Association between sonographic morphology of vastus medialis obliquus and patellar alignment in patients with patellofemoral pain syndrome.
METHODS
Descriptive, correlational, anatomical laboratory study.


OBJECTIVE
To investigate the association between the morphology of the vastus medialis obliquus (VMO) and patellar alignment in patients with patellofemoral pain syndrome (PFPS).


BACKGROUND
It has long been presumed that PFPS results from patellar malalignment. Strengthening of the VMO has been suggested as an intervention to treat individuals with PFPS, through correction of abnormal patellar tracking. However, the exact role of the VMO in the etiology and treatment of PFPS is not clear.


METHODS
This study included 58 patients with PFPS, of which 31 had bilateral involvement. A total of 89 knees were imaged with a Merchant's view radiograph at 45 degrees of knee flexion to measure patellar alignment consisting of patellar tilt and congruence angles. Those 89 knees were also examined with sonography with the knee in full extension and quadriceps relaxed to measure VMO morphology and additional characteristics such as insertion level, insertion ratio, fiber angle, and volume. The level of association between radiographic and sonographic measurements was explored to determine any relationship between patellar alignment and morphology of the VMO.


RESULTS
The patellar tilt angle was negatively correlated with the VMO insertion level (r = -.58, P<.05), insertion ratio (r= -.52, P<.05), and volume (r = -.45, P<.05). In addition, the patellar congruence angle was negatively correlated with the VMO fibers angle (r = -.23, P<.05).


CONCLUSIONS
This study showed that some aspects of VMO morphology, measured in full knee extension with the quadriceps relaxed, were associated with patellar alignment measured with the knee at 45 degrees of flexion. Whether or not VMO morphology serves as a predictor of patella alignment with the knee extended should be the focus of future investigations.
Lin
Yeong-Fwu
YF
Department of Orthopaedics, West Garden Hospital, Taipei, Taiwan.
Lin
Jiu-Jenq
JJ
Cheng
Cheng-Kung
CK
Lin
Da-Hon
DH
Jan
Mei-Hwa
MH
D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D031222:Patellar Dislocation / Q000503:physiopathology*; D046788:Patellofemoral Pain Syndrome / Q000209:etiology / Q000628:therapy; D052097:Quadriceps Muscle / Q000000981:diagnostic imaging* / Q000502:physiology; D014463:Ultrasonography