Inclusion Criteria:  Patients with confirmed primary knee osteoarthritis in stage IV by preoperative X-ray were included in present study. Kellgren-Lawrence Radiology standards for stage IV were listed as follows: obviously narrowed joint space; vast osteophytes are formed; severe osteosclerosis under the cartilage; bone hypertrophy and evident deformity  Exclusion Criteria:  Subsequent arthritis (including rheumatoid arthritis, Gouty arthritis, traumatic arthritis, etc.) were excluded.