Saturday, July 30, 2011

Is Knee Pain in Runners Really All About the Hips?

Today's question:

Are stronger hips the cure for a weak-hipped runner who has bad mechanics and is trying to beat knee pain?

The argument goes like this: If key muscles that stabilize the hip (when the foot strikes the ground while running) are weak, runners are prone to knee overuse injuries. That's because the thigh rotates too far inward, producing a knock-kneed stride.

So, armed with this knowledge, you strengthen your hips, and strengthen your hips, and ...

Nothing happens:
Researchers at Ohio University and the University of Delaware recently put the hip strengthening solution to the test. The study involved 20 uninjured women who exhibited abnormal adduction during running and single-leg squatting … Half of the subjects underwent a six-week training program of hip strengthening and single-leg squat technique instruction. The other half continued their normal training programs …

Despite improving hip strength and single-leg squat mechanics significantly, the strengthening program caused no change to the subjects’ running mechanics. Those who underwent the strengthening program continued to run just as knock-kneed as the women who had not.
Update: I had trouble finding the study online, but "Anonymous" below located it. Thanks! So here's a link for anyone wishing to look over the abstract.

What can be concluded from the study's findings?

Hip strengthening didn't fix bad running mechanics -- which suggests that hip strengthening didn't fix other bad mechanics either. So does that mean the underlying analysis that pinpoints weak hips as a problem is flawed? Not according to Fitzgerald:
These findings do not necessarily suggest that weak hip stabilizers are not the true underlying problem. More likely, they are evidence of the old principle, “Practice makes permanent.” While weak hips may cause certain runners to run with funky form in the first place, long-term repetition of this movement pattern gives it a life of its own. It becomes programmed into the motor cortex of the brain, so that even when the original cause (weak hips) is addressed, the pattern remains.

Further evidence in support of this conjecture comes from previous work by Irene Davis … Davis has shown that gait retraining -- a program of using biofeedback to teach better running mechanics -- does in fact correct internal thigh rotation and abnormal adduction, and it also helps alleviate knee pain.
I'm a bit suspicious of this "motor cortex programming" argument. It's not because I doubt that our brains can get in "ruts." I'm sure they can. In high school, I failed to make the baseball team after developing a hitch in my hitting swing from spending hours tossing small rocks in the air and batting them down the driveway, into the woods.

The trouble I have with this "motor cortex" reasoning is that it smacks too much of the ghost in the machine. You can't really prove or disprove it. Anyway, let's set aside that objection for the moment because Irene Davis apparently has shown that gait retraining does work -- and that naturally raises other questions.

Why strengthen the hip muscles at all? Why not just do the gait retraining? Does strengthening hip muscles have any beneficial effect? If it does, why was none of this effect captured in the Ohio University study? And what are the limitations of gait retraining?

Questions, questions. I'm always a bit suspicious of people who want to fix hurting knees by fixing something removed from the actual knees. (Strengthen your VMO/stretch your iliotibial band to bring your kneecap into alignment!) They often tend to be structuralists, who place an excessive importance on muscle imbalances and anatomical irregularities to explain away pain. What if the solution is simpler? If you have a weak, hurting knee, start on a program (long and boring, but it can be done) to strengthen the joint. It worked for me.

1 comment:


    A regular reader :)