Tendinitis (Tendonitis) is a common condition that involve inflammation of the soft tissue around muscles and bones, most often in the shoulder, elbow, wrist, hip, knee, or ankle. A tendon is a flexible band of fibrous tissue that connects muscles to bones. Tendinitis is inflammation of a tendon. Tendons transmit the pull of the muscle to the bone to cause movement. They are found throughout the body, including the hands, wrists, elbows, shoulders, hips, knees, ankles, and feet. Tendons can be small, like those found in the hand, or large, like the Achilles tendon in the heel.