A newly discovered membrane at the origin of the proximal tendinous complex of the rectus femoris

Purpose The rectus femoris (RF) forms the anterior portion of the quadriceps muscle group. It has a proximal tendinous complex (PTC) which is constituted by a direct tendon (DT), an indirect tendon (IT), and a variable third head. Direct and indirect tendons finally converge into a common tendon (CT). All the PTC shows a medially sloping in its proximal insertion.We investigated several anatomical specimens and discovered a new component: a membrane connecting the CT with the anterior superior iliac spine. Such membrane constitutes a new origin of the PTC. The aim of this study was to clarify whether this membrane was an anatomical variation of the PTC or a constant structure and to describe its morphology and trajectory. Material and methods We dissected 42 cadaveric lower limbs and examined the architecture of the PTC. We paid special attention to the morphology and interaction patterns between the tendons and the membrane. Results We demonstrated that the membrane is a constant component of the PTC. It has a lateral to medial trajectory and is in relation to the common tendon, the DT, and IT, which present a medial slope. This suggests that the membrane has an stabilizer role for the PTC, acting as a corrector of the inclined vector of the complex. Conclusion The RF injuries are frequent in football. The newly discovered membrane is a constant component of the PTC and its integrity should be included in the algorithm to diagnose injuries.