Knee pain after swimming may be caused by physiological factors such as too long swimming time and too cold water temperature, or it may be caused by pathological reasons such as degeneration of the knee joint and gout. 1. Physiological factors: Swimming for too long may lead to fatigue of the soft tissues around the joints, resulting in the accumulation of lactic acid and the symptoms of knee pain; the water temperature is too cold during swimming may lead to spasm of the soft tissues around the joints, which may also lead to the above symptoms. 2. Pathological reasons: due to ageing and long-term repeated wear and tear of knee joints, degenerative diseases may occur, resulting in the formation of bone cumbersome joints, synovial membrane hyperplasia, resulting in increased impact or friction in the joints during swimming, which may also lead to symptoms of knee pain after swimming; patients with gout may experience accumulation of gout in the knee joints, which may also lead to the symptoms mentioned above. There may also be other causes of knee pain after swimming, it is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, and then give targeted treatment or treatment under the guidance of the doctor.