Participants at three months post-operative anterior cruciate, ligament reconstruction (ACL-R) demonstrate differences in lower extremity energy absorption contribution and quadriceps strength compared to healthy controls

Background: The purpose of this study was to compare hip and knee energy absorption contribution (EAC) during a double limb squat (DLS) and quadriceps strength in patients three months post-operative ACL-R versus matched healthy controls. Methods: Twenty-four ACL-R participants (Age = 15.5 +/- 1.3 yrs; Ht = 1.66 +/- .07 m; Mass = 66.3 +/- 15.5 kg) were compared to 24 age, sex, limb, and activity-matched healthy controls (Age = 15.5 +/- 1.2 yrs; Ht = 1.65 +/- .08 m; Mass = 59.0 +/- 9.8 kg). Lower extremity biomechanical data was collected at three months post-operative ACL-R during five consecutive DLS. EAC was calculated during DLS descent. lsokinetic quadriceps strength was collected at 60 degrees/s. Normalized quadriceps peak torque (QUADS) was averaged across five trials. Independent t-tests examined differences in group hip and knee EAC during each task. Separate Pearson product-moment correlations examined the relationship between QUADS and hip and knee EAC during the DLS. Results: ACL-R demonstrated greater injured limb hip EAC (46.4 +/- 16.0) than Healthy (31.7 +/- 11.0) during a DLS (p = 0.001). ACL-R demonstrated less injured limb knee EAC (42.7 +/- 14.6) than Healthy (60.6 +/- 8.9) during DLS (p < 0.001). No differences were seen between uninjured limb hip (ACL-R = 0.0 14.2; Healthy = 33.4 +/- 9.1, p = 0.629) or knee (ACL-R = 56.9 +/- 15.6; Healthy = 59.1 +/- 9.8, p = 0.561) EAC and matched limbs. ACL-R injured limb QUADS was decreased compared to Healthy (ACL-R = 1.1 0.5; Healthy = 2.0 0.5, p < 0.001). No differences were seen in QUADS on the uninjured and matched limbs (ACL-R = 2.0 0.6; Healthy = 1.9 0.5, p = 0.894). There was a weak, negative correlation between injured limb QUADS and hip EAC (r = -0.471, p = 0.001) and moderate, positive correlation between injured limb QUADS and knee EAC (r = 0.615, p < 0.001). Conclusions: ACL-R participants demonstrate different eccentric loading strategies during a DLS at three months postoperative compared to matched healthy controls. (C) 2018 Elsevier B.V. All rights reserved.