Examination

The increasing popularity of the cutting and reining horse for show and performance is occurring nationally and internationally. Sales of this type of horse have increased to Europe, South America, and other countries. In North America, the revival of interest stems primarily from excellent programs instituted by associations such as the National Cutting Horse Association and the National Reining Horse Association. These associations encourage owner participation at an amateur level in cutting and reining events. This type of performance horse creates a new diagnostic and treatment challenge for attending veterinarians, partially because of the rigid training schedules necessary for 3- to 6-year-old horses to compete in futurities and aged events.

Hindlimb lameness presents one of the more interesting diagnostic challenges to an equine clinician. The lameness is often difficult to diagnose and even more difficult to manage. A systematic approach must be developed to achieve an accurate diagnosis consistently. The veterinarian must use a routine that is repeated with each horse and must allow sufficient time to complete a thorough examination. Western stock horses may be difficult to evaluate while being led. These horses usually are not taught to lunge and are often difficult to trot in hand. A 10- to 15-m round pen with firm footing has proved to be beneficial for evaluating lameness.

Diagnosis and Management of Specific Lameness

Hindlimb lameness is more common than forelimb lameness in cutting horses. Mixed lameness with swinging and supporting components is common in hindlimbs, especially in upper limb lamenesses such as those involving the hock, stifle, and hip or sacroiliac region. Hindlimb lameness may be associated with two sources of pain: for example, chronic hock lameness and secondary lumbar and gluteal myositis. This section focuses on selected hindlimb lamenesses of the hock, stifle, and thoracolumbar regions.

Team Roping Horse

Historical Data and Decreased Performance

It is imperative for a clinician to know whether a team roping horse is used primarily as a heading or heeling horse. In addition, a thorough description of the owner’s complaint of a change in or decreased performance provides valuable insight into the underlying problem, bearing in mind that often in the early stages little or no lameness may be present. Eighty-nine of 118 (75%) team roping horses had a history of lameness, and 29 (25%) had an owner complaint of decreased or altered performance.¹ The type of performance change differed between horses used for heading or heeling (Figures 120-1 and 120-2).

Fig. 120-1 A header roping the steer and making a 90-degree turn to set the steer for the heeler. The weight of horse and rider results in excessive loading of the right forelimb of the head horse (gray horse).

Fig. 120-2 A heel horse stopping after the heeler throws his rope. Note the flexion of the hock joints during the stop and the extreme forward placement of both hindlimbs.

Diagnosis and Management of Specific Lameness

Palmar Foot Pain

Given the usual QH conformation of large body size and small feet or short, upright pastern conformation, navicular disease and injuries to structures within the palmar aspect of the foot are common. Right forelimb or bilateral palmar foot pain and left forelimb palmar foot pain were the most common problems identified in heading and heeling horses, respectively. Palmar foot pain results in a slowly progressive lameness, often bilateral, and horses may initially respond to intraarticular medication of the distal interphalangeal (DIP) joint, NSAIDs, and corrective shoeing. Soft tissue injuries of the palmar aspect of the foot (e.g., injury of the distal sesamoidean impar ligament [DSIL], a collateral ligament of the DIP joint, or the deep digital flexor tendon [DDFT] in the region of the navicular bone) are also common in heading horses and usually are acute, occurring during a roping event. Lameness is improved by perineural analgesia of the palmar digital nerves or intraarticular analgesia of the DIP joint. Often no radiological abnormality is apparent. Diagnosis of the specific structure injured can usually only be determined by magnetic resonance imaging (MRI).

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The diagnosis of palmar foot pain is not complicated, but determining which structure is damaged can be challenging. Diagnosis is based on a combination of historical data and the response to perineural and intraarticular analgesia, high-quality radiographs, and possibly advanced diagnostic techniques such as nuclear scintigraphy, computed tomography, or MRI. Severity and duration of the lameness, the horse’s activity, potential owner compliance, and the experience of the owner’s farrier should be considered when determining therapy. The horse’s hoof wall quality, conformation, environment, and occupation all affect treatment.

A thorough musculoskeletal examination should include palpation of the digital pulse amplitudes and assessing the hoof capsule for increased heat. In 97% of 23 horses with palmar foot pain there was increased digital pulse amplitude in the most severely affected limb. Hoof tester evaluation can be beneficial in determining pain location. Pain involving the navicular area is identified by application of intermittent hoof tester pressure over the middle third of the frog, which results in persistent nonfatigable reflex withdrawal of the hoof from the examiner. However, false-negative results may occur, especially during periods of dry weather when the horse’s feet are excessively hard or in horses with thick soles and hard frogs. It is important to assess whether the withdrawal reflex is resulting from real pain and not a whimsical reaction by the horse. The results from both front feet should be compared. Horses with an injury of the DSIL or the insertion of the DDFT seem particularly sore with hoof tester pressure near the junction of the middle and dorsal thirds of the frog. Horses with underrun heels, bruised heels, or damaged laminae in the heel area often have more pain over the affected heel. It is important, if possible, to differentiate peripheral versus central hoof pain with a thorough hoof tester examination.

Many of the middle-aged roping horses diagnosed with palmar foot pain have moderate to severe radiological lesions of the navicular bone. My initial treatment involves correcting any existing hoof imbalance. I apply a 2-degree wedge pad or wedge shoe, which decreases the pressure on the navicular area by about 25%. If the horse’s foot was imbalanced and/or poorly shod, then correcting these problems combined with systemic NSAID therapy (phenylbutazone 1 g twice daily for 10 days) and rest may temporarily resolve the lameness. If the owner cannot rest the horse or the feet are properly shod, then I medicate the DIP joint using a combination of 9 mg of triamcinolone acetonide, 10 to 20 mg of hyaluronan, and 125 mg of amikacin.² Postinjection care involves 4 to 5 days of no roping and NSAID therapy (phenylbutazone 2 g daily for 5 days). Approximately 60% of horses respond to DIP joint medication and, depending on severity of disease and level of work, will remain sound for 4 to 6 months. If the horse does not respond to DIP joint medication, then I medicate the navicular bursa with 10 mg of hyaluronan and 9 mg of triamcinolone acetonide, or if a severe bony lesion exists, I use 20 mg of methylprednisolone acetate plus 125 mg of amikacin. I reserve navicular bursa medication only for those not responding to DIP medication and known not to have an acute soft tissue injury (e.g., a DDFT lesion). Horses with chronic collateral sesamoidean ligament pathology, identified by the presence of a spur on the proximomedial or proximolateral aspects of the navicular bone, usually do not respond to DIP joint medication but do respond to treatment of the navicular bursa. I caution the owner that navicular bursa injections are invasive and may lead to subsequent DDFT pathology and/or rupture. Palmar digital neurectomy is the last resort in treating horses with palmar foot pain because of its short-lived results (average 2 years of soundness) and numerous complications, such as severe infection, DDFT rupture, and DIP joint subluxation.

