Abstract
PurposeThe function of the anterior cruciate ligament (ACL) patients’ non-injured leg is relevant in light of the high incidence of secondary ACL injuries on the contralateral side. However, the non-injured leg’s function has only been examined for a selected number of neuromuscular outcomes and often without appropriate control groups. We measured a broad array of neuromuscular functions between legs of ACL patients and compared outcomes to age, sex, and physical activity matched controls.MethodsThirty-two ACL-deficient patients (208 ± 145 days post-injury) and active and less-active controls (N = 20 each) participated in the study. We measured single- and multi-joint neuromuscular function in both legs in each group and expressed the overall neuromuscular function in each leg by calculating a mean z-score across all neuromuscular measures. A group by leg MANOVA and ANOVA were performed to examine group and leg differences for the selected outcomes.ResultsAfter an ACL injury, duration (−4.3 h/week) and level (Tegner activity score of −3.9) of sports activity decreased and was comparable to less-active controls. ACL patients showed bilateral impairments in the star excursion balance test compared to both control groups (P ≤ 0.004) and for central activation ratio compared to active controls (P ≤ 0.002). There were between-leg differences within each group for maximal quadriceps and hamstring strength, voluntary quadriceps activation, star excursion balance test performance, and single-leg hop distance (all P < 0.05), but there were no significant differences in quadriceps force accuracy and variability, knee joint proprioception, and static balance. Overall neuromuscular function (mean z-score) did not differ between groups, but ACL patients’ non-injured leg displayed better neuromuscular function than the injured leg (P < 0.05).ConclusionsExcept for poorer dynamic balance and reduced quadriceps activation, ACL patients had no bilateral neuromuscular deficits despite reductions in physical activity after injury. Therapists can use the non-injured leg as a reference to assess the injured leg’s function for tasks measured in the present study, excluding dynamic balance and quadriceps activation. Rehabilitation after an ACL injury should be mainly focused on the injured leg.Level of evidenceIII.
Highlights
An injury to the anterior cruciate ligament (ACL) compromises the injured but presumably the non-injured limb’s function
For central activation ratio compared to active controls (P ≤ 0.002)
There were between-leg differences within each group for maximal quadriceps and hamstring strength, voluntary quadriceps activation, star excursion balance test performance, and single-leg hop distance, but there were no significant differences in quadriceps force accuracy and variability, knee joint proprioception, and static balance
Summary
An injury to the anterior cruciate ligament (ACL) compromises the injured but presumably the non-injured limb’s function. Knee Surg Sports Traumatol Arthrosc (2017) 25:172–183 the non-injured leg after the first ACL injury is clinically important because 8 % of the ACL reconstructed patients suffer a subsequent ACL injury to the non-injured leg, with an even higher risk for patients younger than 25 years (11 %) [48]. To determine the functional deficit in the non-injured leg after an ACL injury, it would be necessary to compare patient outcomes to an age, sex, and physical activity matched control group. Since the amount of physical activity decreases following the injury ACL patients’ leg function should be more appropriately compared against a less-active control group matched to the ACL patients’ post-injury activity level
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