Knee pain is a common running injury. A rapid increased in mileage, hill training, weakness in the quadriceps, hip, glut, foot, and ankle musculature are contributing factors to knee pain. Lack of stabilization at the hip or lower leg places increased stress on the knee joint. The vastus medialis oblique (VMO) is a key stabilizing muscle during weight bearing knee flexion and extension and warrants further discussion.

What is the VMO?

The vastus medialis oblique (VMO) is one of four quadriceps muscles which extend the knee joint and stabilize the knee in weight bearing. The knee is a modified hinge joint which means it is more complicated than a door hinge. Subtle but important accessory motion occurs with movement in many extremity joints. Accessory rotation in the knee (the femur rotates slightly medially relative to a stationary tibia) occurs during weight bearing, and decreases joint wear and improves patella-femoral joint function. The VMO is the quadriceps muscle responsible for accessory joint motion during the final few degrees of knee joint extension. Building and maintaining strength in the VMO, therefore, is an important component of running without knee pain.

The VMO originates on the intertrochanteric line of the femur and adductor muscle aponeurosis and inserts on the quadriceps tendon and tibial tuberosity via the patellar tendon. The VMO is a difficult muscle to isolate during strengthening exercises due to its diminutive size andspecificity. Without adequate VMO strength, however, patella-femoral (knee cap) tracking shifts in a lateral direction during flexion and extension associated with running. Prolonged lateral knee patella tracking leads to irritation of the patella surface and inflammation of the surrounding tissue (patellar tendon, cartilage). While prior joint trauma, osteoarthritis, meniscus injury, and overtraining can also lead to knee pain in runners, the VMO must be addressed during conservative treatment and injury prevention. Additional treatments such as patella-femoral taping and video running analysis may reveal underlying asymmetries which contribute to knee pain.

VMO-Specific Strengthening

1. Terminal Knee Extension:
Weight bearing terminal knee extension (TKE) isolates the stabilizing VMO and (if done correctly) facilitates the necessary accessory motion of the knee joint. Emphasis should be on straightening the knee using the quadriceps muscles rather than attempting to “lock” the knee.

2. Eccentric Quadriceps Strengthening:
Strengthening the quadriceps in a functional loading position is important for runners. Focus should be on slow, controlled sit-down motion without the knee, hip, and foot turning inward.

John Fiore, PT
Sapphire Physical Therapy