Variation of the vastus medialis obliquus insertion and its relevance to minimally invasive total knee arthroplasty.

The aim of the study was to assess population variation of the vastus medialis obliquus (VMO) insertion to the patella. Sixty-five magnetic resonance imaging studies and 18 cadaver specimens were studied. The VMO insertion was expressed as a percentage of patellar length. In the magnetic resonance imaging cohort, the mean insertion was 51% (range 13-95); 59% (38 of 65) of individuals had an insertion within 40% to 60%, with 25% (16 of 65) being distal to 60%. In the cadaveric study, mean insertion was 52% (range 26-81). Both groups displayed a Gaussian distribution. Laterality and sex had no effect upon the level of insertion. The VMO has a variable and frequently distal insertion that may preclude a true quadriceps-sparing approach during minimally invasive knee arthroplasty.