Interpreting Quadriceps Strength Thresholds for Patients Following ACL-Reconstruction: A Clinical Commentary

Rehabilitation following Anterior Cruciate Ligament Reconstruction (ACLR) is a complex process involving the restoration of muscular strength, movement patterns, and functional confidence. Clinical thresholds, defined target values tied to successful outcomes, are frequently used to guide rehabilitation and assess patient progress. While these thresholds may promote rehabilitation advancement and the establishment of structured goals, substantial variability exists in their values and how they are developed. Clinical thresholds are typically established by linking an independent variable (e.g., quadriceps strength) to a dichotomized outcome (e.g., return to running, return to sport, patient-reported function cutoff, etc.). Statistical tools like Receiver Operating Characteristic (ROC) curve analyses are used to determine a single strength value that best predicts a successful outcome, based on the sensitivity and specificity of predicting the outcome. Despite this standardized approach, existing thresholds differ significantly due to variations in outcome definitions, cohort characteristics, and strength testing protocols. This clinical commentary aims to (1) describe the methodology used to establish clinical thresholds, (2) discuss statistical considerations for interpreting these thresholds, and (3) examine the implications of variability in quadriceps strength targets for patient following ACLR.

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