Medial knee pain may be caused by lesions of the knee joint itself, radiating pain from lumbar spine lesions, and localized lesions. 1. The knee joint itself: muscle strain, knee osteoarthritis, medial collateral ligament injury, meniscus injury, joint inflammation, chondromalacia patella, and bursitis. 2. Radiation pain from lumbar spine lesions: there are lumbar spine 3-4 nerve roots in the medial part of the knee joint, and when the intervertebral disc herniation occurs, the compression of the corresponding nerves may lead to pain. 3. Local lesions: when the tumor occurs near the knee joint, it may compress the knee joint nerve and cause pain in the medial side of the knee joint. In addition, necrosis of the femoral head may also produce entrapment pain and cause knee pain. It is recommended to avoid strenuous exercise, pay attention to rest, and go to the relevant professional department for targeted treatment when knee pain occurs.