Tendonitis

What Is It?

Tendonitis is the inflammation, irritation or microscopic tearing of a tendon — a band of tough, flexible, fibrous tissue that connects muscle to bone. Tendons range in size from the delicate, tiny bands of the hands to the heavy, ropelike cords that anchor the calf or thigh muscles. In most cases, tendonitis occurs because of overuse (too many repetitions of a particular body motion) or overload (a sudden increase in activity, with increased demand for muscle performance). Rarely, tendonitis occurs because of an infection, including gonorrhea. Although tendonitis can affect tendons anywhere in the body, the most common sites are the shoulder, elbow, knee, wrist and heel.

Tendonitis in the shoulder — Rotator-cuff tendonitis is the most common form of tendonitis to affect the shoulder joint. It involves the tendon of the supraspinatus muscle, which attaches to the upper portion of the humerus at the shoulder joint. Less commonly, the tendon of the infraspinatus muscle is affected. In most cases, the supraspinatus tendon is injured by overuse, typically in an occupation or sport that requires the arm to be elevated repeatedly. People at risk include carpenters, painters, welders, swimmers, tennis players and baseball players. The average patient is a male laborer older than 40, whose shoulder complaints are on the same side as his dominant hand, for example, right shoulder pain if he is right-handed.

Tendonitis in the elbow — Two forms of tendonitis commonly involve the elbow: lateral epicondylitis and medial epicondylitis. Both are very common overuse injuries among athletes involved in throwing and racquet sports.

Lateral epicondylitis (tennis elbow) causes pain on the outer side of the elbow joint. Lateral epicondylitis probably affects 40 percent to 50 percent of all adult athletes who play racquet sports. It also can be caused by any activity that repeatedly twists and flexes the wrist, such as pulling weeds, using a screwdriver or even carrying a briefcase.

Medial epicondylitis (golfer's elbow) causes pain on the inner side of the elbow. It is a less common injury than tennis elbow and, despite its name, it is more likely to be related to occupation than to sports. When it does occur as a sports injury, medial epicondylitis can be triggered by swinging a golf club or throwing a baseball repeatedly.

Tendonitis in the knee — Jumper's knee, the most common form of knee tendonitis, involves either the patellar tendon at the lower border of the kneecap or the quadriceps tendon at the upper border of the kneecap. It is a common overuse injury, especially in basketball players and long-distance runners.

Tendonitis in the wrist — In the wrist, tendonitis commonly appears in the form of de Quervain's disease, a condition that causes pain in the back of the wrist at the base of the thumb. Although de Quervain's disease usually occurs in people who perform repetitive grasping or pinching motions with the thumb, it sometimes develops spontaneously in pregnant women.