Structural re-evaluation of the human gluteus maximus.

The gluteus maximus (GM) is a powerful hip joint extensor acting strongly on the femur. However, most anatomical literature describes that the larger superior portion of the GM is inserted into the iliotibial tract rather than the femur, resulting in an apparent discrepancy between its structure and function. To address this, we re-evaluated the GM structure in 25 formalin-fixed Japanese cadavers. We found that the superior three-fourths of the GM formed a strong plate-like distal tendon, which was mostly inserted into the gluteal tuberosity of the femur, with partial adhesions to the iliotibial tract. The remaining inferior portion terminates at a complex involving the lateral femoral intermuscular septum, plate-like distal tendon of the superior portion, and proximal tendon of the vastus lateralis. These findings resolve the functional anatomy discrepancy of the GM: the larger superior portion is primarily inserted into the femur, contributing hip joint movement, while the smaller inferior portion supports this function. Kinesiological data on the GM should be reinterpreted based on this precise anatomy. This will significantly improve our understanding of human GM function.