The Quadricep muscles are located on the anterior portion of your thigh. Combined, their function is to flex the hip and extend the leg at the knee joint. The reason it is called the Quadricep is that it is made of four major muscles (Quad-). These muscles include the rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius.
The most superior of all the muscles is the rectus femoris. The word rectus signifies that this muscle is straight. Other muscles that start with rectus include the ocular muscles and the rectus abdominus. The other part of the word rectus femoris signifies that this muscle is mainly used to move the femur. and is found in the anterior compartment of the leg. The origin of this muscle is the anterior inferior iliac spine. From this point, it will move down the femur and attach to the tibial tuberosity and the patella. As well as extending the knee the rectus femoris is responsible for aiding the iliopsoas in hip flexion.
You may have noticed that the other three muscles in the quadricep begin with the same word, vastus. Vastus in anatomy means “great”. The three great muscles are separated based on their location in the leg. The vastus lateralis is the most lateral or most outward muscle, the vastus medialis is the most medial muscle or closest to the inner leg, and finally, the vastus intermedius is located behind the rectus femoris and between the other two vastus muscles.
The vastus lateralis is the largest and most powerful muscle in the quadriceps. It moves down the lateral part of the leg in the anterior compartment. Its origin via a broad area on the upper area of the femur and inserts at the tibial tuberosity via the patellar tendon. This means that the function of these muscles is for leg extension at the knee joint.
The vastus intermedius is located below the rectus femoris and begins at the anterior shaft of the femur. It will move straight down and attach to the tibial tuberosity via the patellar tendon and the patellar via the quadriceps tendon. The function of this muscle is to extend the leg via the knee joint.
The final vastus muscle is the vastus medialis. This muscle is located on the medial portion of your leg and begins at the shaft of the femur. It will move down the medial portion of your femur and attach to the quadricep femoris tendon which connects to the patellar tendon. The function of this muscle is to extend the leg via the knee joint as well as stabilization and tracking of the patella.