Lower Limb

Bones

The femur, the longest bone in the body, is the bone of the thigh. It is slightly bowed anteriorly and runs slightly diagonally, lateral to medial, from the hip to the knee (Fig. 6-9 and Table 6-6). Proximally the femur articulates with the pelvis, and distally it articulates with the tibia and the patella (kneecap), which is the largest sesamoid bone in the body. The proximal femur is supplied with blood from the medial and lateral femoral circumflex branches of the deep femoral artery (see Fig. 6-13), an acetabular branch of the obturator artery, and by anastomotic branches of the inferior gluteal artery. The shaft and distal femur is supplied by femoral nutrient arteries and by anastomotic branches of the popliteal artery, the distal continuation of the femoral artery posterior to the knee.

Clinical Focus 6-7   Fractures of the Shaft and Distal Femur

Femoral shaft fractures occur in all age groups but are especially common in young and elderly persons. Spiral fractures usually occur from torsional forces rather than direct forces. Fractures of the distal femur are divided into two groups depending on whether the joint surface is involved. If reduction and fixation of intraarticular fractures are not satisfactory, osteoarthritis is a common posttraumatic complication.

Anterior Compartment Thigh Muscles, Vessels, and Nerves

Muscles of the anterior compartment exhibit the following characteristics (Figs. 6-10 and 6-11 and Table 6-7):

Additionally, the psoas major and iliacus muscles (which form the iliopsoas) pass from the posterior abdominal wall to the anterior thigh by passing deep to the inguinal ligament to insert on the lesser trochanter of the femur. These muscles act jointly as powerful flexors of the thigh at the hip joint (Table 6-7; see also Fig. 4-32).

Medial Compartment Thigh Muscles, Vessels, and Nerves

Muscles of the medial compartment exhibit the following characteristics (see Figs. 6-10 and 6-11 and Table 6-8):

The pectineus muscle, while residing in the medial compartment, is largely innervated by the femoral nerve, although it also may receive a branch from the obturator nerve. The adductor magnus, being an exceptionally large and powerful muscle, also receives some innervation via the tibial portion of the sciatic nerve, which runs in the posterior compartment of the thigh.

Posterior Compartment Thigh Muscles, Vessels, and Nerves

Muscles of the posterior compartment exhibit the following characteristics (Fig. 6-12 and Table 6-9; see Fig. 6-8):

Clinical Focus 6-8   Thigh Muscle Injuries

Muscle injuries are common and may include pulled muscles (muscle “strain,” actually a partial tearing of a muscle-tendon unit) from overstretching, or actual muscle tears, which can cause significant focal bleeding. Groin injuries usually involve muscles of the medial compartment, especially the adductor longus. Because the hamstring muscles cross two joints and are actively used in walking and running, they can become pulled or torn if not adequately stretched and loosened before vigorous use. Likewise, a “charley horse” is a muscle pain or stiffness often felt in the quadriceps muscles of the anterior compartment or in the hamstrings. Additionally, quadriceps muscle tears and tendon disruptions can occur, especially in athletes (see images).

Femoral Triangle

The femoral triangle is located on the anterosuperior aspect of the thigh and is bound by the following structures (see Fig. 6-10):

Inferiorly, a fascial sleeve extends from the apex of the femoral triangle and is continuous with the adductor (Hunter's) canal; the femoral vessels course through this canal and become the popliteal vessels posterior to the knee. The femoral triangle contains the femoral nerve and vessels as they pass beneath the inguinal ligament and gain access to the anterior thigh (see Fig. 6-10). Within this triangle is a fascial sleeve called the femoral sheath, a continuation of transversalis fascia and iliac fascia of the abdomen, that contains the femoral artery and vein and medially the lymphatics. Laterally the femoral nerve lies within the femoral triangle but outside this femoral sheath. The most medial portion of the femoral sheath is called the femoral canal and contains the lymphatics that drain through the femoral ring and into the external iliac lymph nodes. The femoral canal and ring are a weak point and the site for femoral hernias. The femoral ring is narrow, and consequently, femoral hernias may be difficult to reduce and may be prone to strangulation.

Clinical Focus 6-9   Diagnosis of Hip, Buttock, and Back Pain

Athletically active individuals may report hip pain when the injury may actually be related to the lumbar spine (herniated disc), buttocks (bursitis or hamstring injury), or pelvic region (intrapelvic disorder). Careful follow-up should examine all potential causes of the pain to determine whether it is referred and thus originates from another source.