Soft Tissue Injuries

Ligament or tendon injury occurred in about 15% of heading horses, especially in the right forelimb, and in about 10% of heeling horses, usually in the left forelimb.¹ The structure affected varied, but the suspensory apparatus, the accessory ligament of the DDFT, DDFT, superficial digital flexor tendon (SDFT), and the distal sesamoidean ligaments were all involved. These injuries usually cause lameness of varying degrees, and diagnosis by clinical examination is straightforward. Ultrasonography should be used to confirm the diagnosis. Distal sesamoidean ligament injury may be more difficult to diagnose but often results in acute, moderate to severe lameness (grade 2 to 3 of 5) after a run, associated with pain on palpation of the palmar aspect of the pastern. Perineural analgesia of the palmar digital nerves may improve the lameness, but analgesia of the palmar nerves at the base of the proximal sesamoid bones is needed for complete soundness. Fractures of the middle phalanx are also common; therefore the horse should be examined by radiography and ultrasonography. Ultrasonographic evidence of enlargement or reduction in echogenicity in the straight (SSL) or oblique sesamoidean ligaments (OSL) is diagnostic (Figure 120-3). Radiological examination is usually negative if lameness is acute; however, chronic injury is often associated with entheseous new bone on the palmar aspect of the proximal phalanx or on the proximopalmar aspect of the middle phalanx associated with OSL or SSL injury, respectively.

Fig. 120-3 Transverse (left) and longitudinal (right) ultrasonographic images of the midpastern region of the right forelimb of a head horse. There is a hypoechogenic lesion in the straight sesamoidean ligament (arrows) (SSL). SDFT, Superficial digital flexor tendon; DDFT, deep digital flexor tendon; OSL, oblique sesamoidean ligament.

In hindlimbs, deep digital flexor tendonitis, tenosynovitis of the digital flexor tendon sheath, and proximal suspensory desmitis (PSD) are common, especially in the left hindlimb of head horses. When turning to face the steer, the head horse turns 180 degrees at fast speeds, putting a rotational torque on the distal aspect of the left hindlimb (Figure 120-4).

Fig. 120-4 A head horse (right) turns to face the heeler at the end of the run. Note the strain placed on the left hindlimb.

The management of roping horses with these soft tissue injuries varies with which structure is affected and severity of the lesion, although the initial treatment is similar. The first 2 weeks consist of daily ice therapy for 20 minutes two to three times per day, NSAIDS (phenylbutazone 1 g twice daily for 7 days), stall rest with 10 minutes of handwalking, and a support bandage. This is followed by a variable period of stall rest with 15 to 20 minutes of daily handwalking. When the horse is sound and there is 80% resolution of any lesion seen using ultrasonography, a controlled exercise program is initiated to strengthen the affected structure (Box 120-1).

BOX 120-1 Exercise Regimen after Mild Injuries to Forelimb Suspensory Ligament or Accessory Ligament of the Deep Digital Flexor Tendon

Weeks 1-2	The horse is given stall rest or a small run (6 × 10 m) with support bandage on the limb, ice therapy, and nonsteroidal antiinflammatory drugs.
Weeks 2-6	Length of time depends on severity of the lesion and structure affected. Horses are rechecked and ultrasonographic examination is performed at 3-month intervals until the horse is sound and the lesion is 75% to 80% healed. The horse is handwalked 10 minutes daily.
Weeks 6-8	Confinement is continued with 15 minutes of handwalking twice daily.
Weeks 9-12	Confinement is continued with 30 minutes of handwalking daily.
Weeks 13-16	If horse is sound at the trot, then confinement is continued, but the horse is walked under saddle or is ponied 15 minutes a day plus 5 minutes of trotting. Five minutes of walking and trotting are added every third day. The horse is reexamined by ultrasonography before returning to roping activity.

The horse remains confined until the controlled exercise program is completed. Lameness and ultrasonographic examinations are repeated before the horse returns to roping activity or turnout.

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Distal Hock Joint Pain

OA of the distal hock joints is common, and heeling horses seem especially at risk. Most respond well to intraarticular medication of the centrodistal and tarsometatarsal joints. Middle-aged horses with moderate or severe OA are treated with 40 mg of methylprednisolone acetate and 125 mg of amikacin per joint. Younger horses or horses with mild to no radiological lesions are treated as above except 10 mg of hyaluronan is added to each joint. Postinjection care is 7 to 10 days off before returning to roping. The toes are squared on the hindlimbs to ease breakover and decrease torque on these joints.

Back and Pelvic Region Pain

Injury to the back and pelvic area is seen, especially in heading horses. Strain or tearing of the sacroiliac ligaments or epaxial musculature can occur. Radiographic evaluation is difficult and often unrewarding, but ultrasonographic examination may reveal longissimus lumborum and gluteal muscle tearing and can be used to evaluate the sacroiliac area. Lameness predisposing to back pain must be eliminated. Rest combined with topical heat (hot towels) and dimethyl sulfoxide or diclofenac (Surpass, IDEXX Pharmaceuticals, Inc., Greensboro, North Carolina, United States) helps many horses, but often months of rest are needed before the pain is eliminated. Treating the painful areas with local injections hastens the recovery time. I prefer a combination of 5 mL of methylprednisolone acetate, 5 mL of Sarapin, and 5 mL of prednisolone diluted with 30 mL of mepivacaine and then depositing 3 to 5 mL in several sites around the painful muscle or ligament. The horse is given 2 to 3 weeks of light riding, with no roping activity, and then is reevaluated by ultrasonography. Most horses return to roping activity within 4 weeks from the time of injury.

