The importance of quadriceps – What is the VMO?

At Longevity Personal Training and Exercise Physiology Edgecliff, Lindfield, Marrickville and Randwick, we are constantly asked what are the quardicep muscles, in particular the VMO and what it’s function is.

What are your quadriceps?

Your quadriceps are a group of 4 muscles running down the front of your thigh. One of these muscles, the rectus femoris, originates at your hip bone while the other 3 muscles, the vastus intermedius, vastus lateralis, and vastus medialis (often referred to as your VMO) originate on your femur. All quadriceps muscles insert at the patella, aka the kneecap. The function of the quadriceps is to flex the hip (rectus femoris) and extend the knee (all 4 muscles). The quadriceps also play a major role in patellar stability and proper patellar tracking during dynamic movements, including walking!

Run, it’s Quadzilla!

Why does the kneecap matter?

Your kneecap increases the moment arm for your quadriceps to work, meaning that you can extend your knee much more powerfully than you would be able to without the kneecap there. The kneecap is of particular concern when looking at the knee because it is a sesamoid bone, meaning that the only thing keeping it in it’s home (a specialized groove on the bottom of the femur) is the proper functioning of the quadriceps muscles.


All quads are not created equal

With respect to the quadriceps, we often see a common movement pattern arise; over-reliance on your lateral quadriceps muscle (vastus lateralis) and an under-reliance on your medial quadriceps muscles (vastus medialis). Over time, this ever so slight activation difference can begin to pull your kneecap to the outside of the groove on the femur. This will present with very little issue short term, but over time you are predisposed to patellofemoral pain syndrome, or ‘runners knee’.


Pre and post surgery size difference of the VMO muscle.


How can I avoid this?

Activation — If you experience pain in and around the kneecap when you are exercising, beginning your session with exercises (such as terminal knee extensions) to target your vastus medialis (VMO) could benefit you. This will make the muscle more excitable and more likely to pull your kneecap into alignment.

Strengthen — To strengthen your VMO and produce long-lasting change, exercises involving a significant knee bend are your best bet. These include squats (and squat variations), leg extensions and leg press. Focusing on full range of motion will improve strength and coordination of your quadriceps musculature to stabilize the patella and improve knee health.

Daniel illustrating the terminal knee extension exercise.

If you feel as though you suffer from runners knee or you might be predisposed to this condition, it is important to consult with an Accredited Exercise Physiologist to assess, program and progress your exercise to your individual needs.


Contact Longevity Personal Training and Exercise Physiology to get started — 1300 964 002


Written by Mitchell Hooper

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