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Scientific Articles   |    
Articularis Genus: An Anatomic and MRI Study in Cadavers
Stephanie J. Woodley, BPhty, MSc, PhD1; Christopher P. Latimer, BPhty, MSc2; Grant R. Meikle, MBChB, FRANZCR3; Mark D. Stringer, MS, FRCP(UK), FRCS(Engl)1
1 Department of Anatomy, Otago School of Medical Sciences, University of Otago, P.O. Box 913, Dunedin 9054, New Zealand. E-mail address for S. Woodley: stephanie.woodley@anatomy.otago.ac.nz
2 Rangiora Physiotherapy, 215 King Street, Rangiora 7400, New Zealand
3 Department of Radiology, Southern District Health Board, Private Bag 1921, Dunedin 9054, New Zealand
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Investigation performed at the University of Otago, Dunedin, New Zealand



Disclosure: None of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of any aspect of this work. One or more of the authors, or his or her institution, has had a financial relationship, in the thirty-six months prior to submission of this work, with an entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. No author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.

Copyright © 2012 by The Journal of Bone and Joint Surgery, Inc.
J Bone Joint Surg Am, 2012 Jan 04;94(1):59-67. doi: 10.2106/JBJS.K.00157
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Abstract

Background: 

The articularis genus muscle is closely associated with the anterior aspect of the knee joint and may act to elevate or retract the suprapatellar bursa. Its form and function are poorly understood. The purpose of this study was to define the morphology of the articularis genus and its relationship to the suprapatellar bursa.

Methods: 

The articularis genus muscle was investigated in twenty-two human lower limbs obtained from eleven donors (six men and five women; mean age at death, eighty-three years). Eighteen of these limbs underwent magnetic resonance imaging (MRI) followed by dissection. The number, length, physiological cross-sectional area, attachment sites, and orientation of individual fascicles, muscle bundles, and whole muscles were recorded. The remaining four limbs underwent immunohistochemical analysis to determine muscle fiber types.

Results: 

The articularis genus comprised multiple layered muscle bundles originating from the anterior, anterolateral, and/or anteromedial surfaces of the distal third of the femur. Distal attachment sites included the proximal and/or posterior wall of the suprapatellar bursa, the deep surface of the distal tendon of the vastus intermedius, and the medial and lateral aspects of the knee joint capsule. On dissection, the muscle was observed to consist of a mean of seven muscle bundles (range, four to ten), but only a mean of four bundles were observed on MRI scans (p < 0.0001). The mean cross-sectional area of the articularis genus (and standard deviation) was 1.5 ± 0.7 cm2, and its mean fascicular length and bundle physiological cross-sectional area were 5.9 ± 1.0 cm and 0.2 ± 0.1 cm2, respectively. The articularis genus displayed a mixed fiber type, with the proportion of type-I fibers varying among specimens (range, 39.9% to 76.4%).

Conclusions: 

These findings highlight the complex and variable anatomy of the articularis genus, particularly with respect to the number of bundles and the distal attachment sites. Distinguishing the superficial bundles of the articularis genus from the vastus intermedius on MRI can be difficult.

Clinical Relevance: 

Given its relationship to the anterior aspect of the knee joint and its association with the suprapatellar bursa, the articularis genus may be a neglected cause of undifferentiated anterior knee pain.

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    Accreditation Statement
    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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