Tendonitis (also known as tendinitis or tenonitis) is a general term used to describe inflammation associated with a tendon. Tendons connect muscles to bone, and inflammation of these rope-like tissues is the most common cause of soft-tissue pain. Tendonitis differs from arthritis, which refers to inflammation of a joint. Common areas for the condition include the shoulder (which involves inflammation at one of the tendons of the rotator cuff), the elbow (“tennis elbow” and “golfer’s elbow”), the wrist, the knee (above and below the kneecap), the back of the ankle (Achilles tendonitis) and the foot.The onset of tendonitis can usually be attributed to overuse of the associated area, but can also occur in areas where calcium deposits have developed.. As we grow older, repetitive motion can injure the tendon where it attaches to the bone, promoting an inflammatory response by the body. This inflammation can cause “pain on motion,” swelling, warmth, tenderness, and redness. This latter symptom is called “erythema” and refers to the dilation of the blood’s capillaries as part of the inflammatory process.