Defining the minimal clinically important difference for IKDC and KOOS scores for patients undergoing tibial tubercle osteotomy for patellofemoral pain or instability

Purpose The aim of the present study is to define the minimal clinically important difference (MCID) for International Knee Documentation Committee (IKDC) and Knee Injury and Osteoarthritis Outcome Score (KOOS) for patients undergoing tibial tubercle osteotomy (TTO) for either (1) patellofemoral pain or (2) patellar instability. Methods Patients undergoing TTO for either patellofemoral pain or patellar instability by one of two sports medicine fellowship‐trained surgeons at a single institution between September 2014 and May 2023 were included in the study. IKDC and KOOS scores were collected preoperatively and minimum 1 year postoperatively. Distribution‐based methods were used to calculate the MCID. Results Seventy‐seven patients (82 knees) were included, with a median age of 29.3 years (interquartile range [IQR]: 22.2−36.3 years) and a median BMI of 24.5 kg/m2 [IQR: 22.3−28.3 kg/m2]. Fifty‐seven patients (74%) were female, and there were 40 right knees (49%). The median time to IKDC and KOOS score was 1.8 and 1.7 years, respectively. Forty‐five patients (46 knees) underwent TTO for patellofemoral instability, and 32 patients (36 knees) underwent TTO for patellofemoral pain. The MCID was 11.5 for IKDC, 10.2 for KOOS pain, 10.1 for KOOS symptoms, 9.9 for KOOS ADL, 14.2 for KOOS sport and 14.2 for KOOS QoL for patients undergoing TTO for patellofemoral pain. The MCID was 11.2 for IKDC, 10.1 for KOOS pain, 10.6 for KOOS symptoms, 10.2 for KOOS ADL, 16.0 for KOOS sport and 13.2 for KOOS QoL for patients undergoing TTO for patellar instability. Conclusion We define the MCIDs for commonly used patient‐reported outcome measures for patients undergoing TTO for either patellofemoral pain or patellar instability. Level of Evidence Level II.