Tendons are cords of fibrous tissue that connect muscles to bones. It is this connection that allows joint movement. When the muscles contract, they pull on the tendons that make the bones move. For tendons to glide, they move within a lubricated sheath of tissue that is lined with synovial tissue. This synovial tissue is the same type of tissue that lines the inside of joints. Tendinitis refers to a condition in which the sheath through which a tendon slides becomes inflamed. This leads to intense pain. The pain is often made worse by use of the affected joint. However, when tendonitis becomes severe, there may be pain at rest.

Since muscles and tendons surround most joints, tendinitis is quite common. The diagnosis of tendonitis is relatively simple for the experienced clinician. In general, the diagnosis is made by history and physical examination. In cases of difficult diagnosis, MRI is useful to confirm the diagnosis.

Some of the most common types of tendinitis are:

Shoulder tendinitis. The most commonly affected shoulder tendons are the rotator cuff and the biceps tendon. The rotator cuff consists of four tendons that sit on top of the upper arm bone. The location of these tendons and the muscles they attach to are what give the shoulder such a wide range of motion. Rotator cuff tendonitis can occur as a result of repetitive activity or degeneration of the tendon. The pain is felt with most movements and is localized to the outside of the shoulder. The biceps tendon allows the arm to flex at the elbow. Biceps tendonitis also occurs due to repetitive activity and pain is felt in the front of the shoulder. Shoulder tendonitis can be successfully treated with anti-inflammatory medications, physical therapy, and sometimes glucocorticoid injections.

Tendonitis in the elbow is usually located well on the outside and is called lateral epicondylitis or tennis elbow. It can also occur along the inner side of the elbow medial epicondylitis. This is called golfer’s elbow. Treatment consists of physical therapy, stretching and strengthening exercises, splints, and injections. Rarely, surgery is required.

Tendinitis in the wrist arises due to repetitive movement. A special type of tendinitis, called Dequervain’s tendinitis, is felt on the outside of the thumb. Tendinitis in these areas is treated with glucocorticoid injections and splinting. Other physical therapy modalities may be helpful. Sometimes surgery is required. Tendonitis in the fingers can cause toe entrapment. This is called “trigger finger.” Trigger finger usually responds to injection but may require surgical intervention.

Tendinitis in the knee can affect the patellar tendon. This is the tendon that connects the patella to the tibia (lower leg bone). Patellar tendonitis usually occurs due to excessive jumping and is actually called “jumper’s knee.” This is treated with rest, anti-inflammatory medications, and physical therapy.

Ankle tendonitis can occur on the outside of the ankle (peroneal tendonitis), on the inside of the ankle (posterior tibial tendonitis), or on the back of the ankle (Achilles tendonitis). Tendonitis that occurs along the outside or inside of the ankle can occur due to trauma or mechanical instability. Another potential cause is an underlying arthritis condition. Achilles tendonitis often occurs as a result of excessive stress and repetitive trauma. The Achilles tendon is the thick cord at the back of the ankle that connects the heel bone to the calf muscle. Treatment consists of rest, heel elevation to relieve strain on the Achilles tendon, and physical therapy. Injection of glucocorticoids should be avoided due to the danger of Achilles tendon rupture. Anti-inflammatory medications may be helpful.

A new treatment approach has made the need for surgery less likely for patients with chronic tendinitis. The procedure is called “percutaneous needle tenotomy.” In this procedure, a small gauge needle is inserted using ultrasound guidance. The needle is used to irritate the tendons, stimulating the inflammatory response. Platelet-rich plasma, obtained from the entire patient, is then injected into the area where the tendons have been irritated. Platelets are cells in the blood that contain multiple growth and healing factors. The end result is the formation of new healthy tendon tissue.