Motion Alterations After Anterior Cruciate Ligament Reconstruction: Comparison of the Injured and Uninjured Lower Limbs During a Single-Legged Jump

Context: Asymmetries subsist after anterior cruciate ligament reconstruction (ACL-R), and it is unclear how lower limb motion is altered in the context of a dynamic movement. Objective: To highlight the alterations observed in the injured limb (IL) during the performance of a dynamic movement after ACL-R. Design: Cross-sectional study. Setting: Research laboratory. Patients or Other Participants: A total of 11 men (age = 23.3 +/- 3.8 years, mass = 81.2 +/- 17.0 kg) who underwent ACLR took part in this study 7.3 +/- 1.1 months (range = 6-9 months) after surgery. Intervention(s): Kinematic and kinetic analyses of a single-legged squat jump were performed. The uninjured leg (UL) was used as the control variable. Main Outcome Measure(s): Kinematic and kinetic variables. Results: Jump height was 24% less for the IL than the UL (F-1,F-9 = 23.3, P = .001), whereas the push-off phase duration was similar for both lower limbs (P = .96). Knee-joint extension (F-1,F-9 = 11.4, P = .009), and ankle plantar flexion (F-1,F-9 = 22.6, P = .001) were less at takeoff for the IL than the UL. The hip angle at takeoff was not different between lower limbs (P = .09). We found that total moment was 14% less (F-1,F-9 = 11.1, P = .01) and total power was 35% less (F-1,F-9 = 24.2, P = .001) for the IL than the UL. Maximal hip (P = .09) and knee (P = .21) power was not different between legs. The IL had 34% less maximal ankle power (F-1,F-9 = 11.3, P = .009) and 31% less angular velocity of ankle plantar flexion (F-1,F-9 = 17.8, P = .004) than the UL. Conclusions: At 7.3 months after ACL-R, motion alterations were present in the IL, leading to a decrease in dynamic movement performance. Enhancing the tools for assessing articular and muscular variables during a multijoint movement would help to individualize rehabilitation protocols after ACL-R.