Unloading shoes for osteoarthritis of the knee: protocol for the SHARK randomised controlled trial

Background: Knee osteoarthritis (OA) is a common and disabling condition. Abnormalities in knee loading play an important role in disease pathogenesis, yet there are few non-surgical treatments for knee OA capable of reducing knee load. This two-arm randomised controlled trial is investigating the efficacy of specially-designed unloading shoes for the treatment of symptoms in people with knee OA. Methods/Design: 164 people with symptomatic medial tibiofemoral joint OA will be recruited from the community and randomly allocated to receive either unloading shoes or control shoes. Unloading shoes have a specially-designed triple-density midsole where the medial side is softer than normal and the lateral side harder as well as a lateral wedge between the sole and sock-liner. Control shoes are standard athletic shoes and do not contain these features. Participants will be blinded to shoe allocation and will be instructed to wear the shoes as much as possible every day for 6 months, for a minimum of 4 hours per day. The primary outcomes are knee pain (numerical rating scale) and self-reported physical function (Western Ontario and McMaster Universities Osteoarthritis Index) measured at baseline and 6 months. Secondary outcomes include additional measures of knee pain, knee stiffness, participant global ratings of change in symptoms, quality-of-life and physical activity. Conclusions: The findings from this study will help determine whether specially-designed unloading shoes are efficacious in the management of knee OA.