The term “tendonitis” means inflammation of a tendon. Tendons are tough fibrous cords of tissue that connect muscles to bones. When muscles contract (tighten) the tendon attachment makes the bone the tendon is attached to move in the direction of the contracted muscle. When the muscle relaxes the bone moves back to its original position.

To picture this, imagine tying a rope (“the tendon”) to a piece of wood that is lying on the floor. When you pull on the rope (contract the muscle), the piece of wood moves up into the air. When you let go (muscle relaxation) the piece of wood drops back to the floor.

Most tendons move inside a sheath that is lined with synovial tissue (the same kind of tissue that lines the inside of joints) and which contains a small amount of lubricating fluid that allows the tendon to glide easily.

Since tendons are made of relatively inelastic tissue, they do not stretch. While this property is good for movement, it makes tendons susceptible to injury. Tendonitis can also occur from overuse. When this situation occurs, the synovial lining that encases the tendon becomes inflamed and swollen.

Tendonitis is more common in middle-aged or older people (“weekend warriors”) but also occurs in younger people who perform repetitive motion tasks or who are engaged in athletics. Also, different types of inflammatory arthritis such as ankylosing spondylitis, psoriatic arthritis, Reiter's disease, and rheumatoid arthritis may make people more susceptible to developing tendonitis. Also, certain antibiotics such as fluoroquinolones can also cause tendon inflammation.

Tendonitis is most common at the following area: shoulder (rotator cuff or biceps), elbow (lateral epicondyle, known as “tennis elbow” or medial epicondyle known as “golfer's elbow”), knee (patellar or quadriceps tendons), hip, Achilles, ankles, and wrists. Tenoitis occurring in the hand can lead to a condition called "trigger finger."

Symptoms consist of pain and stiffness as a well as swelling over the affected tendon. Sometimes it is difficult to see the swelling in large joint areas such as the shoulder or hip.

Because significant inflammation is present, pain with pressure over the tendon and movement of the affected area are common symptoms. There may be redness and warmth over the affected area.

The diagnosis of tendonitis is primarily a clinical one that is suspected by taking a careful history and doing an equally thorough examination. Sometimes, in cases where the diagnosis is uncertain, diagnostic tools such as diagnostic ultrasound or magnetic resonance imaging (MRI) may be useful.

Treatment of tendontis is symptomatic. Non-steroidal anti-inflammatory drugs (NSAIDS) can be helpful for alleviating soreness and pain. Resting the affected area along with icing can also be of assistance.

After a short period of rest, gentle stretching and range-of-motion exercises can be started.

When tendonitis does not respond to these conservative measures, more aggressive approaches are needed. Injection of a combination of lidocaine and a long-acting glucocorticoid (“cortisone”) may be very helpful for breaking the attack. The use of injections should be limited to no more than two or three to the affected area within a given year. The reason is that repeated injections of glucocorticoid weaken the tendon and make it more likely to rupture.

(An incidental note is that the Achilles tendon should never be injected with glucocorticoid because of the danger of rupture).

The use of a splint for a few days to rest the injected area is a good idea.

Surgery may be needed in some stubborn cases.

A new procedure called tenodesis is effective for chronic tendonitis in areas such as the elbow or Achilles. With this procedure a needle is used to irritate the tendon and then platelet rich plasma is injected into the area. This stimulates healing and can make chronic tendonitis better and therefore eliminate the need for surgery.