To determine the efficacy, safety and dose dependency of intra-articular Orthovisc ® hyaluronic acid injections in the ankle.A prospective single blinded study in patients with symptomatic ankle–osteoarthritis. Patients were randomly allocated to 1, 2, 3ml, or 3 weekly injections of 1ml (3× 1ml). Primary outcome was ‘pain during walking’ at 15 weeks measured on a 100mm VAS.Twenty-six patients (ITT) participated. The 3× 1ml dose group showed statistically significant decreases at week 7 for ‘pain during walking’ and ‘pain at rest’ (p=0.046). At week 15 decreases were significant for ‘pain at rest’ (p=0.046). There was no significant decrease of VAS-scores in any of the single dose groups. Seven patients experienced temporary local swelling and increased pain in the injected ankle.Orthovisc ® viscosupplementation in the ankle joint is effective and well tolerated. The 3× 1ml dose regimen shows the best results.