Injury and local injection and the risk of foot/ankle osteoarthritis: a case-control study in retired UK male professional footballers.

OBJECTIVE: The objective of this study was to examine whether foot/ankle injury and injection contribute to the risk of foot/ankle OA in retired UK male professional footballers. METHODS: This was a case-control study among retired UK male footballers, in which cases reported General Practitioner-diagnosed foot/ankle OA or forefoot/ankle surgery after retirement, and controls reported neither. Injury was defined as significant foot/ankle injury with pain for most days over 3 months during their career. Injection was defined as injection of corticosteroids or other agents into foot/ankle joints during their career. Adjusted odds ratios (aORs) with 95% confidence interval (CIs) were calculated using logistic regression. Areas Under the Curve (AUCs) and 95% CIs were estimated to examine the contribution of injury and/or injection in the context of other available risk factors. RESULTS: Of 424 footballers studied, 63 had foot/ankle OA and 361 had neither. Cases had similar mean age (63.2 vs 63.0, P = 0.457) and BMI (27.7 vs 27.0, P = 0.240) to those of controls, but more foot/ankle injury (73.3% vs 42.5%, P < 0.001) and injections (75.0% vs 48.4%, P < 0.001), with aORs of 4.23 (95% CI 1.88-9.48) and 2.62 (95% CI 1.19-5.78), respectively. The AUC was 0.69 (95% CI 0.62-0.77) for injury, 0.74 (95% CI 0.66-0.81) for injury and injection, and 0.78 (95% CI 0.70-0.85) for all risk factors. Similar results were observed in footballers with ankle OA only. CONCLUSION: Injury was a major risk factor for foot/ankle OA in retired UK male professional footballers. The role of injection needs cautious interpretation due to potential confounding by indication.