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Obviously all team roping horses are also susceptible to any of the same injury problems that other equine athletes experience. Most of these injuries produce overt lameness, and diagnosis is usually straightforward.

Calf Roping and Breakaway Roping Horses

Training Surfaces

The training surface has a strong influence on lameness in terms of incidence, degree of severity, and type of injury. In general, an arena or round pen is best constructed as follows: the original ground is graded to a 1.5% grade from one corner to the other and is compacted to 95%. A 15-cm thickness of base material such as limestone rock dust is then added, watered, and compacted to 95%. The type of base used is dictated by what is available in the area, but it should be smaller-sized particles (not small rocks) that have interlocking edges. A 1.5% grade should be maintained. Sand is then added to the top of the base to a thickness of at least 5 cm and not more than 12 cm in the arena, and from 10 to 15 cm in a round pen. Adding the sand at the minimum levels first and then adding more later if necessary is recommended. In general, less injury occurs with thinner layers of sand, but performance may be enhanced with thicker layers of sand. Fine beach sand is the best because it has low abrasive characteristics and is light. These qualities are important because the sand gets between the skin and protective boots and also comes in direct contact with the back of the pasterns and fetlocks. If the sand is coarse and abrasive, it damages the skin and causes lameness. The density of the sand is important because a horse has to push the sand during sliding stops, and if the sand is too heavy, it causes injury and destroys the horse’s confidence.

Water content of the training surface is also an important consideration. In general, applying water a few hours before use is a good idea, so that the water is distributed evenly. If the training surface is too deep with sand or if the base is not consistent, I see more soft tissue injuries such as tendonitis, suspensory injuries, curbs, and sprained backs. If the training surface is too hard, I tend to see bone injuries such as osteitis of the distal phalanx, navicular syndrome, sesamoiditis, or fractured proximal sesamoid bones.

The Relationship of Training to Lameness

The types of injuries commonly seen tend to vary as the training progresses. The young 2-year-olds have hoof and sole problems during the initial breaking process, before they are shod, associated with an increased digital pulse amplitude and sensitivity to hoof testers. Subchondral bone cysts in the medial femoral condyle and osteochondrosis of the fetlock may manifest at this time. Chip fractures, present but unnoticed when the horse was a foal or yearling, may become clinically apparent when ridden work starts.

The work during the latter half of training for a 2-year-old involves more speed and collection, and low-grade lamenesses may develop that later become persistent problems. These lamenesses include suspensory desmitis, navicular syndrome, and hock and stifle pain. The 3-year-old year involves even more collection, cow work at speed, and harder stops. We generally see a continuation of the 2-year-old problems, if they are not managed well, and also more acute injuries to soft tissue and chip fractures of the fetlock and carpus.

Conformation and Lameness

Conformation has an effect on the development of lameness, but I believe that conformation often is overemphasized. The component of conformation that has the biggest effect on soundness is body conformation and the degree of balance in motion. I have seen many horses whose conformation was not impressive when viewed at a standstill but were impressive when evaluated in motion. Balance in motion is that somewhat immeasurable quality that gives one the impression that the horse could jump, stop, turn, or do almost anything on any given stride without effort. In my experience, these horses remain sound while performing to an exceptional level, whereas horses that have less balance suffer more frequent injury. Although static conformation related to lameness is important and should be evaluated, in my opinion, conformation in motion is equally important.

The most common conformation problems that I see are toed in and toed out. These problems predispose the horse to lameness but are present to some degree in nearly all horses. Most often these conformational abnormalities are associated with injury to the suspensory ligament (SL) and also can be associated with injury to the collateral ligaments of the digit. I try to manage these conformation faults before they cause injury to the horse by trimming and shoeing. A horse that toes out initially contacts the ground with the outside toe quarter with improper trimming. The hoof then slides along the ground and begins to rotate the toe out. The inside heel bulb then makes contact with the ground, and the hoof rotation stops. However, this rotational force continues up the limb and places unnatural strain on the soft tissues below the carpus and eventually causes damage. I recommend removing more wall from the hoof at the point of contact and beveling the toe so that breakover is accomplished easily over a wide area. My goal is to get the entire hoof to contact the ground evenly and eliminate the rotational force. Horses that toe in generally contact the ground at the inside toe quarter. Horses with this problem need more hoof removed from the inside toe, the goal being to cause the foot to land flat.

Lameness Evaluation

I begin the lameness examination by obtaining as complete a history as possible. I establish the duration of lameness; any change in lameness, if the horse has been rested or kept in work; any response to treatment; alteration in lameness with work; when the horse was last trimmed and shod; any changes in footing, type of work, or shoeing; if lameness was associated with turnout or work; if the horse has received any intramuscular injections; if the horse kicks the paddock or stall; if the horse is turned out with others; if the horse stumbles; any known trauma; whether the lameness occurred insidiously or suddenly; and if the horse stands normally. Generally, the best history is obtained from the grooms and trainer, although some owners can provide information.

I watch the horse at the walk, trot, and canter, loose in a 9-m round pen, and on firm footing on a 2% slope. The degree of lameness often is amplified when the horse is loose, on hard ground, and allowed to work on a slight slope. Some lameness characteristics are best seen at a slow trot and some at an extended trot. The round pen enables one to evaluate the horse’s ability to hold leads. Detecting low-grade ataxia is also easier when the horse works free, especially during downward transitions.

Lameness may be manifest in how a horse does a sliding stop; lameness may be accentuated after several sliding stops from a canter. A horse may slide stronger on one hindlimb than the other. The complaint is often made that a horse is not stopping as well as previously, although lameness is not noticed. A horse may begin a sliding stop normally but then pick up the painful limb halfway through the stop and replace it. The stop is not held evenly. The stop becomes normal if pain is removed by local analgesia.

