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Functions and anatomy of the rectus femoris muscle shown with 3D model animation.
Hey everyone! It's Nicole from Kenhub, and in this tutorial, we'll be looking at the anatomy and functions of the rectus femoris muscle – the muscle which you can now see isolated on the screen. Before we look at the functions and the movements of the rectus femoris muscle, let’s first look at its anatomy.
As you can see in the image, the rectus femoris muscle is a long superficial muscle which runs from your pelvis straight down the thigh to end at the knee or specifically at the kneecap or patella. Like many structures in anatomy, this basic detail actually determines the name of the muscle which in Latin is called musculus rectus femoris which means straight muscle of the thigh.
The rectus femoris muscle is part of the major muscle group of the anterior thigh which is, of course, the quadriceps femoris muscle group. As the name quadriceps femoris suggests, there are four muscles in this group with the rectus femoris muscle being the most anterior and superficial of the group.
Looking briefly at the innervation of the rectus femoris muscle, like most other muscles of the anterior compartment of the thigh, the rectus femoris muscle is innervated by the femoral nerve, seen here highlighted in green on the image. The femoral nerve originates from the lumbar plexus specifically the anterior rami of the second through fourth lumbar nerves.
When we take a closer look at the rectus femoris muscle, we can see that it has a double origin on the ilium. The first is a straight tendon which arises from the anterior inferior iliac spine and the other, a reflected tendon which arises just superior to acetabulum.
The rectus muscle continues from its origin into a long thin cylindrical belly. On the anterior aspect of the muscle, the fibers are arranged in a bipennate arrangement – meaning, the fibers converge diagonally on either side of the muscle – kind of like the barbs of a feather. On the posterior aspect, however, the fibers run more parallel to one another along the length of the muscle.
Moving on to the distal attachment of the rectus femoris muscle, we can see the muscle ends in a long thick flat tendon which joins the tendons of the other quadriceps muscles and attaches to the base of the patella. Some fibers of the quadriceps tendon extend over the patella and blend with the patellar ligament which joins the patella with the tibia.
Having looked at the attachment sites of the rectus femoris muscle, we can now guess what joints are going to move while the rectus femoris muscle is contracting – the hip joint, which is formed by the head of the femur and the acetabulum, and the knee joint which is the meeting point of the distal end of the femur with the proximal end of the tibia and, of course, the patella. It’s worth mentioning that the rectus femoris muscle is the only member of the quadriceps femoris muscle group which acts on the hip joint as all the other muscles of this group only act on the knee.
Now let’s discuss the functions of the rectus femoris muscle.
The first movement which the rectus femoris muscle is involved in is flexion of the thigh at the hip joint, which brings the thigh forward or to the front of the body. The second movement we’re going to talk about is the extension of the leg at the knee joint. As we can see here, this causes the knee to be straightened out so that the thigh and the leg are in line with one another.
To give a functional example of the rectus femoris muscle in action, the best examples of both functions working is when kicking a football as we can see here in the image. Before kicking the ball, the rectus femoris muscle pulls or flexes the extended thigh forward from behind while extending the leg at the same time. This is why this muscle may often be known as the kicker’s muscle which is good to know for all you aspiring Cristiano Ronaldos out there.
So now that we’re finished talking about the rectus femoris muscle and its functions, let’s recap.
The rectus femoris muscle has two primary functions which happen at the hip joint and at the knee joint – that is, flexion of the thigh and extension of the leg.
So that’s it for this video of the functions of the rectus femoris muscle. Don’t forget to visit kenhub.com for more videos and tutorials.