Tendinitis is an inflammation or slight tearing of a tendon or tendon group and usually occurs from overuse or constant stress. Tendons are fibrous structures that attach muscle to bone and can be easily damaged, stressed or torn. Pain, swelling, inflammation and irritation are the most common symptoms of tendinitis. Tendinitis in the wrist, elbow, knee and ankle are all very sports related injuries. Tennis Elbow is one of the most common forms of tendinitis.