Another common situation occurs when a horse is cutting a cow; the horse runs off at one end or does not come back with the cow as strongly at one end. The hindlimb farthest from the cow before the weak turn is generally the lame limb. If this horse is asked to do rollbacks in a round pen, the horse is much weaker when it reverses direction one way. Generally, the hindlimb on the outside of the circle after the weak rollback is the lame limb.

Competition is now so great that the difference between winning and losing is sometimes a matter of which horse feels the best. Performance diminishes before outright lameness is noted. Hindlimb lameness is particularly common in reined cow horses because of hock or stifle pain or proximal suspensory desmitis.

Flexion tests include flexion of the digit in all limbs and carpal, hock, and stifle flexions. Notes are made on the results and whether the horse resented flexion. The digit is flexed in an oblique plane (applying medial and lateral torque), and any resentment or decreased elasticity is noted.

All the soft tissue structures are palpated, and any enlargements and sensitivity are noted. Hoof testers always are applied to the front feet, as well as to the hind feet of horses with hindlimb lameness. Any lameness or weakness is classified in degrees (grade 1 to 5); by the limb involved; by weight bearing or non–weight bearing or mixed status; by the effect of walking in a circle or on a straight line, on an incline or decline; by flexion tests; and by the effects of prolonged digital pressure over sensitive areas.

If lameness is serious enough possibly to be caused by fracture, radiography is performed first; otherwise, diagnostic analgesia is used to establish the source of pain. Intraarticular analgesia is more specific than regional analgesia, which can be done at a later time if necessary; therefore I often start with intraarticular blocks, especially in forelimbs. I rely on the flexion tests to direct the start point. If flexion of the distal limb is normal but carpal flexion is positive, I usually use perineural analgesia of the proximal palmar metacarpal and palmar nerves (high four-point). If lameness persists, I perform intraarticular analgesia of the carpus. If flexion of the distal limb is positive, I perform intraarticular analgesia of the distal interphalangeal (DIP) joint first and then proceed to the pastern and fetlock joints if necessary to eliminate the pain causing lameness. If intraarticular analgesia is not helpful and the flexion test is still positive, I perform perineural analgesia of the palmar digital nerves, followed by the digital nerves at the base of the proximal sesamoid bones (PSBs) and later a “low four-point block.” Knowing whether the problem is articular is useful because horses with articular problems are often more amenable to treatment.

For intraarticular analgesia I do a three-step povidone-iodine (Betadine, Purdue Products L.P., Stamford, Connecticut, United States) and alcohol skin preparation and use sterile gloves. I place a subcutaneous bleb of local anesthetic solution before injection and combine local anesthetic solution with gentamicin sulfate (40 mg).

In a hindlimb I usually use perineural analgesia proximal to the fetlock, local infiltration around the region of the origin of the SL, intraarticular analgesia of the centrodistal and tarsometatarsal joints separately, and intraarticular analgesia of the femoropatellar and medial femorotibial joints. The lateral femorotibial compartment rarely is involved. If the response to a low four-point block is positive but the response to plantar nerve blocks at the base of the PSBs is negative, intraarticular analgesia of the metatarsophalangeal joint is performed the following day.

Imaging Considerations

Once the region of pain is localized, the area is examined using radiography and ultrasonography to identify the exact structure that has been damaged and to assess the degree of damage. The more specific I can be at this point, the more reliable the prognosis and treatment are. If the diagnosis is not specific, scintigraphy often is used. Generally, a differential diagnosis list is generated based on the physical examination. Developing a therapeutic plan based on a tentative or vague diagnosis is a mistake. Nearly all diagnoses are tentative until the pain has been localized as specifically as possible through the use of diagnostic analgesia and appropriate imaging.

Proceeding without a Diagnosis

Sometimes the site of pain causing lameness cannot be discovered, even after all the joints and nerves have been blocked and a complete scintigraphic examination has been performed. I then treat the horse for myofascial pain with drugs or chiropractic therapy. If the horse responds to these therapies, then this is indirect evidence of the cause. Another possible cause is equine protozoal myelitis (EPM). Horses with EPM may show chronic lameness without other neurological signs.

Lameness and Shoeing Considerations

Proper foot balance is critical to resolving all lameness problems successfully. The foot should be trimmed to land evenly. Any medial-to-lateral imbalance should be removed by trimming. If the point of contact is the lateral toe quarter, then enough of the lateral wall should be removed so the foot lands flat. The foot should be trimmed or a wedge used to achieve a hoof angle that is the same as the pastern angle (about 55 degrees in forelimbs and 57 degrees in hindlimbs). A square-toed shoe that has a wide bevel, which extends from the medial to lateral toe nail holes, commonly is recommended and is useful. The shoe should be set back so the dorsopalmar axis is shortened. The heels are trimmed so the shoe comes in contact with the wall at the widest section of the frog. These specifications are designed to remove rotational forces up the limb that occur in horses with medial-to-lateral imbalances, to provide mechanical advantage to the palmar/plantar aspect of the limb that occurs in horses with a long toe and low heel, and to reduce concussion to the digit that occurs in horses with the two-phase foot impact associated with foot imbalance.

An egg bar shoe is used for horses with moderate to severe tendonitis, suspensory desmitis, or an apical PSB fracture. A reverse shoe is used sometimes for horses with navicular syndrome, ringbone, sesamoiditis, suspensory desmitis, tendonitis, constricted palmar/plantar annular ligament, carpitis, and tarsitis. Horses with bruising in the sole are shod with soft dental acrylic pads. Horses with heel and quarter cracks are managed with egg bar shoes.

