Tendinitis, also known as tendonitis, is the inflammation or irritation of a tendon, which connects muscles to bones. In the shoulder, tendinitis often affects the rotator cuff tendons. It commonly occurs due to repetitive overhead activities, such as throwing, painting, or repetitive lifting. Tendinitis can cause pain, tenderness, swelling, and limited range of motion in the affected shoulder. Treatment typically involves rest, ice therapy, anti-inflammatory medications, and physical therapy to strengthen the surrounding muscles and improve flexibility. In some cases, corticosteroid injections may be administered to reduce inflammation and relieve pain. Severe or chronic cases of tendinitis may require surgical intervention to repair the damaged tendon.