The Anatomy of the Vastus Medialis

The vastus medialis oblique (VMO) of the quads extends the knee

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The vastus medialis is one of the four quadriceps muscles in the front of your upper thigh. The muscle, also known as the vastus medialis oblique (VMO), is a major player in moving your knee joint and stabilizing your kneecap. Injury to the teardrop-shaped vastus medialis muscle may cause knee pain and difficulty walking, running, or managing stairs.


The vastus medialis originates from the intertrochanteric line on the inner part of your femur (thigh bone). It then courses down the front and inner portion of the kneecap and joins the other quadriceps muscles (rectus femoris, vastus intermedius, and vastus lateralis) as the quadriceps tendon. The vastus then envelopes the kneecap and inserts as the patellar tendon on the front aspect of your tibia (shin bone).

The vastus medialis is innervated by the femoral nerve. This nerve arises from your lumbar spine at level two, three, and four. The femoral artery supplies blood to the vastus medialis.

Since the vastus medialis is a superficial quadriceps muscle, it is easily located and palpated. To find your vastus medialis, simply extend your knee as far as you can and tighten your quadriceps. Touch your kneecap and move your hand a couple of inches up and to the inner part of your thigh. The teardrop-shaped muscle is the vastus.


The vastus medialis serves to extend your knee joint. It works with the other quadriceps muscles to accomplish this task.

Since the muscle and its associated tendon course over the inner aspect of your kneecap, it also helps to stabilize your kneecap. Your kneecap, also known as the patella, is situated in a small groove on the end of your thigh bone. This groove allows the patella to track up and down while you bend and straighten your knee. The VMO helps to provide medial stability to the patella while it is tracking in the groove.

Associated Conditions

There are several conditions in your body that may affect the function of your vastus medialis. These may cause weakness in the muscle and may affect how your knee moves and how you are able to walk or run.

  • Patellofemoral stress syndrome (PFSS). Patellofemoral stress syndrome occurs when your kneecap fails to track properly in the femoral groove. This results in pain around your kneecap and makes jumping, walking, or running difficult or impossible. Since the VMO is a major stabilizer of your kneecap, weakness here may be a cause of PFSS.
  • Femoral nerve injury. An injury to your femoral nerve can cause paralysis or paresis of your quads and vastus medialis. Your femoral nerve arises from your lower lumbar spine, and things like arthritis, a herniated disc, or spinal tumor may cause nerve injury here. The resulting weakness may make straightening your knee difficult or impossible. This may affect your ability to walk, rise from a chair, or climb stairs.
  • VMO weakness after surgery or injury. If you have knee surgery, there will likely be swelling around your knee joint. When this occurs, some of the muscles that support your knee may become neurologically inhibited. The vastus medialis may be one of these muscles that become weak after knee surgery or injury.
  • Patellar dislocation or subluxation. If you have suffered a patellar dislocation, your vastus medialis may become injured or torn. This may cause pain, weakness in the muscle, and difficulty with walking or running.
  • Vastus strain due to trauma. A sudden blow to your thigh may result in a muscle strain to the VMO. This may cause pain, swelling around your muscle, and weakness in the vastus medialis.
  • Plica syndrome. There is a small fold of tissue that surrounds part of your kneecap called a plica. This can become pinched between your kneecap and femoral groove, causing pain. Your VMO is a stabilizer of your kneecap and helps to keep it in place, preventing pinching of the plica.

If you have knee pain or weakness in your vastus medialis muscle, you should visit your physical therapist or physician. He or she can determine the cause of your problem and can help you get on the road to recovery.


An injury to your knee or vastus medialis muscle may limit your ability to function normally. Rehabilitation for your vastus depends on the type of injury sustained and your specific needs and impairments.

In general, an acute injury to your vastus medialis should allow for some time to rest and heal followed by gentle movement to regain normal function. Exercises to improve muscle flexibility and strength may also be done to fully regain mobility and function and to prevent future problems with your VMO. Most injuries to your vastus medialis take about six to eight weeks to fully recover.

Vastus Medialis Strain

A tear or strain to your vastus medialis requires about seven to 10 days of rest. During this time, you may need a knee brace or compression sleeve to support your knee and control swelling. After a week of rest, gentle exercise can be done to regain knee mobility and vastus function. Exercises may include heel slides, quad sets, and straight leg raises. Stretching for your quad may be done to gently elongate the muscle.

VMO Weakness From Femoral Nerve Injury

Your femoral nerve may become pinched by arthritis or a bulging disc in your back. This may cause vastus medialis weakness and limit your ability to walk. Treatment for this first involves getting pressure off your femoral nerve to restore normal nerve communication with the VMO. Once the nerve is freed, strengthening exercises for the vastus medialis can be done to regain normal knee function.

Patellofemora Stress Syndrome

The vastus medialis is a major knee stabilizer, and weakness to the muscle may be one cause of PFSS. Treatment of PFSS involves improving vastus strength with quad sets, straight leg raises, and patellar tracking exercises. Your gluteus medius, a hip muscle, also controls the position of your knee, so working to strengthen this muscle in conjunction with your vastus may be done to treat PFSS.

Vastus Inhibition After Injury or Surgery

Swelling is common after a knee injury or surgery, and this swelling may inhibit function of your quad and vastus medialis. When this occurs, treatment to reduce swelling in your knee may be required. Heat or ice may be used, and exercises like heels slides and stationary bike riding may help.

Working to improve vastus medialis function with a physical therapist may be helpful. A special type of neuromuscular electrical stimulation (NMES) may be used to help your vastus contract properly to regain normal function of the muscle.

Keep in mind that everyone is different and people heal at different rates. Be sure to work with your physician and PT after injury to understand your course of rehab for your vastus medialis and knee. Realistic expectations and goals can keep you motivated during your recovery.

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