Fig. 3.

Architecture of the multilayered quadriceps tendon. The distal aspect of a right thigh a with corresponding distal section of the quadriceps tendon b is shown. a The architecture of the quadriceps tendon consisting of the rectus femoris (R), vastus lateralis (VL), tensor vastus intermedius (TVI), vastus intermedius (VI) is shown. The medial part of the VI aponeurosis separates into a superficial and deep medial layer. Sartorius (S), patella (P). The insertions of the vastus medialis (VM) into the patella and capsule of the knee joint (blue arrow), rectus femoris (red arrow) and vastus intermedius (green arrow) is marked. Anterior insertion of the vastus medialis in the the vastus intermedius (VM ant), posterior insertion of the vastus medialis into the vastus intermedius (VM post). b The proximal two blue dots (F1 and F2) mark the fusing points of the intermediate layer of the quadriceps tendon. All portions of the extensor apparatus fuse over a region ranging from 13 to 90 mm proximal to the superior pole of the patella (distal blue dot). Lateral portions of the vastus intermedius (lateral VI) form the deepest layer of the quadriceps tendon. The superficial and deep layer of the medial vastus intermedius aponeurosis (black dotted arrows) fuse 56 mm (range, 30 to 90 mm) and 33 cm (range, 13 to 53 mm) proximal to the patella with the aponeurosis of the tensor vastus intermedius (TVI) and vastus lateralis (VL) respectively. Together they built the two-layered intermediate layer of the quadriceps tendon. The tendon of the rectus femoris (R) forms the superficial layer of the quadriceps tendon. For better visualization the fusing point are underlined with black paper. The vastus medialis is released from its insertion into the vastus intermedius and rectus femoris. Depending on the level of virtual transection one finds two, three or four layers (white arrows with numbers). An oblique transection could lead to the impression of a complex multi-layered arrangement of the quadriceps tendon