Exclusion criteria
obesity, bone injuries, knee flexion and extension, knee ligament injuries
OBESITY, OSTEOARTHRITIS OF THE KNEE, DEGENERATION
(1) combined with posterior cruciate ligament rupture; (2) combined with tibial and fibular collateral ligament rupture; (3) combined with meniscus tear; (4) bone-patellar tendon-bone reconstruction of ACL and semitendinosus tendon reconstruction of ACL after surgery; (5) 1 month after the operation, the range of knee flexion and extension is still unable to reach 20°~80° or there is a suspicion of positive anterior drawer test; (6) unable to tolerate isokinetic centrifugal training of popliteus muscle; (7) patients with difficulty in reaching 120° of knee flexion angle due to obesity; (8) History of previous knee ligament injuries with a femoral footprint of < 14 mm; (9) comorbidities such as bone injuries, small intercondylar fossa and joint degeneration; and (10) osteoarthritis of the knee X-ray grading up to grade II, III, or IV lesions; (11) The person who does not co-operate and withdraws from the process.