Method: Sitting with the knee straight and tense, toes pointing upward, for five seconds once, twenty times as a group, one group in the morning and one in the afternoon. For patients with muscle atrophy and weakness in knee extension, as well as in the early postoperative period (during postoperative bed rest), place a pillow across the knee joint in bed, bend the knee about 30 degrees, and practice straightening the knee joint for five seconds at a time, gradually increasing the number of exercises. This helps the patient to get up and walk again. Purpose: To strengthen the quadriceps muscle strength. For patients with osteoarthritis of the knee, anterior cruciate ligament injury, meniscal injury, post hip replacement, post artificial knee replacement and post femoral surgery.