An arm or a leg fracture is a break in the continuity of the bone, usually caused by trauma. A fracture can result in substantial muscle, nerve, and other soft-tissue damage. The prognosis varies with the extent of disability or deformity, the amount of tissue and vascular damage, the adequacy of reduction and immobilization, and the patient’s age, health, and nutritional status. Children’s bones usually heal rapidly and without deformity; the bones of adults in poor health or those with osteoporosis or impaired circulation may never heal properly.

Most arm and leg fractures result from trauma, such as a fall on an outstretched arm, a skiing or motor vehicle accident, and child, spouse, or elder abuse (shown by multiple or repeated episodes of fractures). However, in a person with a bone-weakening disease, such as osteoporosis, bone tumor, or metabolic disease, a mere cough or sneeze can cause a pathological fracture. Prolonged standing, walking, or running can cause stress fractures of the foot and ankle—usually in nurses, postal workers, soldiers, and joggers.

Possible complications of fractures include arterial damage, nonunion, fat embolism, infection, shock, avascular necrosis, peripheral nerve damage, and compartment syndrome. Severe fractures, especially of the femoral shaft, may cause substantial blood loss and life-threatening hypovolemic shock.

Carpal tunnel syndrome, a form of repetitive stress injury, is the most common nerve entrapment syndrome. It results from compression of the median nerve in the wrist, where it passes through the carpal tunnel.

The median nerve controls motions in the forearm, wrist, and hand, such as turning the wrist toward the body, flexing the index and middle fingers, and many thumb movements. It also supplies sensation to the index, middle, and ring fingers. Compression of this nerve causes loss of movement and sensation in the wrist, hand, and fingers.

Carpal tunnel syndrome usually occurs in women between ages 30 and 60 and may pose a serious occupational health problem. It may also occur in people who move their wrists continuously, such as butchers, computer operators, machine operators, and concert pianists. Any strenuous use of the hands—sustained grasping, twisting, or flexing—aggravates the condition.

Gout—also known as gouty arthritis—is a metabolic disease marked by monosodium urate deposits that cause red, swollen, and acutely painful joints. Gout can affect any joint but mostly affects those in the feet, especially the great toe, ankle, and midfoot.

Primary gout typically occurs in men over age 30 and in postmenopausal women who take diuretics. It follows an intermittent course that may leave patients symptom-free for years between attacks. Secondary gout occurs in older people.

In asymptomatic patients, serum urate levels rise but produce no symptoms. In symptom-producing gout, the first acute attack strikes suddenly and peaks quickly. Although it may involve only one or a few joints, this attack causes extreme pain. Mild, acute attacks usually subside quickly yet tend to recur at irregular intervals. Severe attacks may persist for days or weeks.

Intercritical periods are the symptom-free intervals between attacks. Most patients have a second attack between 6 months and 2 years after the first; in some patients, the second attack is delayed for 5 to 10 years. Delayed attacks, which may be polyarticular, are more common in untreated patients. These attacks tend to last longer and produce more symptoms than initial episodes. A migratory attack strikes various joints and the Achilles tendon sequentially and may be associated with olecranon bursitis.

Secondary gout can be the result of other diseases such as obesity, diabetes mellitus, polycythemia, and sickle cell anemia.

Eventually, chronic polyarticular gout sets in. This final, unremitting stage of the disease (also known as tophaceous gout) is marked by persistent painful polyarthritis. An increased concentration of uric acid leads to urate deposits—called tophi—in cartilage, synovial membranes, tendons, and soft tissue. Tophi form in the fingers, hands, knees, feet, ulnar sides of the forearms, pinna of the ear, and Achilles tendon and, rarely, in such internal organs as the kidneys and myocardium. Renal involvement may adversely affect renal function.

Patients who receive treatment for gout have a good prognosis.

Hallux valgus is a common, painful foot condition that involves lateral deviation of the great toe at the metatarsophalangeal joint. It occurs with medial enlargement of the first metatarsal head and bunion formation (bursa and callus formation at the bony prominence). It’s more common in women.

With congenital hallux valgus, abnormal bony alignment (an increased space between the first and second metatarsal known as metatarsus primus varus) causes bunion formation. With acquired hallux valgus, bony alignment is normal at the outset of the disorder.

Kyphosis is an anteroposterior spinal curve that causes the back to bow, commonly at the thoracic level but sometimes at the thoracolumbar or sacral level. It was once known as “roundback” or “dowager’s hump.” The normal spine has a slightly convex shape, but excessive thoracic kyphosis is abnormal.

Kyphosis occurs in children and adults. Symptomatic adolescent kyphosis affects more girls than boys and is most common between ages 12 and 16.

Disk lesions (Schmorl’s nodes) may develop in this disorder. These small fingers of nuclear material (from the nucleus pulposus) protrude through the cartilage plates and into the spongy bone of the vertebral bodies. If the protrusion destroys the anterior portions of cartilage, bridges of new bone may form at the intervertebral space and cause ankylosis.

Muscular dystrophy is a group of hereditary disorders characterized by progressive symmetrical wasting of skeletal muscles but no neural or sensory defects. Four main types of muscular dystrophy occur: Duchenne’s (pseudohypertrophic) muscular dystrophy, which accounts for 50% of all cases; Becker’s (benign pseudohypertrophic) muscular dystrophy; Landouzy-Dejerine (facioscapulohumeral) dystrophy; and Erb’s (limb-girdle) dystrophy. Duchenne’s and Becker’s muscular dystrophies affect males almost exclusively. The other two types affect both sexes about equally.

Depending on the type, the disorder may affect vital organs and lead to severe disability, even death. Early in the disease, muscle fibers necrotize and regenerate in various states. Over time, regeneration slows and degeneration dominates. Fat and connective tissue replace muscle fibers, causing weakness.

The prognosis varies. Duchenne’s muscular dystrophy typically begins during early childhood and causes death within 10 to 15 years. Patients with Becker’s muscular dystrophy may live into their 40s. Landouzy-Dejerine and Erb’s dystrophies usually don’t shorten life expectancy.