Methotrexate in the Treatment of Advanced Knee Osteoarthritis With Effusion-synovitis

Inclusion Criteria: * Meet the America College of Rheumatology (ACR) criteria for clinical knee OA assessed by a rheumatologist * Knee pain, visual analogue scale (VAS) pain at least 40mm * Kellgren-Lawrence(K-L) grade of 2-4 * Physical examination showed signs of inflammation (at least 2 of the following 4 clinical signs of inflammation: warmth around the joint; tenderness around joint margin; articular cavity effusion; swelling of soft tissue around the knee joint) * MRI evaluated effusion synovitis grade of ≥ 2 * Capable of understanding the study requirements and willing to cooperate with study instructions, and voluntarily sign informed consent Exclusion Criteria: * Inflammatory arthritis (such as gout, reactive arthritis, rheumatoid arthritis, psoriatic arthritis, seronegative spondyloarthropathy), systemic lupus erythematosus * Knee surgery or arthroscopic examinations were performed or planned within one year, Severe valgus knee deformity (angle of genu valgum \> 30°) or previous traumatic history * MRI contraindications * Intra-articular injection, intramuscular injection or oral glucocorticoid were used within the last 4 weeks * Other anti-synovitis agents (such as hydroxychloroquine and sulfasalazine) were applied in the past 3 months * Clinical significant conditions, such as (but not limited to) active malignant tumor, abnormal renal function (assessed by GFR), hepatic abnormalities \[active hepatitis B, hepatitis C, abnormal liver function (ALT is more than t…