Knee pain on exertion may be caused by physiological factors such as exposure to cold or bad lifestyle habits. It may also be caused by pathological factors such as knee injuries, degenerative diseases, infections, metabolic diseases and tumors. 1. Physiological factors: When the knee joint is cold or after standing and walking for a long time, the pain in the knee may be triggered by exertion, which can usually be relieved by resting and keeping warm. 2. Knee injuries: when traumatized, ligament, meniscus or bone injuries of the knee joint may be caused, and the exertion will cause obvious pain symptoms, partly accompanied by swelling and activity limitation. 3. Degenerative disease: after degenerative changes in the knee joint, the cartilage of the knee joint is damaged, and the joint space may be narrowed, which will cause knee pain when you exert yourself to move the knee joint. 4. Infection: when the knee joint is infected with bacteria, it will trigger an inflammatory reaction, resulting in tissue congestion and edema, limitation of activities, and pain when the knee joint is exerted. 5. Metabolic diseases: the more common gout, due to abnormal purine metabolism in the body, uric acid deposition will lead to non-specific inflammation of the knee joint, and will cause pain when exertion. 6. Tumor: a relatively rare factor, when the knee joint bone tumors, due to tumor compression or destruction of bone, exertion will also trigger pain, part of the knee joint will be enlarged, deformity and so on. There may also be synovitis, chondromalacia patella and other diseases when the knee is exerted, so you should consult the doctor in time to find out the reason and avoid delaying the condition.