Generally, tendonitis refers to inflammation of a tendon, whereas tendinosis refers to tinny tears in the tissue in and around the tendon. A tendon is fibrous band of connective tissue that essentially connects muscle to bone. Tendons tend to be quite resilient and generally extremely tough and are seldom torn, even when an injury is severe enough to break a bone or tear a muscle. Most tendon injuries tend to occur near joints such as the shoulder, elbow, knee and ankle.