Vastus Medialis: a Reappraisal of VMO and VML

[Purpose] The morphology and innervation pattern of the vastus medialis (VM) were investigated to determine if there was an anatomical distinction between the oblique (VMO) and longus (VML) parts. [Subjects and Methods] Forty lower limbs were dissected. The innervation pattern was observed in 39 specimens. Muscle length and fibre angles of 14 specimens were recorded. [Results] In 22 specimens there was a distinct separation between the VML and VMO (change in fibre angle, fibrofascial plane, vasculature or nerve branch). The mean fibre angle of VMO was 52°, and the mean VML fibre angle was 5° (relative to the shaft of the femur). Ten limbs (25.6%) had separate innervation to the VML. The separation between VMO and VML was found to be more proximal than expected, with the VMO on average accounting for 70% of the VM, in contrast to the much more distal point of separation reported elsewhere, leading us to raise the possibility that VML and vastus intermedius may have been misidentified in some previous studies. [Conclusions] In conclusion the VML/VMO division (when present) is much more proximal than has been previously reported, and there is no consistent pattern of innervation to the two parts of the muscle.