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From the University of Pittsburgh, Pittsburgh, Pennsylvania
* Address correspondence to Timothy C. Sell, PhD, PT, Neuromuscular Research Laboratory, UPMC Center for Sports Medicine, 3200 South Water Street, Pittsburgh, PA 15203 (e-mail: tcs15{at}pitt.edu).
Background: Functional adaptations of patients with posterior cruciate ligament deficiency (grade II) are largely unknown despite increased recognition of this injury.
Hypothesis: Posterior cruciate ligamentdeficient subjects (grade II, 6- to 10-mm bilateral difference in posterior translation) will present with neuromuscular and biomechanical adaptations to overcome significant mechanical instability during gait and drop-landing tasks.
Study Design: Controlled laboratory study.
Methods: Bilateral comparisons were made among 10 posterior cruciate ligamentdeficient subjects using radiographic, instrumented laxity, and range of motion examinations. Biomechanical and neuromuscular characteristics of the involved limb of the posterior cruciate ligamentdeficient subjects were compared to their uninvolved limb and to 10 matched control subjects performing gait and drop-landing tasks.
Results: Radiographic (15.3 ± 2.9 to 5.6 ± 3.7 mm; P = .008) and instrumented laxity (6.3 ± 2.0 to 1.4 ± 0.5 mm; P < .001) examinations demonstrated significantly greater posterior displacement of the involved knee within the posterior cruciate ligamentdeficient group. The posterior cruciate ligamentdeficient group had a significantly decreased maximum knee valgus moment and greater vertical ground reaction force at midstance during gait compared to the control group. During vertical landings, the posterior cruciate ligamentdeficient group demonstrated a significantly decreased vertical ground reaction force loading rate. All other analyses reported no significant differences within or between groups.
Conclusion: Posterior cruciate ligamentdeficient subjects demonstrate minimal biomechanical and neuromuscular differences despite significant clinical laxity.
Clinical Relevance: The findings of this study indicate that individuals with grade II posterior cruciate ligament injuries are able to perform gait and drop-landing activities similar to a control group without surgical intervention.
Key Words: posterior cruciate ligament (PCL) knee injuries biomechanics neuromuscular
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