Vastus medialis atrophy not associated with patellofemoral pain, maltracking in women
Contrary to commonly cited theory, atrophy of the vastus medialis muscle has no relation to lateral tracking of the patella and nontraumatic patellofemoral pain in women, according to published results.
To determine the effect of isolated vastus medialis atrophy on patellofemoral pain (PFP), researchers at the University of Southern California retrospectively compared anatomical measurements and MRI scans of 52 women with nontraumatic PFP and 64 women without PFP.
According to the study, individual muscle volumes and cross-sectional measurements were obtained for the vastus medialis (VM), vastus lateralis, vastus intermedius and rectus femoris.
After comparing absolute and normalized individual quadriceps muscle volumes between the groups, the researchers found “no significant difference” in absolute total quadriceps volume between the PFP group (1493.9 cm3) and control group (1434.3 cm3). Similarly, they found “no significant difference” in normalized muscle volume between the PFP group (24.7 cm3/kg) and control group (24.1 cm3/kg).
Thus, no correlation between isolated atrophy of the VM, PFP and maltracking in women could be made, the researchers wrote in the study.
“Our findings call into question the role of quadriceps atrophy as a contributor to patellofemoral joint dysfunction,” the researchers wrote. “The information obtained from this study may provide insight into the potential mechanisms underlying patellofemoral joint dysfunction, which in turn may be useful in guiding rehabilitation efforts,” they added.
Perspective
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Patellofemoral (PF) pain is among the most common complaints in orthopedic patients. Underlying causes of PF are understood to be multifactorial – encompassing a number of anatomic parameters that may contribute to the overall positioning of the patella within the trochlea both statically, as well as dynamically. Ho and colleagues’ paper adds to the existing literature that isolated vastus medialis atrophy is not the sole culprit in explaining why patients suffer from this common ailment.
Moreover, this study helps to reinforce our need as treating surgeons to look beyond the VMO when assessing and explaining to patients the cause of their symptoms. A thorough evaluation of individual patients suffering from chronic patellofemoral pain requires evaluation of factors including alignment, gait, ligamentous laxity, torsional profile and presence of trochlear dysplasia, as well as dynamic variables surrounding the gait cycle - encompassing hip and core mechanics to foot and ankle disposition and strength.
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