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Factors explaining chronic knee extensor strength deficits after ACL reconstruction
Author(s) -
Krishnan Chandramouli,
Williams Glenn N.
Publication year - 2011
Publication title -
journal of orthopaedic research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.041
H-Index - 155
eISSN - 1554-527X
pISSN - 0736-0266
DOI - 10.1002/jor.21316
Subject(s) - medicine , weakness , physical medicine and rehabilitation , anterior cruciate ligament , muscle weakness , muscle strength , peripheral , knee flexion , physical therapy , anatomy
Persistent quadriceps muscle weakness is common after anterior cruciate ligament (ACL) reconstruction. The mechanisms underlying these chronic strength deficits are not clear. This study examined quadriceps strength in people 2–15 years post‐ACL reconstruction and tested the hypothesis that chronic quadriceps weakness is related to levels of voluntary quadriceps muscle activation, antagonistic hamstrings moment, and peripheral changes in muscle. Knee extensor strength and activation were evaluated in 15 ACL reconstructed and 15 matched uninjured control subjects using an interpolated triplet technique. Electrically evoked contractile properties were used to evaluate peripheral adaptations in the quadriceps muscle. Antagonistic hamstrings moments were predicted using a practical mathematical model. Knee extensor strength and evoked torque at rest were significantly lower in the reconstructed legs ( p < 0.05). Voluntary activation and antagonistic hamstrings activity were similar across legs and between groups ( p > 0.05). Regression analyses indicated that side‐to‐side differences in evoked torque at rest explained 71% of the knee extensor strength differences by side ( p < 0.001). Voluntary activation and antagonistic hamstrings moment did not contribute significantly ( p > 0.05). Chronic quadriceps weakness in this sample was primarily related to peripheral changes in the quadriceps muscle, not to levels of voluntary activation or antagonistic hamstrings activity. © 2011 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29:633–640, 2011