Ten Most Common Lameness Conditions in the Reined Cow Horse

Treatment of Lameness

Conformation

Horses are predominately American Quarter Horses (QHs) and Appendix horses (QH and Thoroughbred [TB] crosses), but occasionally TB, Paint, or Arabian horses are seen. Speed, quick acceleration, and agility to slow down quickly to turn the barrel are essential. Many barrel horses have QH racehorse pedigrees. Some prefer stockbred horses, which usually have a calmer personality. Geldings are preferred. Horses usually range from 14.3 to 15.1 hands. Barrel horses are not usually as muscular and wide based as calf roping horses. They usually have long, leaner muscle mass that provides the speed and flexibility needed to perform the 360-degree turns. In a recent retrospective study evaluating musculoskeletal problems in 118 horses used solely for barrel racing, the median age was 9 years (range, 3 to 19 years), median weight was 509 kg (range, 409 to 611 kg), and 73% were geldings and 27% were mares.⁶

Training

Futurity competitions are popular because of the amount of prize money, and training usually starts at 2 years of age. Futurity horses often have short careers because of the pressure to perform at a high level of competition at only 4 to 5 years of age, resulting in advanced osteoarthritis (OA), often in the distal tarsal joints. Successful futurity horses seldom have long-term careers because of behavioral problems or performance-limiting injuries.

Horses that are 5 years of age or older, started slowly, and are allowed to mature before performing in serious competition may compete professionally for 5 years.² The average age of a professional barrel horse is 10 to 15 years. Horses may compete in 50 to 100 rodeos per year and spend much time traveling. An experienced barrel horse is trained by practicing turns but rarely uses the barrels because the horse learns to anticipate the pattern and tires of it. Many professional horses are ponied (led from another horse) or are ridden just enough to keep them fit for competition, but they are never really worked unless competing.

Older, semiretired horses that are well trained to the barrel pattern, but not fast enough for upper-level competition, may be used for a child or beginner. These horses do make repetitive barrel pattern runs in a practice pen for the rider to learn and often have use-related injuries, requiring much maintenance therapy to withstand the number of practice runs needed to teach a beginner.

Historical Data and Poor Performance

Barrel racing is the one equine discipline that most riders train and ride their own horses. Unlike roping events where many variables exist (e.g., cow selection and partners), there are few variations in the barrel horse pattern or run. Size of arena and ground surface may affect the speed of the run, but the barrel pattern is constant, and most riders know what time to expect from their horse for a given arena size. Therefore more barrel horses are examined because of a change or decrease in performance (40%) compared with roping horses (about 25%), rather than overt lameness. In a recent study, 45% of barrel horses that had an owner complaint of running past or wide around the first (right) barrel had a right forelimb musculoskeletal problem.⁶ Unilateral or bilateral forelimb foot pain or subclinical epistaxis was observed in horses that had a recent decrease in speed. Horses that were reluctant to turn to the left had either a left forelimb or hindlimb musculoskeletal problem.

Other musculoskeletal problems depend on the horse’s age and level of competition. A young futurity barrel horse may run up the fence, that is, the horse does not turn around the barrel but runs past it up the arena, or it may refuse to enter the arena. No lameness may be detectable, and the veterinarian has to determine whether the young horse is mentally stressed and showing behavioral problems or is responding to pain. Several options are presented to the owner to help determine whether the horse is responding to pain or it is a result of overtraining. One option is to administer phenylbutazone (2.2 mg/kg daily for 2 weeks and then 1.1 mg/kg daily for 2 weeks) for 30 days and to keep the horse in barrel race training. If the horse returns to normal performance, then it is concluded that the horse is most likely experiencing pain. If the problem does not resolve, then I try to address any behavioral problems. If problems persist, I often suggest giving the horse a 3- to 6-month break from barrel racing and have the horse work cattle or perform other less intense activities. A second option is to increase the workload and try to establish whether lameness can be identified and then located with diagnostic analgesia, but few owners select this option. Older, experienced horses usually have pain-related problems.

Most barrel racers train their own horses, and the quality of training is inconsistent, and performance changes may be induced by the rider. Determining which barrel is the problem barrel is helpful. An owner may complain that the horse will not stay in the ground for the first barrel but works fine for the second and third barrels. The horse may perform well for the first barrel but does not make a good turn around the second barrel. The first barrel (usually going to the right) is the hardest barrel and most often a problem because the horse is running at full speed when it reaches the barrel and must slow quickly to make the 360-degree turn. When the horse is turning the barrel, the inside forelimb and hindlimb appear to be under the greatest pressure (Figure 120-6). If the owner complains that the horse is swinging wide or pulling away from the first barrel, the horse does not want to turn to the right and is probably trying to avoid right hindlimb or right forelimb pain.

Fig. 120-6 A barrel horse turning a barrel. Note the pressure on the inside hindlimb. This horse is on the backside of the barrel coming out of the turn and is in correct position. At this point in the barrel turn, a horse with hindlimb pain becomes uncollected and swings wide around the barrel.

The teeth are always evaluated to eliminate bitting problems as a cause of performance changes.

Lameness Examination

A barrel horse does not run at top speed over long distances like flat racehorses; therefore fatigue-type injuries like superficial digital flexor tendonitis or fetlock and carpal chip fractures are seen less commonly than in racehorses. Some of the common injuries seen in barrel horses are attributed to the twisting and turning motion of the horse at high speeds (see Figure 120-6).

In a recent study, the most common musculoskeletal problem observed in horses used solely for barrel racing was (1) forelimb foot pain (33%), with the right front more often affected; (2) OA of the distal tarsal joints (15%); (3) suspensory branch desmitis or tendon injury (14%); (4) a combination of foot pain and distal tarsal pain (12%); and (5) medial femorotibial joint pain (10%).⁶

If an obvious lameness is not detected when trotting the horse in a straight line or large circle, the horse is trotted in hand in a small circle (1.5- to 3-m radius), mimicking the barrel turn, which will exacerbate the lameness. This may be the only time the horse shows lameness.

Diagnosis and Management of Specific Lameness

QHs and Appendix QHs make up most of the barrel horses. Sore feet, navicular area pain, and palmar foot pain are the most frequent causes of forelimb lameness, with poor hoof conformation and farriery and hard arena surfaces being predisposing factors. Diagnosis and management are similar to those described for the team roping horse.

