Tendinosis is a chronic condition that affects the tendons, which are the fibrous tissues connecting muscles to bones. It occurs when the tendon becomes degenerated due to overuse, aging, or repetitive stress, leading to pain and stiffness. Unlike tendinitis, which involves inflammation, tendinosis is characterized by the breakdown of collagen fibers in the tendon. Commonly affected areas include the Achilles tendon, patellar tendon, and rotator cuff. Symptoms may include localized pain, swelling, and reduced strength. Treatment often involves rest, physical therapy, and sometimes injections, but it may take time for the tendon to heal and regain its function.