Knee Function: Anterior Muscles

This week I’m writing about the function of the knee. Today, I’m going to address the anterior muscles.

These muscles are strong, and their orientation to the joint enables large movements with just a small muscle contraction. These large muscle masses combine with a lever to produce velocity and make way for powerful and quick movements.

Rectus Femoris

The rectus femoris covers a large portion of the middle of the thigh. It completely covers the deeper vastus intermedius and a large portion of the other two vasti. In a lean individual, a strong knee extension will reveal the V-shaped muscle. This muscle lies between the vastus medialis and vastus lateralis.

Vastus Lateralis

This muscle, sometimes called the vastus externus, is attached to the femur, down to the patella (knee cap), and on to the tibial tuberosity. It has one function: to extend the knee. A simple, strong extension of the knee will make the vastus lateralis visually apparent about two inches above and lateral to the knee.

Vastus Medialis

This muscle, in my opinion, is the most attractive muslce in the human body. Known to many as the “tear drop”, it attachs from the inner side of the femur, along the entire length of the linea aspera, and to the upper three-quarters of the femur. It also attaches to the patella and to the tibial tuberosity. It has an identical function to the vastus lateralis: extension of the knee

Vastus Intermedius

Sometimes referred to as the vastus cruraeus, this muscle attaches along the surfaces of the upper two-thirds of the femur. The intermedius lies under the rectus femoris. It is a deep muscle and is active in the same function of knee extension.

Tensor Vastus Intermedius

The vasti group has a newly discovered tensor called the tensor vastus intermedius. This muscle lies between the vastus intermedius and vastus lateralis. Previously, it was assumed to be a very small head of the vastus intermedius, but a 2016 study showed the tensor vastus intermedius arises along the upper surface of the femur with a unique, long thin tendon crossing the length of the femur. It then attaches to the patella. This arrangement, along with the small size of the muscle, suggests the tensor vastus intermedius aids in controlling the position of the patella rather than directly contributing to knee extension.

More to come…



3 Rounds For Time:
75 Double Unders
20 Double Dumbbell Deadlifts

Other Articles In This Series:
1. Knee Function: Four Bones, Two Directions
2. Knee Function: Anterior Muscles
3. Knee Function: Posterior Muscles

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