Vastus Medialis Obliquus Muscle Morphology in Primary and Recurrent Lateral Patellar Instability

Figure 1

Measurement of VMO cross-sectional area. The longitudinal axis of the patella and the femoral shaft axis (dashed line) were established in the central sagittal plane (a). In this sagittal image, the corresponding transverse slice located at the proximal patellar pole, indicated by the red line (c), and the adjacent slices located above (b) and below (d) this reference slice were identified. These transverse planes were used to measure the VMO cross-sectional area by manually drawing disarticulation contours around the muscle boundaries (solid lines in (b-c)). Additionally, the transverse reference image (c) was used to determine the corresponding sagittal slice located centrally in the VMO muscle (dotted line in (c)).