We identify all patients who had undergone primary total knee arthroplsty(TKA) from April 1, 2015, to March 30, 2016. Patients are grouped by uric acid level. The knee society score(KSS score) and the hospital for special surgery knee score (HSS score) before the surgery and 6 years after the surgery will be collected. Also the clinical data will be collected.

Inclusion Criteria:

• patients who had undergone primary TKA from April 1, 2015, to March 30, 2016

Exclusion Criteria:

• (1) infection, (2) rheumatoid arthritis, (3) ankylosing spondylitis, (4) revision surgery, (5) patients with unicondylar knee replacement, (6) patients who have been diagnosed with gout or previous gouty symptoms, and (7) patients combined with preoperative redness or swelling.

All patients received primary TKA(totla knee arthroplasty) in our hospital.