INTRODUCTION. Tibial shaft fractures are among the most common lower extremity fractures. Treatment of tibial shaft fractures with intramedullary nailing has become the treatment of choice in adults. However, commonly reported outcomes include knee pain, limitations in activities of daily living and reduction in quality of life (QOL). The literature lacks high-quality studies to document superiority of intramedullary nailing versus other surgical treatment methods. The present study aims to compare the 12-month Knee Injury and Osteoarthritis Outcome Score (KOOS) – sport and recreation activities (sport/rec) after standard intramedullary nailing with external ring fixation for adult patients with isolated tibial shaft fractures. METHODS. This study is a multicentre randomised, prospective clinical trial. A total of 67 patients will be included in the study, and the primary outcome will be the KOOS-sport/rec at 12 months after surgery. CONCLUSIONS. With KOOS-sport/rec as the primary outcome, the findings of the present study are expected to advance our understanding of knee pain, function and QOL, regardless of the treatment option and the outcome of the stud
