Rotator cuff tendonitis—also known as impingement syndrome—occurs when the tendons in the rotator cuff region of the shoulder joint become inflamed or irritated. This injury typically occurs over time as a result of repetitive motion or trauma—such as the kind associated with certain sports or activities—or from prolonged pressure to the shoulder (e.g., sleeping on the shoulder every night). Those who participate in sports requiring constant overhead arm extension are especially prone to rotator cuff tendonitis, which is why the condition often is referred to as swimmer’s shoulder, pitcher’s shoulder, or tennis shoulder. In some cases, the injury may occur without a discernible cause. Symptoms of rotator cuff tendonitis often worsen over time and may include pain and swelling in the front of the shoulder and the side of the arm, pain during overhead arm motion or when reaching behind the back, presence of a clicking noise when the shoulder is in motion, and shoulder stiffness and weakness. Diagnosis of this condition may involve a physical examination as well as various strength and range of motion tests. In some cases, diagnostic imaging tools such as ultrasound or MRI may be used. Treatment of rotator cuff tendonitis includes rest, application of hot or cold packs, administration of anti-inflammatory medications, steroid injection, and physical therapy to restore range of motion and increase strength. In severe cases, surgery may be recommended.