Ten cadaveric lower limbs from 7 specimens, three paired and four unpaired (5 men and 2 women; mean age at death 78 years) were investigated using macro dissection techniques. The cadaver parts were obtained from the institutional body donation program (http://www.anatomy.uzh.ch/de/koerperspende.html) following the ethical guidelines “On the use of cadavers and parts of cadavers in medical research and for pre-, postgrad and continued education and research with human subjects” by the Academy of Medical Sciences (SAMS). All lower limbs were embalmed in a formalin-based solution. The thighs were examined on the basis of a standardized dissection protocol. Each lower limb was placed supine on the dissection table. The hip joint was approached from the anterior aspect and the tensor fasciae latae muscle mobilized laterally. The femoral nerve and artery were localized via a second ilio-inguinal approach, and traced distally. With the aid of these neurovascular structures, the muscle bellies of the rectus femoris, the vastus lateralis, the tensor vastus intermedius, vastus intermedius, and vastus medialis were identified. For better visualization the rectus femoris and sartorius were transsected in the mid portion and reflected. Each muscle with its aponeurosis was traced from proximal to distal until they merged into the quadriceps tendon. Connections between the different aponeurotic layers of each muscle were studied from origin to insertion (Fig. 1), with special emphasis on corresponding muscle fibers from the medial and lateral elements. The fusing points of each layer were marked. Their distance to the patella and the distances between the fusing points were measured.Fig. 1Overview of the quadriceps muscle group including the newly discovered fifth component, the tensor vastus intermedius. Anterior view to the left thigh is shown. The red stickers mark the medial and lateral femoral condyles and center of the neck of the femur respectively. For better visualization the sartorius and rectus femoris muscle are transected and reflected. The components of the extensor apparatus are arranged like the layers of a husk of a corn (on the left top). Superficial lateral and medial fibers in the proximal aspect of the thigh are piled in deeper inner layers at the level of the quadriceps tendon. The vastus medialis is released from its insertion into the vastus intermedius, rectus femoris and patella