Location, Location, Location
The vastus medialis muscle is one of four quadriceps muscles. It is located on the inner part of the front of the thigh. It attaches to the medial aspect of the femur and runs along the inner front down to the base of the patella, or kneecap, via the quadriceps tendon and by the patellar tendon onto the tibal tuberosity. The lowest part of the vastus medialis, called the vastus medialis oblique (VMO), achieves its maximum contraction during full extension.
It's Vastly Important
The vastus medialis works along with the vastus lateralis to stabilize the kneecap. The VMO helps to keep the kneecap in its grove, which is located on the lower part of the femur, by pulling it inwards. The vastus medialis muscle, along with the other quadriceps muscles, also extends the leg at the knee to a straightened position.
An Indication of Weakness
When the vastus medialis or VMO muscle is weak, the kneecap moves in an abnormal way and can even be positioned abnormally as well. This creates a chronically unstable kneecap. Improper tracking of the kneecap can cause wear to the inferior surface. You'll feel the most pain during exercises requiring the leg to extend more than 20 or 30 degrees.
Make It Stronger
You can strengthen the vastus medialis through full range of motion exercises because this muscle is activated fully during the last degrees of knee extension. Closed chain exercises like the leg press and squat are safer to use for strengthening the vastus medialis muscle than open chain exercises like leg extensions. An easy way to strengthen the vastus medialis is to stand with both legs straight and to contract the quads. This contraction raises the kneecaps and uses the VMO and vastus medialis muscle. Hold the contraction for 10 seconds, then relax and repeat. Another exercise requires you to sit on the floor with a pillow underneath each knee so that they are at a 135-degree angle. Slowly extend the leg at the knee until it is completely straight, fully contracting the quads so the kneecap is pulled upwards. Make this exercise more difficult by placing a 5-pound weight on the ankles. Complete 3 sets of 10 and work on increasing the weight instead of the number of reps.
Brace Yourself, Prevent Another Injury
A knee brace stabilizes the patella and can be very helpful for those who either fully or partially dislocated their kneecap, also known as patellar subluxation. These braces help by keeping the kneecap in the femoral grove and by minimizing the feeling of patellar instability. This can also help by creating a feeling of security for those who have a fear of re-injury.