20-year-old patients with painful knee symptoms, commonly due to knee trauma, knee cold or strain, as follows: First, knee trauma: in the process of strenuous exercise, knee injury can occur, the patient will show knee pain, limited movement, and accompanied by knee joint effusion, swelling, X-ray can be found fractures, dislocation, MRI can be found meniscal injury, cartilage injury, the MRI can reveal meniscal damage, cartilage damage, medial and lateral collateral ligament damage, and cruciate ligament damage. Second, cold or strain on the knee joint: Patients with cold or overworked knee joints can suffer from strain on the knee joint, which can also induce knee pain symptoms, knee joint weakness, and decreased knee skin temperature. After hot compresses, physical therapy, massage and rest, the knee pain symptoms can be gradually relieved or even disappear completely. Therefore, if a 20-year-old patient has knee pain, the cause should be clearly identified first, and a complete cure can be obtained with active treatment.