Persons most commonly affected: Young people and adults of both sexes.

Organ or part of body involved: Tendons and joints.

Symptoms and indications: Pain and stiffness aggravated by movement. the tendon may grow thicker and be tender to touch or very painful. Pain may be prominent at night.

Causes and risk factors: Improper activity, lack of conditioning, and poor athletic equipment encourages the development of tendinitis. Nonathletes who suddenly begin long-distance jogging or another athletic activity and athletes who resume strenous sports after a period of inactivity are especially susceptible. In addition, people who wear shoes with run-down heels put needless tension on the Achilles tendon, which joins the two major muscles on the back of the leg to the back of the heel bone. Similarly, women who wear high-heel shoes may have problems with inflamed Achilles tendons because the stress created by the shoes considerably strains the tendons. It may also, however, result from an infection or as a complication of a rheumatic or connective tissue disorder.

Prevention: Care should be taken when engaged in sporting or other physical activities to avoid exposing a tendon or joint to unaccustomed or excessive stress. They should warm up prior to exercise, wearing supports in shoes during physical activity can correct instability when tendinitis does occur.