Knee pain when straightening the leg can be caused by multiple factors including muscle tightness or imbalances, tendon inflammation, meniscus tears, knee osteoarthritis, and other conditions like Baker’s cyst or ligament injuries. Common reasons include tight hamstring or calf muscles, patellar tendonitis (inflammation of the tendon connecting the kneecap to the shin bone), meniscus tears affecting the knee cartilage, and osteoarthritis causing joint stiffness and swelling. Symptoms can also include stiffness, swelling, clicking sensations, instability, and limited range of motion. Treatment often involves targeted exercises for strengthening and stretching, physical therapy, rest, pain management, and in some cases, surgery if conservative measures fail.