Femoral Artery

The femoral artery supplies the tissues of the thigh and then descends into the adductor canal to gain access to the popliteal fossa (Fig. 6-13 and Table 6-10). The superomedial aspect of the thigh also is supplied by the obturator artery. These vessels form anastomoses around the hip and, in the case of the femoral-popliteal artery, around the knee as well (see Fig. 6-13).

Clinical Focus 6-10   Revascularization of the Lower Limb

Peripheral vascular disease and claudication can usually be managed medically by reducing the associated risk factors. However, patients who are refractory to medical management have the following invasive options:

• Percutaneous angioplasty: balloon dilation (with or without an endovascular stent) for recanalization of a stenosed artery (percutaneous revascularization)

• Surgical bypass: bypassing a diseased segment of the artery with a graft (1-3% operative mortality)

Clinical Focus 6-11   Femoral Pulse and Vascular Access

The femoral pulse is felt at about the midpoint of the inguinal ligament. The femoral artery at this point lies directly over or just medial to the femoral head, just lateral to the femoral vein and about a finger's breadth medial to the femoral nerve (see Figs. 6-10 and 6-13). The femoral artery and vein may be used to gain access to major vessels of the limbs, abdominopelvic cavity, and thorax (e.g., catheter threaded through femoral artery and into aorta for coronary artery angiography and angioplasty). Similarly, the larger veins of the inferior vena cava and the right side of the heart and pulmonary veins may be accessed through the femoral vein.

Thigh in Cross Section

Cross sections of the thigh show the three compartments and their respective muscles and neurovascular elements (Fig. 6-14). Lateral, medial, and posterior intermuscular septae divide the thigh into the following three sections:

Refer to the muscle tables to note several exceptions to these general divisions. However, learning the primary action and general innervation of the muscles by functional compartments will help you organize your study. Also, note that the large sciatic nerve usually begins to separate into its two component nerves—the tibial nerve and the common fibular nerve—in the thigh, although this separation may occur proximally in the gluteal region in some cases.

Knee Joint

The knee is the most sophisticated joint in the body and the largest of the synovial joints. It participates in flexion, extension, and some gliding and rotation when flexed. With full extension, the femur rotates medially on the tibia, the supporting ligaments tighten, and the knee is locked into position. The knee consists of the articulation between the femur and the tibia (biaxial condylar synovial joint) and between the patella and the femur.

Features of the knee joint are shown in Figures 6-16 (muscle tendon support), 6-17 and 6-19 (ligaments), 6-18 (radiographs), and 6-19 (bursae) and are summarized in Tables 6-12 and 6-13. Because of the number of muscle-tendon units running across the knee joint, several bursae protect the underlying structures from friction (Fig. 6-19). The first four of the bursae listed in Table 6-14 also communicate with the synovial cavity of the knee joint. The vascular supply to the knee primarily arises from genicular branches of the popliteal artery, the inferior continuation of the femoral artery (Fig. 6-13).

The innervation to the knee joint is via articular branches from the femoral, obturator, tibial, and common fibular nerves.

The proximal (superior) tibiofibular joint is a plane synovial joint between the fibular head and the lateral condyle of the tibia (Fig. 6-20). The joint is stabilized by a wider and stronger anterior ligament and a narrow weaker posterior ligament; this joint allows for some minimal gliding movement.

Clinical Focus 6-12   Multiple Myeloma

Multiple myeloma, a tumor of plasma cells, is the most malignant type of primary bone tumor. This painful tumor is sensitive to radiation therapy, and newer chemotherapeutic agents and bone marrow transplantation offer hope for improved survival. Fever, weight loss, fatigue, anemia, thrombocytopenia, and renal failure are associated with this cancer, which usually occurs in middle age.

Clinical Focus 6-13   Tibial Fractures

Six types of tibial plateau fractures are recognized, most of which involve the lateral tibial condyle (plateau). Most result from direct trauma and, because they involve the articular surface, must be stabilized. Fractures of the tibial shaft are the most common fractures of a long bone. Because the tibia is largely subcutaneous along its medial border, many of these fractures are open injuries. Often, both tibia and fibula are fractured.

