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The Quadriceps Muscle Group

Posted by KinX Learning on August 29, 2016 . 0 Comments

The quadriceps muscle group includes the rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius muscles, which extend the knee. 

The vastus muscles run almost the entire length of the femur and converge into the quadriceps femoris tendon, which attaches to the patella bone (kneecap). The vastus lateralis is a large muscle located halfway down the outer side of the thigh. It originates on the lateral surface of the femur from just below the upper head of the bone to almost the lower end. 

The vastus medialis is located on the medial (inner) side of the thigh, somewhat lower than the lateralis, and is partially covered by the rectus femoris. It originates on the medial side of almost the entire shaft of the femur. 

The vastus intermedius is a close associate of the vastus medialis and lateralis. It lies between them and beneath the rectus femoris. It is difficult to see this muscle separate from the medialis and often the two are continuous for part of their length. The vastus intermedius originates on the anterior and lateral sides of the femur, running almost the entire length of the shaft of the femur. 

The rectus femoris is a large muscle positioned straight down the front of the thigh. It originates on the spine of the ilium bone of the pelvic girdle. Because of this attachment, it has an action at the hip joint as well as the knee joint. At the lower end the rectus femoris joins the tendons of the four vastus muscles merging together onto the patella bone and surrounding ligaments. 

The patella, however, is a free-floating bone and attaches to the tibia via the patella ligament. This ligament, for all practical purposes, acts as though it were a tendon. It changes the angle of insertion which makes the quadriceps muscle stronger in the initial stages of execution.