The rectus femoris is a large muscle positioned straight down the front of the thigh.
The rectus femoris 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.
Knee joint extension.