Welcome back to Muscle Talk, over the past couple of weeks we have talked about the muscles that make up the lower extremities. We have covered the hamstrings, glutes, lateral rotators, the adductors, and abductors as well as the hip flexors, and extensors. Today we are going to cover the muscles that make up the quadriceps. The quads make up the upper part of the leg and consist of four muscles, hence the name ‘quadriceps’. These muscles include the rectus femoris, vastus lateralis, vastus medialus, and the vastus intermedius. All four muscles have a common insertion.
The rectus femoris is the most superficial muscle of the anterior thigh. It runs straight down the thigh, and is the only muscle that crosses the hip. It originates at the anterior inferior iliac spine, and superior margin acetabulum, and inserts at the patella and tibial tuberosity via patellar ligament. This muscle extends the knee and flexes the thigh at the hip.
The vastus lateralis is the largest head of the group, and forms lateral aspect of thigh. It originates at the greater trochanter and inserts at the patella and tibial tuberosity via the patellar ligament, just like the rectus femoris. The vastus lateralis extends, and stabilizes the knee.
The vastus medialus forms the inferomedial aspect of thigh. It originates at the linea aspera, medial supercondylar line, intertrochanteric line, and inserts at the patella and tibial tuberosity via the patellar ligament, just like the rectus femoris. The vastus medialus extends knee, the inferior fibers stabilize the patella.
The vastus intermedius is obscured by the rectus femoris, and lies between the lateralis and vastus medialus on anterior thigh. It originates at the anterior and lateral surface of proximal femur shaft and inserts at the patella and tibial tuberosity via the patellar ligament, just like the rectus femoris. The vastus intermedius extends the knee.
Another muscle that is enclosed within the upper thigh and is not actually considered a quadriceps muscle is the tensor fascia latae. It is enclosed between fascia layers of the anterolateral aspect of thigh. Functionally associated with the medial rotators and flexors of thigh, it originates at the anterior aspect of iliac crest and anterior superior iliac spine, and inserts at the iliotibial spine.