Distal hock OA is the second most common musculoskeletal problem and most common hindlimb problem most resulting in reduced performance or lameness. Diagnosis is based on intraarticular analgesia, radiology, response to treatment, and sometimes nuclear scintigraphy. The centrodistal and tarsometatarsal joints are treated using methylprednisolone acetate (40 to 60 mg/joint) or triamcinolone acetonide (6 mg/joint) alone or in combination with hyaluronan (10 mg/joint) plus 125 mg of amikacin. Ideally the horse should have 7 to 10 days of turnout or light exercise before returning to barrel racing, but often the competition schedule does not allow this. Response to treatment may take up to 3 weeks. If the horse does not respond to treatment, we reevaluate the horse for lameness.

Hindlimb proximal suspensory desmitis (PSD) and suspensory branch desmitis are common in older, seasoned horses and can be career-ending injuries. Deep sand in arenas may contribute to the high incidence. Moderate lameness (grade 2 to 3 of 5) often is exacerbated by upper limb flexion. The horse usually has no swelling or minimal swelling and no heat and pain for proximal suspensory body lesions, but these will be seen in horses with suspensory branch desmitis. Local analgesia is essential to verify the source of pain. Radiology of the proximal metatarsal area is often negative, although if the condition is chronic, endosteal reaction or entheseous new bone may be present, seen as increased radiopacity. Ultrasonographic examination may reveal an enlarged and hypoechogenic SL, but some horses have no detectable structural abnormalities. The latter are treated by local infiltration of triamcinolone acetonide (9 to 12 mg) and reduced work. With acute, mild PSD, horses often return to work in 2 to 4 weeks. I also recommend confining the horse to a small area to avoid further damage from excessive uncontrolled exercise. If ultrasonographic abnormalities are detected, the horse is confined to a small area (12- × 30-foot [3.7 × 9.1 m] run) with no riding for 60 to 90 days before reexamination. Complete healing often takes 6 to 12 months, and some horses never return to full athletic function. After the initial 2 weeks of ice therapy, rest, nonsteroidal antiinflammatory drugs, and support bandages, the horse is reevaluated. If the lesion is extensive or severe (type 2 or greater on a scale of 0 to 4), then novel tissue healing therapies such as platelet-rich plasma (PRP) or stem cells are injected into the lesion under ultrasonographic guidance to enhance quality of ligament fiber repair. I have had more experience with PRP and prefer it to stem cell therapy, but both may be beneficial in ligament healing. Hindlimb PSD can be difficult to treat because of the constricting thick fascia surrounding it. If the horse is not sound after 4 to 6 months (depending on severity of lesion) of confinement, then I have had good success performing a fasciotomy and neurectomy of the deep branch of the lateral plantar nerve. Postsurgery care consists of 60 days of stall rest with 20 minutes of daily handwalking and 60 days of controlled exercise program before returning to barrel racing or turnout activity.

PSD is also common in forelimbs. Deep arenas and long toes and low heels are predisposing factors. The prognosis for barrel racing horses with forelimb PSD is good, with most horses responding well to rest and controlled exercise for 3 to 4 months. Tendon protection boots are recommended.

Medial femorotibial joint pain also frequently occurs and is treated in a similar manner as described above for cutting horses (see page 1167). If the lameness is recurrent after several intraarticular injections, diagnostic arthroscopy is recommended. Metacarpophalangeal joint synovitis results in mild lameness (grade 1 to 2 of 5) that is exacerbated by fetlock flexion. The horse often strongly resists fetlock flexion. Lameness and response to fetlock flexion are eliminated by intraarticular analgesia. Radiology is usually negative. The horse is treated with intraarticularly administered triamcinolone acetonide (6 mg) and hyaluronan (20 mg). The problem may or may not recur. If recurrence is frequent, diagnostic arthroscopy is recommended.

Many times horses have undergone several types of alternative therapies (e.g., equipment changes, acupuncture, chiropractic, and herbal therapy) in an attempt to correct the perceived problems before being checked by a veterinarian. Often, for some inexplicable reason, an accurate diagnosis and conventional medical therapy are sought only after failure of these other treatments. Many owners rely on diagnosis from a fellow competitor and request treatment that was successful in another horse. This makes client communication difficult.

Shoeing Considerations

Traction, especially in the deep and often muddy arenas in which horses compete, is critical. A rim shoe is used most commonly on all feet, with one rim higher than the other to provide added traction. A rounded toe provides easier breakover than a normal flat steel shoe. Hind shoes may have square toes.

Recently the natural balance shoe has gained popularity as owners are becoming more aware of good farriery principles and are trying to correct long-toe, low-heel problems. The natural balance shoe is available in steel or aluminum. Steel construction is preferred because of the added weight, which provides better traction than an aluminum shoe. The natural balance shoe has a rockered toe that eases breakover of the forelimb and is built with a wider web than a normal shoe, which benefits a sore-footed horse competing on hard surfaces.

Other Considerations

Exercise-induced pulmonary hemorrhage is common in barrel horses. The owner may complain that the horse has lost a step or has become slower. If a musculoskeletal reason for the performance change cannot be determined, a respiratory evaluation is indicated. Obvious bleeding from the nostrils rarely is seen, but endoscopic examination within 30 minutes of the barrel race often reveals tracheal hemorrhage. Presently no drug testing or rules prevent drug administration for competition. Most horses receive phenylbutazone or flunixin meglumine 4 to 6 hours before competition and furosemide (4 to 8 mL/horse).

Ten Most Common Lameness Conditions in 2- to 8-Year-Old European Western Performance Horses

Lameness of the Foot

Common causes of foot pain include subsolar abscessation, solar bruising, osteoarthritis (OA) of the distal interphalangeal (DIP) joint, osteitis or fracture of a palmar process of the distal phalanx, and navicular syndrome. Oblique radiographic images of the palmar (plantar) processes of the distal phalanx and a palmaroproximal-palmarodistal oblique image of the navicular bone are particularly valuable.

Poor foot conformation is often an important predisposing factor for the development of foot pain. The foot is often upright with overgrown angles of the wall and heel, flattening of the sole at the toe, and an underdeveloped frog. Bar shoes exacerbate high heel conformation because they prevent the heel bulbs from sinking into the ground; the bar of the shoe concentrates loading and reaction forces from the ground in the bars and underlying structures inducing palmar foot pain.

