Causal association between hallux valgus and osteoarthritis: a Mendelian randomization study

Background Hallux valgus (HV) is considered to be associated with osteoarthritis (OA). However, the causal relationship between HV and OA remains confounded. Methods In this study, we aimed to examine the causal effect of HV and OA using two-sample Mendelian randomization (MR) analysis, which included MR Egger, weighted median, inverse variance weighting (IVW) and weighted mode method. Results HV was demonstrated as a causal risk factor of total OA by IVW method (OR = 1.008, 95% CI = 1.004–1.012, p  = 1.758 × 10 ^− 3 ). To further confirm the causal association between HV and various types of OA, we performed validation in knee OA and hip OA and showed that HV was the cause of knee OA (OR = 1.347, 95% CI = 1.100-1.649, p  = 0.004), but not hip OA (OR = 1.103, 95% CI = 0.807–1.507, p  = 0.539). Conclusion This study provided robust evidence of a causal relationship between HV and knee OA, indicating that HV should be corrected promptly to reduce the incidence of OA.