Analysis of patellar stabilizers muscles and patellar kinematics in anterior knee pain subjects.
BACKGROUND It has been assumed that patellofemoral pain syndrome results from patellar malalignment. The precise role the vastus medialis obliquus plays in mediating the underlying pathologic abnormality is unclear. HYPOTHESIS The morphologic characteristics of the vastus medialis obliquus correlate to patellar malalignment in patients with patellofemoral pain syndrome. STUDY DESIGN Cross-sectional study; Level of evidence, 3. METHODS One hundred twelve patients with patellofemoral pain syndrome were studied. Six sets of computed tomography axial images were assessed in which knee flexion was 0 degrees, 15 degrees, or 30 degrees and the quadriceps muscle either relaxed or contracted. Measurements of serial cross-sectional areas of the vastus medialis obliquus and patellar malalignment were made. Correlation and stepwise regression models between the vastus medialis obliquus variables and patellar malalignment (lateral shift and patellar tilt) were calculated. Statistics were calculated on 4 subgroups depending on patellofemoral malalignment type. RESULTS Significant correlations were found between measures of cross-sectional areas of vastus medialis obliquus and patellar tilt at 0 degrees and 30 degrees of knee flexion. Using a regression model, it was determined that vastus medialis obliquus is predictive of patellar tilt (R(2) = 0.078-0.130). This explanation was most apparent in the subgroup of patients with extreme patellar tilt and lateral shift malalignments (R(2) up to 0.824). CONCLUSION There are significant correlations between vastus medialis obliquus variables and patellar malalignments in extended knees of patients with patellofemoral pain syndrome. CLINICAL RELEVANCE Vastus medialis obliquus muscle function is important to consider in the rehabilitation of patients with patellofemoral pain syndrome, especially those with extreme patellar tilt and lateral shift malalignments.