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.

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

Related Posts:

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