The theory behind strengthening the VMO, or vastus medialis obliquus, is based upon the muscle's line of pull that acts upon the patella during knee movement. When the knee is bent the vastus lateralis muscle pulls the patella laterally from the femoral groove meant to hold the patella. This action should be countered by equal pull from the VMO. When the VMO is unable or unwilling to perform this action the patella can be pulled awry, leading to dislocation, pain or a variety of other injuries. As a result the VMO is the target of many rehabilitation programs.
Quadriceps Isometric Sets
Lie on your back with your legs out straight. To exercise the VMO contract your quadriceps by attempting to pull your knee cap toward your hip or upward toward your quads. Hold this contraction for a few seconds and then relax and repeat. Three to eight sets of 10 repetitions performed three times daily work best, according to physical therapist Teri Mingee.
Straight Leg Lifts
To perform a leg lift, sit or lie down on your back. Contract your quadriceps to stabilize your knee cap and then lift your heel up off the floor while keeping the knee straight. The heads of the quadriceps will fire to lift the leg up off the ground. Perform 10 to 15 repetitions using your body weight or an ankle weight.
Shallow squats that bend the knee joint about 30 degrees are also recommended commonly for VMO strengthening. These squats are commonly prescribed because the patella does not need to be stabilized in this range of motion. According to orthopedist Scott Welsh, once the knee flexes 30 degrees the VMO and vastus lateralis muscles must oppose each other to allow the patella to track properly into the intercondylar notch on the femur. If the patella does not track properly, pain is the likely outcome.
Hamstring and Gastrocnemius Stretches
The hamstrings and calf muscles should be stretched during any VMO program. These muscles oppose the actions of the quads when they are overly tight, so stretching them can allow the quadriceps to better perform their duties. Stretch the calf by placing the ball of your foot against the floorboard while in a standing posture and leaning your body weight forward while keeping a straight knee. The hamstrings can be stretched a multitude of ways, however the easiest and most common method involves reaching for your toes while in a seated position. To ensure that you are stretching your hamstrings and not your lower back, imagine tipping your pelvis forward to reach for your feet. Hold each of these stretches for about 30 seconds and repeat several times.
Several physical therapists do not believe isolating the VMO is the proper means of rehabilitating patella injuries. Physical therapist Doug Kelsey is part of this group. He notes research indicating the VMO cannot be isolated from the other quadriceps muscles. This group of physical therapists favors overall strengthening of the knees during weight bearing movements as a means of therapy.