Scientific Article   |    
A Gender-Related Difference in the Contribution of the Knee Musculature to Sagittal-Plane Shear Stiffness in Subjects with Similar Knee Laxity
Edward M. Wojtys, MD; James A. Ashton-Miller, PhD; Laura J. Huston, MS
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Investigation performed at the Department of Orthopaedic Surgery, MedSport, University of Michigan, Ann Arbor, Michigan

Edward M. Wojtys, MD
Laura J. Huston, MS
Department of Orthopaedic Surgery, MedSport, 24 Frank Lloyd Wright Drive, Ann Arbor, MI 48106. E-mail address for E.M. Wojtys: edwojtys@umich.edu

James A. Ashton-Miller, PhD
Biomechanics Research Laboratory, Department of Mechanical Engineering and Applied Mechanics, Department of Biomedical Engineering, and Institute of Gerontology, University of Michigan, Ann Arbor, MI 48109

The authors did not receive grants or outside funding in support of their research or preparation of this manuscript. They did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.

J Bone Joint Surg Am, 2002 Jan 01;84(1):10-16
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Background: Women’s susceptibility to injuries involving the anterior cruciate ligament remains unexplained. Volitional contraction of the knee musculature is known to increase the resistance of the knee to shear deformation, raising the possibility that muscles play a part in protecting the anterior cruciate ligament during hazardous activities. We therefore tested the hypothesis that a volitional co-contraction of the knee muscles increases the sagittal-plane shear stiffness (or resistance to anterior tibial translation) of the knee more in men than in women.

Methods: Twenty-three volunteers (ten men and thirteen women; mean age, 24.7 ± 5.4 years), all with anterior tibial translation of 6 mm, agreed to participate in the study. Each subject underwent a subjective evaluation of knee function and activity level, an arthrometric measurement of passive anterior tibial translation, and an isokinetic dynamometer strength test at 60°/sec. A dynamic stress test was then performed to measure anterior tibial translation while simultaneously monitoring lower-extremity muscle response.

Results: Maximum co-contraction of the knee musculature significantly decreased mean anterior tibial translation in both men and women (from 7.8 mm to 2.2 mm in men and from 6.5 mm to 3.1 mm in women). The corresponding percentage increase in shear stiffness of the knee was significantly greater (p = 0.003) in men (379%) than in women (212%).

Conclusions: The results suggested that women have a diminished potential for muscular protection of passive structures of the knee in anterior tibial translation.

Clinical Relevance: Maximal muscular protection of the anterior cruciate ligament in women may be less than that in men. This may be one factor explaining why more women than men are apt to sustain injuries to the anterior cruciate ligament.

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    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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