Unilateral ACL Injury Does Not Affect Neuromuscular Function In The Non-injured Leg

Abstract

PURPOSE: Several reports suggest that an ACL injury causes long-lasting neuromuscular changes not only in the injured but also in the non-injured leg. Such changes, however, were examined only for a selected number of neuromuscular measures. Therefore, we compared a broad array of neuromuscular functions between ACL patients’ non-injured leg and the legs of active and less-active healthy controls. METHODS: Thirty-two ACL patients (208 ± 145 days after injury, 23 ± 4 years) and 20 active (22 ± 2 years) and 20 less-active (22 ± 1 years) healthy subjects were included in the study. The design allowed us to control for age, gender, leg dominance, and levels of physical activity for a comparison of variety of neuromuscular functions between the groups using a one-way ANOVA. In addition, the outcome on every measure was converted to a z-score and the mean z-score was calculated for each subject and used to test the overall difference in neuromuscular function between groups. RESULTS: Levels of physical activity, expressed as weekly hours of sport activity, were similar in the ACL patients prior to injury and the active controls (6.9 hours) (p = 0.924) and these levels were also similar between ACL patients following the injury and the less-active controls (2.6 hours) (p = 0.983). Dynamic hamstring strength, measured at 120°/s, was higher for active than less-active controls (p = 0.047, d = 0.72), while dynamic balance, measured with the start-excursion balance test, was worse for ACL patients compared with active (p = 0.021, d = 0.80) and less-active controls (p = 0.014, d = 1.00). None of the other neuromuscular measures, including static single leg balance, single leg hop distance, maximal static and dynamic quadriceps and hamstring strength, quadriceps force accuracy and steadiness, and knee joint proprioception showed between-group differences (all p ≥ 0.173). Also, the overall index of neuromuscular function was not different between ACL patients (z-score: 0.13 ± 0.31), active controls (z-score: 0.04 ± 0.40), and less-active controls (z-score: -0.05 ± 0.50) (p = 0.306). CONCLUSION: Neuromuscular function of the ACL patients’ non-injured leg was not impaired despite the reduction in physical activity following an ACL injury. Therapists should focus on the injured leg in the rehabilitation process following an ACL injury.