Equivalent Knee Injury and Osteoarthritis Outcome Scores 12 and 24 Months after Anterior Cruciate Ligament Reconstruction: Results from the Swedish National Knee Ligament Register

Background:It is not clear whether Knee injury and Osteoarthritis Outcome Score (KOOS) results will be different 1 or 2 years after anterior cruciate ligament (ACL) reconstruction.Purpose:To investigate within individual patients enrolled in the Swedish National Knee Ligament Register whether there is equivalence between KOOS at 1 and 2 years after primary ACL reconstruction.Study Design:Cohort study; Level of evidence, 2.Methods:This cohort study was based on data from the Swedish National Knee Ligament Register during the period January 1, 2005, through December 31, 2013. The longitudinal KOOS values for each individual at the 1- and 2-year follow-up evaluations were assessed through the two one-sided test (TOST) procedure with an acceptance criterion of 4. Subset analysis was performed with patients classified by sex, age, graft type, and type of injury (meniscal and/or cartilage injury).Results:A total of 23,952 patients were eligible for analysis after exclusion criteria were applied (10,116 women, 4...