Bidirectional MR results of knee synovitis and knee OA (A), as well as hand synovitis and hand OA (B). MR, mendelian randomization; N_SNPs, number of single nucleotide polymorphisms; OR, odds ratio; CI, confidence interval; IVW, inverse-variance weighted; MR-PRESSO, MR pleiotropy residual sum outlier; RKOA, radiographic knee osteoarthritis; SKOA, symptomatic knee osteoarthritis; RHOA, Radiographic hand osteoarthritis; SHOA, symptomatic hand osteoarthritis.