Clinical Focus 6-14   Deep Tendon Reflexes

A brisk tap to a partially stretched muscle tendon near its point of insertion elicits a deep tendon (muscle stretch) reflex (DTR) that is dependent on the following:

• Intact afferent (sensory) nerve fibers

• Normal functional synapses in the spinal cord at the appropriate level

• Intact efferent (motor) nerve fibers

• Normal functional neuromuscular junctions on the tapped muscle

• Normal muscle fiber functioning (contraction)

Characteristically, the DTR usually involves only several spinal cord segments (and their afferent and efferent nerve fibers). If a pathologic process is involved at the level tested, the reflex may be weak or absent, requiring further testing to determine where along the pathway the lesion occurred. For the lower limb, you should know the following segmental levels for the DTR:

• Patellar ligament (tendon) reflex L3 and L4

• Calcaneal tendon reflex S1 and S2

Clinical Focus 6-15   Patellar Injuries

Subluxation of the patella, usually laterally, is a fairly common occurrence, especially in adolescent girls and young women. It often presents with tenderness along the medial patellar aspect and atrophy of the quadriceps tendon, especially the oblique portion medially derived from the vastus medialis. Patellar ligament rupture usually occurs just inferior to the patella as a result of direct trauma in younger people. Quadriceps tendon rupture occurs mostly in older individuals, from either minor trauma or age-related degenerative changes, including the following:

• Arthritis

• Arteriosclerosis

• Chronic renal failure

• Corticosteroid therapy

• Diabetes

• Hyperparathyroidism

• Gout

Clinical Focus 6-16   Rupture of the Anterior Cruciate Ligament

Rupture of the anterior cruciate ligament (ACL) is a common athletic injury usually related to sharp turns, when the knee is twisted while the foot is firmly on the ground. The patient may hear a popping sound and feel a tearing sensation associated with acute pain. Joint stability can be assessed by using the Lachman and anterior drawer tests. With an ACL injury, the tibia moves anteriorly (the ACL normally limits knee hyperextension) in the anterior drawer test and back and forth in the Lachman test.

Clinical Focus 6-17   Sprains of the Knee Ligaments

Ligament injuries (sprains) of the knee are common in athletes and can be characterized as:

• First degree: stretched ligament with little or no tearing

• Second degree: partial tearing of the ligament with joint laxity

• Third degree: complete rupture of the ligament, resulting in an unstable joint

Damage to the tibial collateral ligament may also involve a tear of the medial meniscus, as the meniscus is attached to the ligament. The “unhappy triad”—tears of these structures and the ACL—is usually the result of a direct blow to the lateral aspect of the knee with the foot on the ground.

Clinical Focus 6-18   Tears of the Meniscus

The fibrocartilaginous menisci are often torn when the knee undergoes a twisting injury. Patients complain of pain at the joint line, and the involved knee “gives way” when flexed or extended. Rupture of the tibial collateral ligament often involves a tear of the medial meniscus because the ligament and meniscus are attached.

Clinical Focus 6-19   Osgood-Schlatter Disease

Osgood-Schlatter disease (OSD) is a partial avulsion of the tibial tuberosity. During normal fetal development, the tuberosity develops as a distinct anterior segment of the epiphysis of the proximal tibia. After birth, this segment develops its own growth plate composed mostly of fibrocartilage instead of hyaline cartilage, the fibrocartilage perhaps serving as a means to handle the tensile stress placed on the tuberosity by the patellar ligament. The tuberosity normally ossifies and joins with the tibial epiphysis, but in OSD, repetitive stress on the tuberosity may cause it to separate (avulse) from the tibia. The avulsed fragment continues to grow, with the intervening space filled with new bone or fibrous connective tissue, so that the tibial tuberosity is enlarged. At times, a painful prominence occurs. OSD is usually more common in children who engage in vigorous physical activity than in less active children.

Clinical Focus 6-20   Osteoarthritis of the Knee

As with arthritis of the hip, osteoarthritis of the knee is a painful condition associated with activity, although other causes may also precipitate painful episodes, including changes in the weather. Stiffness after inactivity and decreased range of motion are common. With time, subluxation of the knee may occur with a varus (bowleg) deformity.

Clinical Focus 6-21   Septic Bursitis and Arthritis

Humans have more than 150 bursae in their subcutaneous tissues. With increased irritation, these bursae, which are lined with synovium and contain synovial fluid, produce more fluid until significant swelling and bacterial infection occur. The result is septic bursitis, characterized by the following:

• Heat over the affected area

• Swelling

• Local tenderness

• Limited range of motion

Septic arthritis occurs when infection gains entry to the joint space. If initial therapy fails, surgical debridement and lengthy antibiotic treatment may be needed.

Muscles, Vessels, and Nerves of the Dorsum of the Foot

The dorsum of the foot consists of two intrinsic muscles, the extensor digitorum brevis and the extensor hallucis brevis. These muscles function to extend the toes and are supplied by the anterior tibial artery from the leg via its dorsalis pedis branch (Fig. 6-29). A dorsal venous arch drains most of the blood from the foot, ultimately carrying the blood to the medially located great saphenous vein or laterally and posteriorly to the small saphenous vein (see Fig. 6-2). The deep fibular nerve, passing from the leg into the foot, innervates the two intrinsic muscles on the dorsum of the foot (see Fig. 6-29).