In such horses trimming of the bars and wall at the heel increases the length of the loading plane, thus distributing ground reaction forces over a wider area. If the horse works on soft ground, reaction forces on the palmar aspect of the foot can be reduced by applying aluminum shoes with thinned and beveled heels; if the horse works on harder ground, a complete pad must be inserted between the shoe and the foot, and the shoe must be well concaved on the inner surface to prevent direct pressure to the sole through the pad itself. Shearing forces at the toe can be decreased by moving the breakover point back with a rolled-toe shoe.

Most of the top-level reining QHs are now shod with premade aluminum shoes beveled along the entire outer surface (Figure 120-7; Colleoni/Zaffi design, Farrier Product Distribution, Shelbyville, Kentucky, United States). These are available in either an open or bar type. The beveled outer surface helps the foot to breakover in most of the demanding figures (like spins or roll backs) that produce marked oblique and twisting forces on the distal aspect of the limb. A rocker toe shoe or squared toe is used less frequently because it can restrict the length of the stride.

Fig. 120-7 A typical shoe used in reining horses is made of aluminum and is beveled along the entire outer surface to reduce torsional forces associated with sudden turns and spins.

Treatment of reining horses with navicular syndrome during the show season is challenging because of the long detection times of most commonly used drugs either for local injection or for oral use. Horses with navicular syndrome often have long toe and underrun heel conformation. Treatment involves restoration of a more correct hoof-pastern axis and use of an egg bar or bar shoe to increase the loading area of the foot. A bar shoe also prevents the heel from sinking into the ground and reduces tension on the deep digital flexor tendon. Tendon lesions usually occur toward the insertion. Some are detectable ultrasonographically, but magnetic resonance imaging (MRI) is superior for diagnosis.

The hind feet are subject to enormous loading and twisting forces when horses perform quick stops or when spinning or doing a roll back. Reining horses are shod behind with sliding plates (sliders), which are usually kept long at the heels. A long-heeled shoe concentrates load at the angle of the heel and can create resistance to turning.

Lameness of the Hock

Lameness associated with tarsocrural joint is infrequent; however, many veterinarians still inject all three compartments of the hock routinely, thus increasing chances of articular reaction and infection.

OA of the distal hock joints is common. In 2-year-olds there is a high prevalence of partial collapse of the central and third tarsal bones with secondary OA. This is usually accompanied by a camped-under, sickle-hocked, or cow-hocked conformation of one or both hindlimbs.

I use a hock torsion test to try to differentiate pain arising from the centrodistal or tarsometatarsal joints. With the hock in a semiflexed position, I apply a medial to lateral rotational force on the longitudinal axis of proximal aspect of the third metatarsal bone. If the horse reacts quickly or tries to kick, this indicates centrodistal joint pain, whereas if the reaction is slower and the horse gradually lifts and abducts the limb, the test suggests tarsometatarsal joint pain. The hock torsion test is not the “Churchill test.” When performing the torsion test there must be neither direct compression on the medial aspect of the hock nor any compression of the suspensory ligament (SL).

Treatment of horses with OA of the distal hock joints is by intraarticular administration of corticosteroids and sodium hyaluronan. Care must be taken with withdrawal times for horses competing under FEI rules. Horses refractory to intraarticular medication are treated by surgical (drilling) or chemical (sodium monoiodoacetate or ethyl alcohol) arthrodesis. Arthrodesis is most effective in 2-year-olds.

Tenosynovitis of the long digital extensor tendon sheath on the dorsolateral aspect of the tarsus may result in a shortened cranial phase of the hindlimb stride. Ultrasonographic examination of the sheath may reveal tendon lesions and extensive tenosynovial adhesions (Figure 120-8). Treatment involves intrathecal injection of corticosteroids. If chronic, tenoscopic debridement of adhesions and partial retinacular release are indicated.

Fig. 120-8 Longitudinal ultrasonographic image of the long digital extensor tendon sheath on the dorsolateral aspect of the hock. Proximal is to the left. There is extensive echogenic material covering the extensor tendon and echogenic bands (arrows) extending between the tendon and the synovium.

Superficial Digital Flexor Tendonitis

Acute superficial digital flexor tendonitis is a common cause of lameness in 2-year-old reining and cutting horses. Chronic injuries are seen in older horses that have not received proper treatment of acute lesions. Two groups of horses are predisposed to superficial digital flexor tendon (SDFT) injury: (1) young thin-legged Appaloosas, Paints, and QHs with conformation defects such as tied in below the knee, offset knees, and calf knees; and (2) well-built 3-year-old QHs intensely trained, especially working on spins in preparation for the futurity.

Lesions almost invariably affect the most lateral or medial border of the SDFT, usually extending for 3 to 5 cm in the middle or distal third of the metacarpal region, and are seen as diffuse areas of reduced echogenicity (Figure 120-9). Extreme uneven loading of the medial or lateral side of SDFT occurs while the horse is spinning or performing rapid turn backs. To reduce leverage and shearing forces acting on a hoof’s quarters in the breakover phase of the spin, top-level reining QHs are currently shod with aluminum shoes beveled along the entire outer surface (see Figure 120-7).

Fig. 120-9 Transverse ultrasonographic image of the distal metacarpal region of a 3-year-old Quarter Horse filly in full training. Medial is to the left. There is an acute anechogenic lesion of the lateral aspect of the superficial digital flexor tendon, which is swollen.

Treatment of horses with acute tendon lesions is aimed at reducing inflammation and edema with rest, cold packs, poultice, stall bandage, oral nonsteroidal antiinflammatory drugs followed by peritendonous injection of low doses of short-acting corticosteroids mixed with antiedema drugs. Intralesional, ultrasound-guided injection of platelet rich plasma (PRP) is performed 10 to 14 days after injury. For acute SDFT lesions in reining or cutting QHs, it is recommended that the horse should not return to full athletic function until at least 8 months after injury.

Lameness of the Stifle

Stifle pain is caused by subchondral bone cysts in the medial femoral condyle, traumatic OA, medial collateral ligament injury, osteochondrosis of the femoral trochleas, and fragmentation of the distal aspect of the patella in horses that underwent previous medial patellar desmotomy.

