Diagram illustrating tendonitis and tendon rupture Symptoms can vary from aches or pains and local joint stiffness, to a burning that surrounds the whole joint around the inflamed tendon. Learn how repetitive stress injuries cause tendonitis, the common symptoms, and treatment options to ease pain and restore function. Video: What is tendonitis? This animation explains what tendonitis is and what causes it. Tendinitis (also called tendonitis) is a condition that occurs when a tendon — the tough cord that connects muscle to bone — becomes inflamed or irritated. It’s commonly caused by repetitive motion or overuse and often affects areas such as the shoulders, elbows, wrists, knees, and heels. Tendinitis is new or sudden swelling and irritation, called inflammation, of a tendon. Tendons are thick fibrous cords that attach muscle to bone. Tendinitis causes pain and tenderness just outside a joint. Tendinitis can happen in any tendon. It's common around shoulders, elbows, wrists, hips, knees and heels. Tendonitis is an inflammation of a tendon—the tough cord of tissue that connects muscles to bones. Tendonitis can affect any tendon, but is most commonly seen in the wrist and fingers. Tendonitis (tendinitis) is a condition where the connective tissues between your muscles and bones (tendons) inflame. Often caused by repetitive activities, tendonitis can be painful. Tendinitis is inflammation of the tendons, which are the tapered ends of muscles that attach to bones. Tendons are in action every time muscles contract and bones move. As such, tendonitis is often the result of overuse, such as repetitive movements at work. Often, a physical exam alone can diagnose tendinitis. Your healthcare professional may press on the affected joint and move the joint into different positions. Sometimes your healthcare professional may use imaging tests to help with diagnosis. Imaging tests may include: X-rays. Shoulder tendonitis (tendonitis) is inflammation that affects an area within your shoulder joint. Your shoulder joint is kept stable by a group of muscles called the rotator cuff, as well as the biceps tendon.