Anterior cruciate ligament injury alters preinjury lower extremity biomechanics in the injured and uninjured leg: the JUMP-ACL study.
Goerger BM, Marshall SW, Beutler AI, Blackburn JT, Wilckens JH, and Padua DA. Br J Sports Med. Epub Ahead of Print. 2014.
Take Home Message: Individuals who sustain an ACL injury develop altered lower extremity biomechanics compared with their biomechanics prior to the injury. These altered biomechanics are similar to movement patterns that may increase the risk of further ACL injury.
Following anterior cruciate ligament (ACL) injury and reconstruction, patients often employ altered biomechanics, which may explain why they are 5 to 15 times more likely suffer a reinjury. Unfortunately, we don’t know if these altered movement patterns existed before the first ACL injury or if they developed after the injury. If we could identify the altered movement patterns that develop after an injury it may help clinicians optimize rehabilitation procedures and correct any biomechanical patterns that could increase the risk of reinjury. Therefore, Goerger and colleagues completed a prospective, repeated measures, case-cohort study to compare lower extremity biomechanics before ACL injury and following ACL reconstruction in both the injured and uninjured leg. Incoming cadets from US service academies were included in this study. Cadets were baseline tested during the summer prior to their first year and monitored prospectively for ACL injuries. At baseline (pre-injury), participants jumped forward from a 30 cm box and landed with both feet but only the dominant leg landed on a force plate. Upon landing participants immediately performed a maximum vertical jump. The authors used an electromagnetic tracking system to capture biomechanical data. Thirty-one participants sustained an ACL injury during their careers at the service academies (0.3 to 2.8 years after baseline testing). Twelve participants sustained the injury in the leg with baseline data. In contrast, the other 19 participants had an injury to the opposite leg and therefore the authors assessed this group for biomechanical changes in the uninjured leg. All 31 injured participants were matched with control participants with regards to gender, cohort year, and service academy. The authors found that all three groups (controls, ACL injured leg, ACL uninjured leg) had similar biomechanics prior to the ACL injury. Participants with an ACL injury and reconstruction – regardless of leg – had increased frontal plane movement (knee valgus and hip adduction angles) compared with before their injury as well as control participants. Only the leg with an ACL injury presented with decreased sagittal plane loading (decreased anterior tibial shear force, knee extension moment, and hip flexion moment) compared with before their injury.
Overall, the current study demonstrates that individuals, who sustain an ACL injury and later undergo reconstruction, develop new altered movement patterns (e.g., increased frontal plane movement). Further, these movement patterns may increase the risk of ACL injury (increased torsional stresses placed on the knee) compared with controls who had consistent movement patterns over time. The data further highlights the need for clinicians to evaluate patient’s biomechanics following an ACL injury and implement appropriate training regimes into their rehabilitation protocols. While these results may appear beneficial, one must also be careful because we don’t know how different surgeries or rehabilitation protocols may influence someone’s biomechanics. Potentially, some rehabilitation programs may help restore a patient’s biomechanics following ACL injury and surgery. Overall, this study suggests we should evaluate patients with an ACL rupture for altered biomechanics and facilitate appropriate retraining to avoid these high-ris patterns..
Questions for Discussion: What biomechanical data, if any, do you collect during your pre-participation screenings? How comfortable are you, as a clinician with analyzing and retraining patients’ lower extremity biomechanics?
Written by: Kyle Harris
Reviewed by: Jeffrey Driban
Goerger, B., Marshall, S., Beutler, A., Blackburn, J., Wilckens, J., & Padua, D. (2014). Anterior cruciate ligament injury alters preinjury lower extremity biomechanics in the injured and uninjured leg: the JUMP-ACL study British Journal of Sports Medicine DOI: 10.1136/bjsports-2013-092982