Knee pain after exercise can be caused by three factors. First, it is due to strain and cold; second, it is due to trauma; third, it is due to degeneration of the knee joint. In particular, the spasm and edema of the ligaments and joint capsule around the knee joint caused by strain and cold can lead to significant knee pain after exercise, especially when combined with cold, which can easily lead to an increase in spasm and pain. Trauma, especially injury to the ligaments and joint capsule, as well as damage to the cartilage or meniscus inside the knee joint, can also cause significant knee pain during exercise. Degeneration, such as osteoarthritis, in the middle-aged and elderly, can lead to significant osteophytes around the knee joint, as well as degeneration, fracture, exfoliation and meniscal degeneration of the internal cartilage. This condition can also cause significant knee pain when exercising.