Muscles, Vessels, and Nerves of the Sole of the Foot

The sole of the foot is protected by a thick layer of the deep fascia called the plantar aponeurosis, which extends from the calcaneal tuberosity to individual bands of fascia that attach to the toes anteriorly (Fig. 6-30).

Beneath the plantar aponeurosis, the intrinsic muscles of the foot are arranged into four layers, shown in sequence in Figures 6-31, 6-32, and 6-33 and Tables 6-20, 6-21, and 6-22. These muscles functionally assist the long muscle tendons that pass from the leg into the foot. The lumbrical muscles and the interosseus muscles have the same actions as their counterparts in the hand. The lumbricals flex the metatarsophalangeal joints and extend the interphalangeal joints via the extensor hood. The plantar interossei adduct (PAD) the digits (2-4) and help flex the metatarsophalangeal joints, while the dorsal interossei abduct (DAB) the digits and help flex the metatarsophalangeal joints. All these intrinsic muscles of the sole are innervated by the medial or lateral plantar nerves (from the tibial nerve) (Tables 6-20, 6-21, and 6-22) and are supplied with blood from the medial and lateral plantar arteries (from the posterior tibial artery). Pulses may be palpated between the medial malleolus and the heel (posterior tibial artery) and on the dorsum of the foot just lateral to the extensor hallucis longus tendon (dorsalis pedis artery).

Clinical Focus 6-34   Plantar Fasciitis

Plantar fasciitis (heel spur syndrome) is the most common cause of heel pain, especially in joggers, and results from inflammation of plantar aponeurosis (fascia) at its point of attachment to the calcaneus. Generally, it is more common in females and obese persons. A bony spur may develop with plantar fasciitis, but the inflammation causes most of the pain, mediated by the medial calcaneal branch of the tibial nerve. Most patients can be managed nonsurgically, but relief from the pain may take 6 to 12 months. Exercises and orthotic devices are usually recommended in the initial course of treatment.

Clinical Focus 6-35   Deformities of the Toes

Clinical Focus 6-36   Fractures of the Talar Neck

The talar neck is the most common site for fractures of this tarsal. Injury usually results from direct trauma or landing on the foot after a fall from a great height. The foot is hyperdorsiflexed so that the neck impinges on the distal tibia. The three types of fractures are as follows:

• Type I: Nondisplaced fractures

• Type II: Neck fracture with subluxation or dislocation of the subtalar joint

• Type III: Neck fracture with dislocation of the subtalar and tibiotalar joints

These fractures can lead to avascular necrosis of the talus body because most of the blood supply to the talus passes through the talar neck.

Clinical Focus 6-37   Common Foot Infections

Clinical Focus 6-38   Diabetic Foot Lesions

Diabetes mellitus (DM), a common complex metabolic disorder characterized by hyperglycemia, affects over 18 million people in the United States. The skin is one of many organ systems affected, especially the skin of the leg and foot. Microvascular disease may result in a decreased cutaneous blood flow. Peripheral sensory neuropathy may render the skin susceptible to injury and may blunt healing. Hyperglycemia predisposes the extremity to bacterial and fungal infection. Associated complications in the lower limb include Charcot joint (progressive destructive arthropathy caused by neuropathy), ulceration, infection, gangrene, and amputation. DM accounts for most nontraumatic foot and lower leg amputations, which total more than 80,000 per year.

Clinical Focus 6-39   Arterial Occlusive Disease

Atherosclerosis can affect not only the coronary and cerebral vasculature but also the arteries that supply the kidneys, intestines, and lower limbs. The resulting arterial stenosis (narrowing) or occlusion in the leg leads to peripheral vascular disease (PVD), a disorder largely associated with increasing age. PVD produces symptoms of claudication, which should be a warning sign of atherosclerosis elsewhere that may produce myocardial infarction and stroke (see also Clinical Focus 6-11).

Clinical Focus 6-40   Gout

Uric acid (ionized urate in plasma) is a by-product of purine metabolism and is largely eliminated from the body by renal secretion and excretion. An abnormally elevated serum urate concentration may lead to gout. Gout is caused by precipitation of sodium urate crystals within the joint's synovial or tenosynovial spaces, which produces inflammation. About 85% to 90% of clinical gout is caused by underexcretion of urate by the kidneys. The disorder may be caused by genetic or renal disease or diseases that affect renal function. Chronic gout presents with deforming arthritis that affects the hands, wrists, feet (especially the great toe), knees, and shoulders.