A chronic injury is an injury that develops gradually over time due to overuse of one area of the body. Chronic injuries are different from acute injuries, which happen suddenly, such as when a person falls, receives a blow, or twists a joint. Examples of chronic injuries include shin splints, stress fractures, tennis elbow, and runners knee. Symptoms of a chronic injury due to overuse include pain when you play or exercise, swelling, and a dull ache when you rest. Chronic injuries can result from small issues in the way you perform physical activity, such as overuse of specific bones, muscles, or tendons, inadequate equipment, or poor form. Chronic injuries can be difficult to diagnose and treat, and they may require physical therapy or even surgery, depending on the injury.