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Quads 101: Anatomy, Actions, & Functions

Quads 101: Anatomy, Actions, & Functions

Quads 101: Anatomy, Actions, & Functions

Many bodybuilders go through leg day even though they are not really excited about this routine. After all, having strong and shapely legs is almost everyone’s goal. It does not just make you look good in a pair of jeans or shorts but it also implies athleticism.

Quadriceps femoris, popularly known as quads, is a critical factor if you want to achieve sculpted strong legs. This group of muscles makes up the entire front of your thighs. Aside from its aesthetic purpose, it also helps in powering everyday movement.

Quad muscle plays a vital role in your daily movement. From one-off efforts like standing up from the toilet or getting out of your car. They are also important on active motions like running and walking.

Let’s get to know this amazing group of muscles a little better.

Quads 101: Overview

Image from Wikimedia Commons

Quadriceps femoris is a group of muscles that largely cover the front and sides of the thigh. This muscle group is more commonly referred to as the ‘quads’. The quads are great extensors of the knee joint and occupy the bulk of the anterior thigh. They cover almost the majority of the anterior and both the medial and lateral sides of the femur.

The name ‘quadriceps femoris’ means ‘four headed femoral muscle’. It consists of four individual muscles – rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius. Rectus femoris can be found in the midline, while vastus lateralis occupies the bulk of the lateral thigh. Vastus medialis is located in the medial thigh while vastus intermedius lies between medialis and vastus lateralis.

The quad muscles belong to an extremely powerful muscle group which plays vital roles in motions like climbing, jumping, running and walking. They also help stabilize the patella during movement. In addition, they contribute in flexion of the thigh at the knee joint.

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Quads 101: Anatomy

Let’s take a thorough look at the four individual muscles that make up the quadriceps femoris.

Image from Wikimedia Commons

Rectus Femoris

The rectus femoris is a fusiform muscle which means the tendons of muscle tapers narrows on both ends. It’s the only muscle amongst the four individual quad muscles that crosses both the knee joint and hip.

The rectus femoris has two heads and points of origins – from a groove on the ilium above the acetabulum and anterior inferior iliac spine.

The word “rectus” is derived from a Latin word which means straight. Rectus femoris got its name because it runs straight down the thigh. Since it crosses over the hip and knee joint, it serves as a two-way acting muscle. It aids iliopsoas in hip flexion and contributes to 90° of knee flexion.

Image from Wikimedia Commons

Vastus Lateralis

The vastus lateralis muscle is the largest of the four quads muscles. It serves as an extensor of the leg at the knee just like the other muscles in the group. The term means “huge lateral”. It got its name because of its location on the lateral side of the thigh and enormous size.  

The muscle attaches to the femur on the upper end. This attaches to the patella or kneecap on the lower end.  It originates from the external lip of the linea aspera located on the femur’s posterior surface. It passes over the knee and makes an insertion onto the tibial tuberosity along with other quads muscles.

Its main function is to aid in the extension of the knee.

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Vastus Medialis

Another part of the quadriceps muscles is the vastus medialis which can be found on the front of your thigh, just above the kneecap. This is the innermost muscle amongst the four. You will sometimes feel or see this muscle contract when you extend your leg fully.

This originates from a continuous line of attachment on the femur. It starts on the front and middle side on the intertrochanteric line of the femur and goes down and back along the pectineal line. It then goes down along the medial lip of the linea aspera and onto medial supracondylar line of your femur.

The vastus medialis aids in stabilizing your kneecap. It also helps in strengthening the muscles around your knees. It’s important that you keep your vastus medialis muscle strong if you want to avoid injury.

Vastus Intermedius

The last part of the quads muscle is the vastus intermedius. It is located in the anterior region of the thigh, between the lateralis and vastus medialis. It is situated below the rectus femoris.

This muscle originates from the upper two-thirds of femur’s anterior surface. It inserts onto the tibial tuberosity, along with the other muscles of quads. The main function of this particular muscle is to make an extension of the knee possible.

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Quads 101: Actions and Functions

Now that you know the anatomy of your quads, let’s try to see how important they are on your daily function. There’s more to these group of muscles than making you look good and strong.  

With every movement that you make with your legs, you must know that these movements involve your quads. That’s how relevant they are in your daily life. Your quads work harmoniously with other leg muscles to promote effective movement, such as cycling, squatting, running, and balance.

The primary function of your quads is to bend and straighten your knee. In addition, it is also involved in rotating the hips, particularly the rectus femoris muscle.

Your quads straighten your leg at knee point when they contract. You can feel your quads in action on the front part of your thigh when you straighten your knee a few times after sitting for some time.

Your quads also assist the kneecap in its proper position since they extend over the patella. They also help in bending up or flexion of your hip. In addition, your quads also play an important role when rising from a chair. Because of them, you are able to straighten your knee which is critical to rising up from a sitting position. Moreover, they are also essential for running and walking. They help in keeping you moving forward while running and walking. They also help so you avoid falling when standing still.


Your quads play a significant role in your body function. Without them, simple actions such as walking and running would be impossible. Make sure that you take care of your quads by performing exercises that aim to strengthen these group muscles.


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Rogers, P. (2019). Definition of the Quadriceps Muscles. Retrieved from

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