Vastus Medialis Oblique (VMO) is one of four quadriceps muscles. Your VMO sits medially or on the inside of your thigh. Its primary function is to extend the knee.
Structure: The VMO is a muscle located in the anterior (front) compartment of the thigh. The other three muscles that make up our quadriceps are the vastus lateralis, vastus intermedius and rectus femoris.
- Origin of the VMO: Medial side of the femur (thigh bone)
- Insertion: Quadriceps tendon near the knee
- Artery: Femoral artery
- Nerve: Femoral nerve
- Actions: Knee extension (straightening the knee)
The VMO originates from a continuous line of attachment along the thigh bone and inserts into the quadriceps tendon on the inside border of the knee cap.
Function: Not only does VMO extend the knee, but it also has a very important function in correct knee-cap tracking. When the quadriceps contract and pull on their insertion points at the patella (knee cap), this causes and upward tracking of the knee cap in the femoral groove. If the quadriceps are functioning correctly they should contract simultaneously and the patella should track smoothly and upwardly through the femoral groove. Unfortunately, this smooth upwards pull of the patella can be interrupted by a varying maladaptation’s in the system.
Clinical Significance: When there is acute inflammation there is often swelling and fluid within the joint capsule of the knee. This fluid inside the knee contributes to the inhibition of nerve signalling and inhibits the VMO muscle, which consequently results in weakness of the VMO. This weakness can then lead to further secondary issues such as biomechanical imbalances due to tight or weak structures. A good example of this is poor patella tracking. This highlights the importance of reducing joint swelling for acute injuries. Reduce swelling to reduce the loss of strength or atrophy of the VMO muscle to prevent secondary issues during your rehab.
- Isometric Contraction: Sitting on your bed or floor with legs out straight, place a towel underneath your knee. Flex your quads muscle with hip/leg slightly externally rotated. Hold contraction for 5-10 seconds, place your fingers on your VMO to ensure your quads muscle is activating and firing. Try 10 reps for 10 seconds and as your strength/endurance improves increase the length of your contractions.
- Seated Isometric VMO and Adduction: Sit on a chair or platform where your feet hang freely. Place a ball between your thighs and squeeze the ball together activating your VMO. Hold your contraction for 10 seconds. Again, feel your VMO to ensure its activation and increase length of contraction as you become stronger.
- Externally Rotated ½ Squats: Stand with your legs shoulder-width apart with knees and feet externally rotated (turned outwards). Squat halfway down and come up nice and slowly, focusing on activating the VMO to bring you back up to a standing position. Do 3 sets of 10 and increase as you become stronger.
- Wall/Ball Squats: Place a Swiss ball on your back against the wall. Slowly squat down into a near-seated position so that your thighs are parallel with the ground. Slowly come back up, avoid locking your knees, 3 sets of 10 and increase as you become stronger.
- Split Squats/Static Lunges: Start with your feet shoulder-width apart and take one large step forward. You can place your hands on your hips or to make it harder you can hold dumbbells by your side. With an upright posture, lunge down and up without your knee at the front moving in front of your big toe. Focus on putting most of the weight through your front heel and don’t let your knee buckle in.
- Single Leg Squats: Single leg stability is somewhat advanced and should only be done when you are pain-free and finding bilateral exercises easy. If you are looking to get back into running or return to sport these are a must!
- Step-Ups: Standing in front of a bench or chair, step up onto a platform and drive from the gluteal muscle, not from your toe. Ensure your knee is not buckling inwards and is forced/pushed out. Slowly step down making sure your knee is in a stable neutral position and your VMO muscle is contracted. Alternating legs, repeat 3 x 10-15.
If you are experiencing knee pain and think you might need to strengthen your VMO or just want a proper diagnosis for your knee pain book in to see one of our Sports Physios at Bend + Mend in Sydney’s CBD.