2.1. Patients selection

To address the proposed hypothesis, potential subjects who were in accordance with the following criteria were enrolled:

meet American College of Rheumatology (ACR) radiological and clinical criteria for OA of the knee;

age< = 65years old;

Body mass index (BMI) <25kg/m².^[4]

Exclusion criteria:

attacked by gout previously;

had surgery of the detected knee joint previously;

had other rheumatoid conditions;

had trauma of the detected joint previously.

Following these considerations, consecutive patients between June 2015 and July 2017 were recruited in Hainan general hospital. Subjects were informed of and provided written and verbal consent to the experimental protocol and procedures. This study was approved by the Ethics Committee of Hainan general hospital (Ethical approval No.:Med-Eth[2018]78).