July 3, 2011

Patellofemoral Pain Syndrome (Runner's Knee) - The Q Angle And How It Affects The VMO

If you were to draw a straight line from the ground up, starting at the floor and passing directly through the middle of your kneecap, you’d probably notice that as you follow that line upwards, by the time you got to your hip, the angle in which your femur (upper leg bone) travels in is not of a direct north and south nature. The angle of the top of your femur in relation where it attaches to your kneecap is known as the Q angle (quadriceps angle). This angle has direct implications on muscle recruitment, and development, and is the culprit as to why most women (and men, although it is less common) who have patellofemoral pain syndrome, developed it in the first place.

Some literature suggests that an estimated 20,000 teenage girls in the States suffer knee injuries each year. Is this simply a coincidence? Well, considering that women generally have a greater Q angle as a result of having relatively wider hips than men, for obvious reproductive reasons, it’s likely not a coincidence at all and here’s why.

Patellofemoral pain syndrome is the result of chronic overuse which can be caused by many different factors, all of which can generally be traced back to the Q angle. Imbalanced development between the vastus lateralis (larger of the quad muscles on the outside of the thigh) and vastus medialis oblique (VMO, relatively smaller quad muscle on the inside of the knee) may result in divergent tracking of the patella (kneecap) along the femoral condyles (bottom of the upper leg bone), and this imbalance can (and in most cases, does) stem from ones anthropometry (Q angle in this case).

The VMO is responsible for making sure the kneecap is tracking properly while flexion and/or extension is taking place at the knee joint. A problem arises when the vastus lateralis is relatively stronger than the VMO, it will pull laterally (to the side away from the body) on the kneecap. If this imbalance is left untrained, it will gradually become worse, possibly leading to the development of patellofemoral pain syndrome.

How is the Q angle directly involved in this? Well, if the hips are relatively wide, which is generally the case with most women for reproductive purposes as mentioned above, standing in a natural, relaxed state, results in the feet being relatively closer to each other in relation to where the leg starts at the hip joint. This stance places the VMO in a position of disadvantage, resulting in imbalanced development due to underuse.

Because of this, activities like walking, jogging, running, and nearly every movement required in sport, will favor the recruitment of the synergistic muscles at the expense of the VMO. Combine this with the fact that the VMO is most active through the first, and last, 15 degrees of knee extension, and it’s apparent why knee pain as a result of overuse occurs in the first place.

A relatively weak VMO is probably the most common muscular imbalance that there is, and is visibly apparent because if the VMO is weak, the knee will gravitate towards the midline of the body during functional movement (squatting, and in extreme cases it can be seen by just walking). This has downstream effects because if the knee is gravitating towards the midline of the body, you have to wonder what effect will this have at the hip and ankle joints?

In terms of the hips the muscles responsible for providing lateral stability, and external rotation, are in a position of disadvantage, and at the ankle the foot will pronate and flatten its arch. This feeds the cycle, and things generally get worse from there unless properly addressed.

While the metrics of your bones are out of your control, creating a structurally sound body is not. Therefore, knowing and understanding the effect that your anthropometry has on your development is of paramount importance, and should have direct implications in terms of program development, exercise selection, and how exercises are to be performed to correct imbalanced development, and prevent it from getting worse.

If you have any questions about patellofemoral pain syndrome, or the Q angle, feel free to contact me at ben@paramounttraining.ca. I'm available for online consulting and personalized program design, as well as one on one training if you are located in the Greater Toronto Area (GTA).

1 comment:

  1. Great article. Very helpful. Thanks for posting! :)