The English Knee Self-Efficacy Scale is a valid and reliable measure for knee-specific self-efficacy in individuals with a sport-related knee injury in the past 5 years

Purpose To translate and cross-culturally adapt the Swedish Knee Self-Efficacy Scale (K-SES) into English and evaluate the measurement properties in a sample of individuals with previous knee injury. Methods Translation, cross-cultural adaptation, and evaluation followed the Beaton multi-step process and COSMIN guidelines. Participants ( n = 125) aged 16–60 years with a sport-related intra-articular tibiofemoral or patellofemoral injury within the last 5 years completed the K-SES, Knee Injury and Osteoarthritis Outcome Score, Anterior Cruciate Ligament-Return to Sport After Injury Scale, Tegner Activity Level Scale, and Multi-dimensional Health Locus of Control. Confirmatory factor analysis (CFA) tested a-priori two-factor structure and model fit. Cronbach-alpha, intra-class correlation coefficient (ICC), and absolute reliability (Bland–Altman plots) were calculated. Construct validity was assessed by eight pre-defined hypotheses. A sub-group of participants ( n = 42) completed the K-SES twice to assess intra-rater reliability. Results The cross-cultural adaptation generated an English K-SES with face and content validity. The original two-factor structure was rejected based on CFA and a revised solution informed by Exploratory Factor analysis resulted in an adequate fit. All construct validity hypotheses were confirmed. The K-SES showed good internal consistency [Factor ( F 1: α = 0.96; F 2: α = 0.73)], intra-rater reliability (ICC = 0.92), and no systematic bias between repeated measurements. Conclusion The English K-SES is a valid and reliable measure for knee-specific self-efficacy in individuals who have sustained a sport-related intra-articular knee injury in the previous 5 years. Level of evidence IV.