Patient samples

Between January 2018 and December 2019, 104 patients with PTOA were enrolled at the Affiliated Jianhu Hospital of Nantong University, with an average age of 52.30±9.97 (age range, 43-63 years; 55 males and 49 females) years. The inclusion criteria for patients with PTOA were as follows: i) all patients met the diagnostic criteria of PTOA according to clinical manifestations and imaging results and ii) all patients had at least one injured knee joint (left or right). The Kellgren-Lawrence (KL) scale (grades 0-4) was used to determine the severity: grade 0, no radiographic features of OA are present; grade 1, possible narrowing of the joint space and osteophytic lipping; grade 2, definite osteophyte formation and possible narrowing of the joint space; grade 3, moderate osteophyte formation, definite narrowing of the joint space, some sclerosis and possible bone contour deformity; and grade 4, large osteophytes, marked narrowing of the joint space, severe sclerosis and definite bone contour deformity (15). Only knee OA patients with KL grades of ≥2 were considered to be significant and were subsequently enrolled. If a patient had bilateral knee OA, the more affected knee was defined as the study knee. The X-ray was read by two orthopedic experts in our hospital in a blinded manner. KL scale classification was used to evaluate the imaging severity. The exclusion criteria were as follows: non-traumatic arthritis, rheumatoid arthritis, suppurative arthritis, gout, diabetes or knee mechanical injury. Synovial fluid (SF) was obtained from 106 knees of patients with PTOA at the time of knee arthroscopy or total knee replacement surgery. Human synovium was harvested from the knee joints of patients during total knee arthroplasty. The synovium and synovial tissue from knee joints donated voluntarily by 60 patients undergoing amputations (51.40±10.69 years; age range, 40-63 years; 33 males and 27 females) were obtained during the same period. There was no previous history of joint pain, joint activity restriction or joint swelling, no disease affecting the synthesis or metabolism of bone or joints. Synovitis and articular cartilage degeneration were excluded by the knee joint examination before, during and after surgery. There were no significant differences between the two groups regarding age, sex or other general information. The present study was approved by the Research Ethics Committee of the Affiliated Jianhu Hospital of Nantong University, and all the participants provided written informed consent to participate in this study.