A tendon is thick, fibrous cord that connects a muscle to a bone. Tendonitis is inflammation or irritation of a tendon. The condition, which causes pain and tenderness just outside a joint, is most common around shoulders, elbows, knees and ankles. It also occurs in hips and wrists. The pain can worsen if damage progresses because of continued use of the joint.

What causes tendonitis?

The most common cause of tendonitis is repetitive stress, or using the same joint for the same movement over and over. As a result, tendons, which normally are able to take lots of bending, stretching and twisting, become inflamed and painful. Tendonitis occurs in many sports that use repetitive movements. You often hear tendonitis referred to as jumper’s knee, golfer’s elbow or swimmer’s shoulder, for example. Tendonitis can also result from jobs that require repetitive movements. Construction workers, painters and factory workers are more likely to develop the problem.

The age-related wear and tear on tendons can cause tendonitis, too, as muscles and tendons lose their elasticity.

Some inflammatory diseases, such as rheumatoid arthritis, can lead to tendonitis pain.