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The quadriceps muscles are a popular group, for good reason. These muscles are a powerful part of both our movement and posture. When you combine all four of the quadriceps muscles together you have the largest group of muscles by volume in the body as well as the strongest group of muscles. Because they are superficial, meaning close to the surface, people are often familiar with the general location and action of these muscles. In this article, we’ll help you get a little more specific. You’ll learn where the quadriceps attach and understand how they come together to create movement.
What muscles are included in this group?
These muscles are sometimes referred to collectively as the quadriceps femoris muscle. However, they are really four distinct muscles throughout most of their length that merge into a single tendinous attachment at the distal end. Each of the muscle sections is typically referred to by its individual muscle name.
The four muscles in this group include:
- Rectus femoris
- Vastus lateralis
- Vastus medialis
- Vastus intermedius
There is some variability in muscle morphology between individuals, however. Although the typical quadriceps has four muscle bellies (hence the name), some people have more than four muscle bellies making up the muscle group on their anterior thigh.
Quadriceps muscle attachments
Among the four muscles in this group, rectus femoris is the most superficial muscle. It lies over the top of part of vastus lateralis, part of vastus medialis, and all of vastus intermedius. Vastus intermedius lies between vastus lateralis and vastus medialis. Rectus femoris is the only one of the quadriceps that crosses the hip joint.
Proximal attachments
Specifically, rectus femoris attaches at its proximal end to the anterior inferior iliac spine of the pelvis and the supraacetabular groove. The other three of the four muscles attach to various locations on the femur at their proximal ends.
At its proximal end, vastus medialis attaches to the intertrochanteric line, pectineal line of the femur, medial lip of the linea aspera, medial supracondylar line of the femur, and the medial aspect of the femoral shaft. Vastus lateralis also has several attachments at its proximal end. They include the intertrochanteric line of the femur, greater trochanter, gluteal tuberosity, and the lateral lip of the linea aspera of the femur. Finally, the last of the quadriceps, vastus intermedius attaches to the anterior and lateral surfaces of the femoral shaft at its proximal end.
Distal attachments
All four muscles merge into a single tendinous attachment at the distal end just before they attach to the patella via the quadriceps tendon. They then continue on to attach to the tibial tuberosity of the tibia via the patellar ligament.
Actions of the quadriceps muscles
All four of these muscles are primary extenders of the knee joint. One, rectus femoris also contributes to hip flexion. It’s the most superficial of the muscles that flex the hip, so it often functions in activities like yoga as a restrictor to hip extension (such as in back bending) in addition to doing hip flexion.
The combined action of the four quadriceps muscles is essential for all movement of the kinetic chain of the lower limb. That includes activities like walking, running, climbing stairs, playing just about any sport, and getting up and down from the floor, a chair, or the car. Because the four quadriceps muscles form the quadriceps tendon which lies over the patella, the balance of tension between these four muscles is also important for stabilization and tracking of the patella in the knee. Additionally, the quadriceps muscles contribute to maintaining our posture.
Conclusion
The quadriceps are large powerful muscles that are essential for everyday movement as well as sports and athletic activities. A clearer understanding of where each of these muscles attach and what joints they cross can help you better understand why they influence the specific types of movement that they do.
References
Chaitow, L. and J. DeLany. 2011. Chapter 13: The Knee. In Clinical Application of Neuromuscular Techniques. Volume 2 – The Lower Body (Second Edition). New York, NY: Churchill Livingstone Publishing.