Knee pain in the right leg is not necessarily cancer, and the cause needs to be clarified by relevant tests. Knee pain may have different causes at different ages. For example, in children, transient synovitis occurs 2-3 days after a cold and usually resolves on its own in about 1 week. Tibial tuberosity epiphysitis can cause pain due to violent movement of the knee, which involves the epiphysis, which in turn causes inflammation and can lead to pain that usually disappears after stopping strenuous exercise. Middle-aged people with unexplained knee pain need to be alert for the presence of gouty arthritis. In addition, cancer can also cause joint pain, usually due to tumor invasion of joints or bones, manifesting as resting pain, with significant pain at night, accompanied by weight loss, loss of appetite and other systemic symptoms. Patients with knee pain should consult a doctor in time to get a clear diagnosis and give appropriate treatment, and also pay attention to rest, avoid walking for a long time, such as climbing stairs and mountains, and wear knee pads for protection.