The Torque-velocity Relationship And Predicting Function Following Aclr

The torque-velocity relationship is an inherent property of skeletal muscle that indicates normal muscle function. The knee extensor torque-velocity relationship is altered in patients recovering from ACL reconstruction (ACLR). PURPOSE: The purpose of this investigation was to determine if the torque-velocity relationships of the knee extensors and flexors assessed at an early time point post-surgery can be used as a prognostic indicator of acceptable subjective knee joint function later in rehabilitation following ACLR. METHODS: A total of 198 participants following primary unilateral ACLR (22.4 ± 2.2 yr, 90 males, 173.4 ± 14.4 cm,77.3 ± 18.4 kg, visit 1: 5.5 ± 1.3 months post-surgery, visit 2: 8.3 ± 1.6 months post-ACLR) completed 8 repetitions of isokinetic knee extension and flexion at 90°/s and 180°/s bilaterally. The maximum peak torque produced at each contraction velocity was used to operationally define the torque-velocity relationship using the two-point method. Binary outcomes for patient acceptable symptom state (PASS) thresholds were used for satisfactory knee extension strength, the International Knee Documentation Committee (IKDC), and the Knee injury and Osteoarthritis Outcome Score (KOOS) Sport subscale. Binomial logistic regressions were conducted with the torque-velocity variables from visit 1 as predictors and PASS status at visit 2 as outcome variables. Age, sex, and time post-surgery were included as model covariates. RESULTS: Models to predict knee extension strength PASS status at visit 2 were significant with knee extension torque-velocity (p < 0.001) and knee flexion torque velocity (p < 0.001) included, but the model including knee extension had the better fit (pseudo R2 = 0.20, OR: 1.05 [95% CI: 1.01, 1.10]). Knee extension torque-velocity predicted exceeding the IKDC PASS threshold (p = 0.03, OR: 1.02 [95% CI: 0.99, 1.05]), but not KOOS Sport PASS threshold (p = 0.31). CONCLUSION: The torque-velocity relationship, measured on average 5.5 months post-ACLR, was predictive knee extensor strength and IKDC PASS status, but not the KOOS Sport. A metric that allows clinicians to predict satisfactory patient outcomes at later time points post-injury may provide useful clinical intervention points.