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The American Journal of Sports Medicine

Year: 2009  |  Volume: 37  |  Issue: 9  |  Page No.: 1743 - 1749

Differences in Sonographic Characteristics of the Vastus Medialis Obliquus Between Patients With Patellofemoral Pain Syndrome and Healthy Adults

M. H Jan, D. H Lin, J. J Lin, C. H. J Lin, C. K Cheng and Y. F. Lin



There is controversy regarding the relationship between patellofemoral pain syndrome (PFPS) and insufficiency of the vastus medialis obliquus (VMO). The conventional clinical practice of VMO strengthening for PFPS has been challenged for lack of evidence. The purpose of this study was to observe the difference in sonographic findings of the VMO between patients with PFPS and healthy adults.


The morphological characteristics of the VMO are different between patients with PFPS and healthy adults.

Study Design

Case-control study; Level of evidence, 3.


Fifty-four patients with PFPS and 54 age-, gender-, body height–, and body weight–matched healthy adults as controls were enrolled in the study to measure by sonography the insertion level, fiber angle, and volume of the VMO at its insertional portion to detect differences between patients with PFPS and healthy controls.


The insertion level, fiber angle, and VMO volume were all significantly smaller in the PFPS group than in the control group (P < .05). Multivariate analysis of variance has revealed a Wilks value of .845 and an F value of 5.640 (P = .001).


There was a significant difference in the 3 VMO measures between patients with PFPS and the healthy controls. Individuals might be predisposed to PFPS by different VMO characteristics, including insertion level and fiber angle. The current study cannot determine whether the observed morphological differences were the results of atrophy in response to pain or if they represent dysplasia that was predisposed to pain development. The clinical manifestations of VMO characteristics should be thoroughly investigated in other populations.

Clinical Relevance: The function of the VMO is important to consider in the rehabilitation of patients with PFPS.

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