Joints have a tough job. They must support weight, provide a great variety of body movements, and are used very frequently. In addition to this normal wear and tear, these structures are sometimes subjected to injury from overuse, infection, an immune system launching a misplaced attack, or degeneration. Here is a look at some common joint problems.

Dislocation

A dislocation (luxation) displaces the articulating bones of a joint and usually results from a fall or other unusual body movement. The joints of the shoulders, knees, elbows, fingers, and jaw are common sites for this type of injury. A dislocation produces an obvious deformity of the joint, some loss of ability to move the articulated bones, localized pain, and swelling.

Sprains

Sprains result from overstretching or tearing the connective tissues, ligaments, and tendons associated with a joint, but they do not dislocate the articular bones. Usually forceful wrenching or twisting sprains the wrist or ankles. For example, excessively inverting an ankle can sprain it as the ligaments on its lateral surface are stretched. Severe injuries may pull these tissues loose from their attachments.

A sprained joint is painful and swollen, restricting movement. Immediate treatment of a sprain is rest; more serious cases require medical attention. However, immobilization of a joint, even for a brief period, causes bone resorption and weakens ligaments. Consequently, exercise may help strengthen the joint.

Bursitis

Excessive use of a joint or stress on a bursa may cause bursitis, an inflammation of a bursa. The bursa between the heel bone (calcaneus) and the Achilles tendon may become inflamed as a result of a sudden increase in physical activity involving use of the feet. Similarly, a form of bursitis called tennis elbow affects the bursa between the olecranon process and the skin. Bursitis is treated with rest. Medical attention may be necessary.

Arthritis

Arthritis is a disease condition that causes inflamed, swollen, and painful joints. There are more than a hundred different types of arthritis, affecting 50 million people in the United States. Arthritis can also be part of other syndromes. The most common causes of arthritis are discussed below.

Rheumatoid Arthritis (RA)

This autoimmune disorder (a condition in which the immune system attacks the body's healthy tissues) is the most painful and debilitating form of arthritis. The synovial membrane of a joint becomes inflamed and thickens, forming a mass called a pannus. Then, the articular cartilage becomes damaged, and fibrous tissue infiltrates it, interfering with joint movements. In time, the joint may ossify so that the articulating bones fuse (bony ankylosis). Joints severely damaged by RA may be surgically replaced.

RA may affect many joints or only a few. It is usually a systemic illness, accompanied by fatigue, muscular atrophy, anemia, and osteoporosis, as well as changes in the skin, eyes, lungs, blood vessels, and heart. RA usually affects adults, but there is a juvenile form.

Osteoarthritis

This degenerative disorder is the most common type of arthritis. It usually occurs with aging, but an inherited form may manifest itself as early as one's thirties. A person may first become aware of osteoarthritis when a blow to the affected joint produces pain that is much more intense than normal. Gradually, the area of the affected joint deforms. For example, arthritic fingers take on a gnarled appearance, or a knee may bulge.

In osteoarthritis, articular cartilage softens and disintegrates gradually, roughening the articular surfaces. Joints become painful, with restricted movement. For example, arthritic fingers may lock into place while a person is playing the guitar or tying a shoelace. Osteoarthritis most often affects joints that are used the most over a lifetime, such as those of the fingers, hips, knees, and the lower parts of the vertebral column.

Fortunately, nonsteroidal anti-inflammatory drugs can usually control osteoarthritis symptoms. Exercise can keep stiff joints more flexible, and such simple measures as wearing gloves in the winter can alleviate symptoms.

Gout

Gout is an inborn error of metabolism, an inherited illness in which a defective or missing enzyme causes the chemical it normally acts on to build up. In gout, uric acid crystals accumulate in joints, most commonly the metatarsophalangeal (large toe) joint. Gout was once thought to be caused by eating too much rich food. In a condition called pseudogout, a different type of crystal accumulates, usually in a knee or wrist joint.

Lyme Arthritis

Lyme disease is a bacterial infection passed in a tick bite that causes intermittent arthritis of several joints, usually weeks after the initial symptoms of rash, fatigue, and flu-like aches and pains. Lyme arthritis was first observed in Lyme, Connecticut, where an astute woman kept a journal after noticing that many of her young neighbors had what appeared to be the very rare juvenile form of rheumatoid arthritis. Her observations led Allen Steere, a Yale University rheumatologist, to trace the illness to a tick-borne bacterial infection. Antibiotic treatment beginning as soon as the early symptoms of Lyme disease are recognized can prevent development of the associated arthritis.

Other types of bacteria can cause arthritis too. These include common Staphylococcus and Streptococcus species, Neisseria gonorrhoeae (which causes the sexually transmitted disease gonorrhea), and Mycobacterium (which causes tuberculosis). Arthritis may also be associated with AIDS, because the immunity breakdown raises the risk of infection by bacteria that can cause arthritis.

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