Vastus Medialis: Anatomical and Functional Considerations and Implications Based Upon Human and Cadaveric Studies
Received 3 March 2005; accepted 30 July 2005.
Abstract
Objective
To provide an electrophysiological and functional description of the vastus medialis (VM) and contrast it to an anatomical description.
Methods
Motor points of all superficial portions of the quadriceps were identified on the dominant side of 8 human subjects and electrically stimulated to achieve a light contraction to trace and measure the orientation of the fibers. Electromyography of the VM was then recorded over 2 motor points during isometric and isokinetic maximum knee extensions. An independent laboratory dissected 39 cadaveric specimens focusing on fiber orientations and distal insertions of the VM.
Results
Results revealed 5 motor points for the quadriceps: 1 point for the vastus lateralis, 1 point for the rectus femoris (RF), and 3 points for the VM. The 3 VM motor points suggest 3 separate groups of fibers: proximal (pf), median (mf), distal (df). Fiber orientations ranged from 45° for VMpfs to 55° for VMdfs. Motor point stimulation and anatomical dissection clearly showed that the VMpfs and VMmfs were inserted on a tendon common to the RF, whereas VMdfs were attached directly to the medial aspect of the patella. Furthermore, the VMpfs were more active (P < .05) than VMdfs during maximum knee extensions.
Conclusion
The anatomy, motor points, and electromyography clearly support an important distinction between the VMpfs and VMdfs. The role of the VMpfs would be one of assisting the RF in knee extension, whereas the VMdfs would track the patella medially without participating in knee extension. Because of these anatomical and functional differences, the VMpfs and VMdfs should be addressed very differently during quadriceps rehabilitation in patellofemoral dysfunctions.
aAdjunct Professor, Département de Kinanthropologie, Université du Québec à Montréal, Montreal, Quebec, Canada; Director of R&D, Laboratoire Orthopédique Médicus, Montreal, Quebec, Canada
bAssistant Professor, Department of Exercise Science, Concordia University Montréal and Centre de Recherche Interdisciplinaire en Réadaptation du Montréal Métropolitain-Site, Constance-Lethbridge Rehabilitation Centre, Montréal, Quebec, Canada
cFull Professor, U.F.R. Sciences et Techniques des Activités Physiques et Sportives, Université Blaise Pascal, Aubière Cedex, France
dMedical Doctor, Service de Rééducation Réadaptation Fonctionnelles, Hôpital Nord, Clermont-Ferrand Cedex 2, France
eMedical Doctor, Service de Rééducation Réadaptation Fonctionnelles, Hôpital Nord, Clermont-Ferrand Cedex 2, France; Associate Researcher, Laboratoire d'Anatomie, Faculté de Médecine, Place Henri Dunant, F-63000 Clermont-Ferrand, France
fChairman of the Laboratory, Laboratoire d'Anatomie, Faculté de Médecine, Place Henri Dunant, F-63000 Clermont-Ferrand, France
gFull Professor, Département de Kinanthropologie, Université du Québec à Montréal, Montreal, Quebec, Canada
Submit requests for reprints to: Jean P. Boucher, PhD, Département de Kinanthropologie, Université du Québec à Montréal, Montreal (Quebec), Canada H3C 3P8.
Sources of support: This study was partially supported by the Natural Sciences and Engineering Research Council of Canada Postgraduate Scholarships Program.
ABSTRACT