Digital radiography has enhanced the ability to detect subtle alteration in shape of the joint surface of the medial femoral condyle and early changes of subchondral bone opacity in early stages of the disease.

Intraarticular therapy should avoid use of the depot form of corticosteroids because it has been associated with rapid progression of OA and persistent lameness associated with the medial femorotibial joint in reining and cutting QHs. Surgical management of horses with medial femoral condyle cysts using arthroscopically guided injections of methylprednisolone acetate into the cyst lining or curettage results in a 50% to 60% chance for return of the horse to previous level of competition. Rest for 6 to 8 months is mandatory.

Suspensory Desmitis

Proximal suspensory desmitis (PSD) and desmitis of the branches of the SL are common. PSD affects young reining and cutting QHs in early or advanced training. Lameness is usually intermittent and can vary in intensity from grade 1 to 3 of 5, depending on workload; the horse is lamer with the affected limb on the outside of the circle. Lameness is abolished with analgesia of the lateral palmar nerve. Subtle ultrasonographic changes can be difficult to identify, and comparison with the contralateral limb is useful. Radiology is useful for identification of increased opacity in the proximal aspect of the third metacarpal/metatarsal bone.

Treatment of horses with PSD is based on rest, intralesional injection of PRP, shock wave therapy, radiotherapy/hyperthermia (INDIBA, Sant Cugat del Vallés, Barcelona, Spain). Corrective shoeing comprises an open aluminum shoe wide at the toe and thinned and beveled at the heels. A horse with an uncomplicated PSD lesion requires 90 days of convalescence. The presence of increased bone opacity at the origin of the SL is a poor prognostic indicator, with many horses remaining chronically lame.

Desmitis of a branch of the SL is frequently induced by medial-to-lateral foot imbalance; the wall is lower on the lateral side, and this induces more tensile stress on the lateral branch of the SL. Affected horses often have an offset knee or carpus valgus/fetlock varus and toe-in conformation.

Ultrasonographic examination often reveals hypoechogenic lesions of the most axial part of the branch. Therapy consists of periligamentous injection of corticosteroids and antiedema drugs and intraarticular treatment of the fetlock joint. Horses with chronic branch desmitis are treated with shock wave therapy, hyperthermia, controlled exercise, and repeated local application of working blisters. Shoeing correction involves the use of an open aluminum shoe with wider web on the side of the injured SL branch and balancing the foot.

Lameness of the Fetlock Joint

Osteochondrosis is frequent in front and hind fetlock joints. Most lesions in the dorsal aspect of the joint involve the sagittal ridge of the third metacarpal (McIII) or metatarsal (MtIII) bones, whereas lesions of the palmar (plantar) aspect originate from palmar (plantar) processes of the proximal phalanx.

OA of the fetlock joint is frequently accompanied by insertional desmitis of the SL branches or desmitis of the SL body at the level of its bifurcation. Both the fetlock joint and the SL must be treated for a successful outcome. Chronic synovitis may result in supracondylar lysis in 2-year-old QHs. Scintigraphy can be useful for identification of increased radiopharmaceutical uptake in the palmar aspect of the condyles of the third metacarpal bone, reflecting bone trauma in horses with no detectable radiological abnormality.

Western performance horses with early fetlock joint OA are managed using serial intraarticular injections with sodium hyaluronan, polysulfated glycosaminoglycans or interleukin-1 receptor antagonist protein (autologous conditioned serum). The prognosis is good. However, if there is thinning of articular cartilage and subchondral bone sclerosis or the presence of cystic lesions in the distal aspect of the condyles of the third metacarpal or metatarsal bones, the prognosis is poor, irrespective of medical or surgical treatment.

Lameness of the Carpus

Faulty conformation of the carpi is often present, especially offset knees. Lesions of the carpus include OA of the antebrachiocarpal and middle carpal joints, self-induced trauma of either the accessory carpal bone or the dorsal aspect of the carpus incurred during hard spinning, tenosynovitis of the carpal sheath, chip fractures of the radial or third carpal bones, increased radiopacity (sclerosis) of the radial facet of the third carpal bone, or sagittal fracture.

Sclerosis and sagittal fracture of the third carpal bone are the result of shearing forces caused by uneven loading of the medial aspect of the third carpal bone produced by repeated spinning and galloping in small circles.

Exostosis of the Second or Fourth Metacarpal/Metatarsal Bones (Splints)

Medial splints are common in 2-year-old reining and cutting QHs, frequently associated with a carpus valgus or offset knee conformation; lateral splints are less common but are occasionally seen in horses with an offset third metacarpal bone and base-narrow conformation.

Splints usually produce transient lameness, but horses with chronic lameness can be managed by freeze firing to reduce local pain and lameness. Shin splints—bony swelling on the proximal dorsomedial aspect of the McIII—are occasionally seen in very hard-stopping horses. The swelling is caused by periosteal and endosteal reaction to microfractures produced by repeated compression cycles of the dorsal cortex of the MtIII. Treatment is rest and handwalking for 30 to 45 days and freeze firing to reduce swelling and pain.

Curb

Curb is seen in 2-year-old QHs that have a sickle-hocked/cow-hocked conformation as a result of partial collapse of cuboidal hock bones. Ultrasonographic examination helps to determine which tendonous or ligamentous structure is involved and to decide the appropriate treatment.

Fracture of the Plantar Process of the Middle Phalanx

A fracture of the medial plantar process of the middle phalanx is the result of an avulsion caused by extreme pulling of the distal enthesis of the insertion of the SDFT during a stop. The tension in the medial branch of the SDFT may be the result of the wide stance of the hindlimbs that some horses adopt during the last phase of a sliding stop.

Shoeing should aim to correct horses that stop too wide by an inward rotation of the shoe or by applying medial heel extensions (trailers). Surgical management of horses with this middle phalangeal fracture by internal fixation with compression screws has had disappointing results. Prognosis is also poor following digital neurectomy and prolonged rest. Arthrodesis of the proximal interphalangeal joint might be a better choice.