The vastus medialis oblique muscle, more commonly called the VMO, sits above your knee on the inner front part of your thigh. While usually associated with assisting in leg extension, the results of a 2007 study published in "Medicine and Science in Sports and Exercise" indicate that the VMO also plays a key role in knee tracking and knee stability.
The VMO is often the weakest muscle in the quadriceps group, says sports medicine specialists at the Poliquin Performance Center in Chicago. It is usually the first part of the muscle to atrophy, and the last to rehabilitate. The VMO is most active during the last 10 to 15 degrees of leg extension. Injuries such as anterior cruciate ligament tears, patella dislocation and meniscal tears may impede VMO function, and cause chronic knee pain.
Basic VMO Exercise
Before performing advanced VMO exercises, specialists on the Sports Injury Clinic website suggest checking to see if the muscle group is functioning properly. Sit with your legs extended in front of you, with a towel placed under the back of one knee. Start with the knee slightly bent. Place your fingers on your VMO, and press down against the towel to extend your leg. If the muscle is activating correctly, you will feel it contract under your fingers. If you don't feel the VMO contract, it may not be strong enough for weight-bearing exercise. This sometimes happens after anterior cruciate ligament surgery. Continue practicing the towel pressing exercise until the muscle gains strength. Perform 20 repetitions every day.
If your doctor or physical therapist advises against weight-bearing exercise, assume a supine position with one knee bent, and the foot placed fat on the floor. Extend the leg toward the ceiling, and wrap a resistance band around your foot. Hold the ends of the band with both hands, and press both of your elbows firmly into the floor. Slowly bend your knee to a 20-degree angle, and then extend your leg against the band's resistance. Add challenge by using a heavier resistance band. Perform 15 repetitions on each leg.
The Poliquin Performance Center uses an unusual exercise called the Petersen sled drag for vastus medialis oblique rehabilitation and knee injury prevention. The sled consists of a metal platform, with a bar in the middle for attaching barbell plates, and a chain or heavy rope to pull the sled. After placing the weight plates on the sled, hold the rope or chain with your arms relaxed and extended. Keep your legs close together, with your feet slightly turned out. Drag the sled as you take small steps and walk backward for about 25 feet. Lift your heels from the floor as you walk. Perform four sets.