The Seven Best Exercises For VMO Activation: Early Knee Rehab

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.

How to work your VMO:

  1. 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.
  2. 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.
  3. Externally rotated ½ squats: Stand with your legs shoulder width apart with knees and feet externally rotated or turned out. Squat half way down and come up nice slowly focusing on activating VMO to bring you back up to standing position. Do 3 sets of 10 and increase as you become stronger.
  4. Wall/Ball Squats: Place a swiss ball on your back against the wall. Slowly squat sown 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 ten and increase as you become stronger.
  5. 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.
  6. Single leg squats: Single leg stability is somewhat advanced and should only do 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!
  7. Step ups: Standing in front of a bench or chair, step up on to the 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.


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  • Betty says:

    This has been most helpful. As a personal trainer with a certification in corrective exercise, knowledge and practice application are valuable to my clients. This was written in a way that was easy to understand and execute. Thank you

  • Stephen R Mandler says:

    If you have had a surgery that left scar tissue midline of the vastus medialis (superficially separating it into down the middle)-Bilateral fasciotomy from an anterior thigh compartment syndrome 10 ys ago, can a resistance-based workout aimed at hypertrophy restore that muscle to normal function and appearance?

  • Hi Stephen,
    Thank you for your question.
    Resistance exercise programming with hypertrophic focus (8-12 repetitions 75-85% of 1RM) is a widely prescribed to increase muscle mass and strength. Due to the scar tissue down the mid-line, I cannot confidently say that the appearance will restore 100% to “normal”, but if you are looking to increase the total muscle mass and function, then this exercise programming will achieve that.
    Resistance exercise is a safe and effective intervention to improve muscular function. I believe this should be the focus with rehabilitation and restoring the muscular control and strength. The effectiveness of the exercise intervention may be influenced by the injury history of the lower leg; therefore, rehabilitation should be guided by your Physiotherapist.
    If you have any further questions please let me know.
    Kind regards,

  • Ella says:

    So this swelling after injury impeding this muscle then would finally explain why for a long time after partial acl tear and partial meniscus tear which did not require surgery ( for which I reduced weight bearing for a long time doing mostly swimming and light walking and was limping a lot at first. ) I started to have pain and aching, sometimes burning pain on the medial knee but above the joint line this time and it always also radiated halfway up my thigh at rest and during activity especially after a lot of walking or walking up and down hills…. compression knee brace helps. starting ballet again has seemed to help, which strengthening quads should according to this article. I also found out after trip to podiatrist for ankle pain that I pronate when walking and recently got custom shoe inserts which have seemed to help too. The ortho could not explain it finally your sight has provided insight and I will look into additional physical therapy.

  • Mark Osborne says:

    Thanks this stuff is helpful.
    After a stroke last year my left knee is weak and I think I need to strengthen my VMO?
    I guess I wonder how many days of daily exercises starts to make a noticeable difference. Would the muscle feel notably harder than on the other side?

    • Hi Mark,

      Thank you for your question,
      The vastus medialis muscle works along with the 3 other quadricep muscles to straighten the knee, although the vastus medialis muscle is particularly important with the terminal extension of the knee, where it helps to “lock out” the knee. If stairs or standing from sitting are tasks that you are having issues with, then quadricep strengthening, and Vastus Medialis strengthening will be greatly helpful.
      With regards to how long it will take to see result; this depends. If you are performing appropriate quadricep/VMO strengthening exercises, then increased strength of those exercises may be seen in as little as a few weeks to month. If you are looking to increase muscle size/volume, this may take longer 8-12+ weeks. It may feel like following an exercise session that the muscle is bigger, but this will most likely be due to increased blood flow into the muscle.
      Influence of age will play a role on muscle development. After the age of 30, individuals can lose 3-5% of muscle mass per decade due to a process known as sarcopenia. Fortunately, Progressive resistance training is a way of slowing down this process.
      Muscle Firmness is something that can be related to muscle tone, whether this is related to the stroke I’m not 100% sure without assessing. If this is something that is concerning you, I would seek further clarification in a clinical setting with GP, Neurologist or Physiotherapist.
      The key importance to remember is that strength increase can be achieved within a few weeks, but muscle growth will take a longer period of time. I highly recommend seeking a physiotherapist or exercise physiologist to develop your initial exercise program, so that you are performing adequate and appropriate strength exercises tailored to your needs.

  • Todd Herman says:

    Thank you Patrick for your comments. I train for Spartan races by running both on both flat and mountain terrain between 5 and 15 miles. I build up week by week to attain the longer distances. On occasion I get a pain in my VMO. It may occur on one side at a time or in both. The pain does not feel like a cramp as I have experienced in my calves or feet (pain and locking up). It seems to happen if I extend my self to far when I add miles on my run compared to previous distances. My question is it simply muscle fatigue? Why do my other muscles not experience this issue? I have not had any knee issues so I do not believe that is an underlying issue? If it is not fatigue is there something else it could be? I will start performing your exercises listed above. Thanks again. Todd

    • Hi Todd,
      Thank you for your comment.
      Anterior knee pain is unfortunately a common symptom experienced in casual and experienced runners.
      From your detailed explanation, there are 3 things that may be influencing your knee pain.
      1. Fatigue/Muscular fatigue with the increased mileage. Strengthening exercises will assist with improving running efficiency and muscular performance. A minimum of 8-12 weeks of resistance based exercise is required to achieve this performance goal. You can perform these exercises as an adjunct, concurrently with your running training.
      2. The Surface, as you said you train for Spartan – often on uneven/mountain terrain. The change of gradient has a significant impact on muscular usage. An article in 2019 shows that both incline and decline gradients have a significant increase in Quadriceps muscular activity. This increase of 4-8% quadriceps/lower limb muscular loading over 10-15miles may be key in the cause of the medial knee pain. Similar to the reason above, I believe a strengthening program of the lower limb will assist with this.
      3. Finally, an alternative cause of your symptoms may be the patellofemoral joint (Kneecap and Femur). The patellofemoral joint pain is the most common cause of anterior knee pain, particularly in runners. Therefore a thorough knee assessment is often required to assess the root cause of the issue.

      Hoping this helps with your question Todd, by the sounds of things you are going about your goal of Spartan Running the right way, being consistent with gradual progressive loading. Lower limb strengthening will provide you with improved running efficiency and performance, although I recommend that you consider the whole leg with your strength program.

      A previous blog on strength training benefits for runners can be found at:

      Also some additional reading from Physio Campbell, where he discusses lower limb strength exercises – with examples of exercises, over a 3 part series.

      If you are a Sydney Local, you should pop into one of our 4 CBD clinics for an assessment of your knee pain, so that we can keep you achieving your goals painfree.

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