Since tendon tissue is attached to the surface of bone for a long time, tendonitis often causes pain and swelling in the area where the bone protrudes when it occurs. Tendonitis is the result of overuse of fibrous tissue outside the tendon due to long-term frequent exercise, which enhances the pull on the tendon, leading to wear and tear or injury to the tendon and surrounding tissues, producing pain, swelling and other sterile inflammatory reactions. It occurs mostly in the joints of the shoulder, knee and ankle. When tendonitis occurs in the body, significant pain is felt in the bony prominences and localized swelling may occur. As the inflammation spreads, it can also lead to stiffness and difficulty moving the joint at the site of injury. Warmth may also be felt as the hematoma around the inflamed area absorbs. When there is redness, swelling and pain at the site of the bone protrusion, it is important to pay attention to it and go to the hospital in a timely manner in order to clarify the cause of the disease.