Each author certifies that he or she has no commercial associations (eg, consultancies, stock ownership, equity interest, patent/licensing arrangements) that might pose a conflict of interest in connection with the submitted article.Purpose: To investigate relationships between quadriceps strength and neural activity, and to establish a clinical threshold of corticospinal excitability able to discriminate between patients with quadriceps strength indicative of satisfactory and unsatisfactory knee function after ACLR. Methods: A total of 29 patients following primary, unilateral ACL-reconstruction (11 female, 23.2 ± 8.1 years of age, 7.3 ± 2.5 months since surgery) participated.Subjective knee function was quantified using the International Knee Documentation Committee (IKDC) subjective evaluation. Peak isokinetic knee extensor torque was assessed at 90°/s. Quadriceps corticospinal excitability was quantified via active motor threshold (AMT, %2-Tesla) using transcranial magnetic stimulation during a 5% maximal voluntary isometric contraction of the quadriceps. Pearson's r correlations were used to assess the relationship between peak knee extensor torque and AMT. Receiver operating characteristic (ROC) curves were used to establish a threshold of (a) mass-normalized peak knee extensor torque to discriminate satisfactory knee function (IKDC ≥ 75.9%), and (b) AMT to discriminate quadriceps strength indicative of satisfactory knee function. Likelihood ratios (LR) and the magnitude of change in pre-post-test probability were calculated for each threshold. Results: Active motor threshold was negatively correlated with mass-normalized peak knee extensor torque (r = −0.503, P = 0.005). Knee extensor torque ≥1.23 Nm/ kg was an excellent discriminator of satisfactory knee function (AUC = 0.890, P = 0.002; (+)LR = 9.56). An AMT ≤50.5% was an excellent discriminator of quadriceps strength indicative of satisfactory knee function following ACLR (AUC = 0.839, P = 0.005; (+)LR = 23.75). Conclusion: Lower corticospinal excitability was associated with lower quadriceps strength. An AMT above 50.5% was found to decrease the probability of having satisfactory knee strength by over 62%.
K E Y W O R D Santerior cruciate ligament, arthrogenic muscle inhibition, muscle function, patient acceptable symptom state, return to play | 717 BODKIN et al.