Strength-related parameters as predictors of non-contact anterior cruciate ligament injury and re-injury: a scoping review

This scoping review aims to systematically map and synthesize the literature on strength-related and force-producing parameters that have been investigated as predictors or risk factors for primary and secondary (re-injury) non-contact anterior cruciate ligament (ACL) injuries in athletes and non-athletes. The review will identify which lower-extremity strength measures such as isokinetic or isometric quadriceps and hamstring strength, hamstring-to-quadriceps strength ratios, hip strength, jump- and hop-derived power measures, and rate of force development have been assessed prior to injury occurrence and how these parameters have been analyzed in relation to subsequent non-contact ACL injury or re-injury. By collating definitions, measurement protocols, and analytical approaches, the review seeks to: 1. Provide conceptual and methodological clarity regarding strength-related predictors in ACL injury research. 2. Clearly distinguish between primary prevention (prediction of first-time ACL injury) and secondary prevention (prediction of re-injury following ACL reconstruction and return to sport). 3. Identify gaps in the current evidence base that must be addressed before strength-based screening tools or prediction models can be implemented in clinical or sports practice. 4. Establish a foundation for future research on potentially more sensitive constructs, such as adaptive force or muscle stability. Primary and secondary prevention contexts will be explicitly differentiated throughout data charting and synthesis to enable context-specific interpretation of findings.