Study protocol for an observational register-based study on health and risk factors in patients with hip and knee osteoarthritis

INTRODUCTION: Hip and knee osteoarthritis is a leading cause of disability worldwide. Currently, the course of deterioration in pain and physical functioning in individuals with osteoarthritis is difficult to predict. Factors such as socioeconomic status and comorbidity contribute to progression of osteoarthritis, but clear associations have not been established. There is a need for early identification of individuals with slow disease development and a good prognosis, and those that should be recommended for future joint replacement surgery. METHODS AND ANALYSIS: This nationwide register-based study will use data for approximately 75 000 patients who sought and received core treatment for osteoarthritis in primary healthcare, and were registered in the Swedish population-based National Quality Register for Better Management of Patients with Osteoarthritis. These data will be merged with data for replacement surgery, socioeconomic factors, healthcare consumption and comorbidity from the Swedish Hip Arthroplasty Register, the Swedish Knee Arthroplasty Register, Statistics Sweden and the National Board of Health and Welfare, Sweden. The linkage will be performed using personal identity numbers that are unique to all citizens in Sweden. ETHICS AND DISSEMINATION: The study was approved by the Regional Ethical Review Board in Gothenburg, Sweden (dnr 1059–16). The results from this study will be submitted to peer-reviewed journals and reported at suitable national and international meetings. TRIAL REGISTRATION NUMBER: NCT03438630.