Overuse injuries are those caused by repetitive microtrauma to the body’s tendons, bones, and joints. Unlike acute injuries—which typically result from a single traumatic event—overuse injuries develop gradually over time. The most common factor leading to overuse injury is training error. Such errors typically involve a significant jump in training volume or intensity (for example, a runner who increases his or her weekly training volume from three short runs to five long ones). Basically, strenuous exercise causes the body’s tissues to break down and rebuild. When these tissues break down faster than they can repair themselves, overuse injuries occur. Some of the most common overuse injuries are tennis elbow (also known as lateral epicondylitis), swimmer’s shoulder (also known as rotator cuff tendinitis and impingement), runner’s knee, jumper’s knee, Achilles tendonitis, and shin splints. Some people may be more prone to overuse injuries due to certain technical or biomechanical factors, including alignment issues, muscle strength and flexibility imbalances, or anatomical issues such as leg-length discrepancy or high foot arches. In some cases, inadequate athletic equipment—such as worn or ill-fitting footwear—may be to blame. Diagnosis of overuse injuries may involve a physical examination as well as use of X-rays, bone scans, or MRIs. Treatment will vary widely depending on the type and severity of the injury and may involve rest, using alternative forms of exercise (for example, doing low-impact activities like swimming or biking in place of running), taking anti-inflammatory medications, icing, and completing a physical therapy program tailored to the patient’s specific needs.