A new study reveals the limitations of strengthening the hips to prevent knee injuries.
Written by: Matt Fitzgerald
The hip joint—or rather, certain muscles attached to it—have been under scrutiny lately in the running world. Recent research has suggested that weakness in key muscles that stabilize the hip during the ground contact phase of the running stride predisposes runners to overuse injuries, particularly at the knee. Runners with weak hip stabilizers appear to have tendencies to rotate the thigh inward and to excessively adduct the hip (i.e. run knock-kneed) to create stability to compensate for the weakness of the hip stabilizers. These maladaptive movement patterns put strain on the knee, and over time an injury emerges.
In short, the theory is that muscle weakness creates bad form, which in turn creates an injury. Since the root of the problem is muscle weakness, it stands to reason that strengthening the hip stabilizers might correct internal rotation of the thigh and excessive adduction and prevent knee injuries. However, the solution might not be so simple.
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 (a test that physical therapists use to diagnose weak hip stabilizers). 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. The running mechanics of all 20 subjects were then reexamined.
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.
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, who was one of the researchers involved in the present study. 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.
So, if you’ve had knee injuries, should you forget about strengthening your hips and instead concentrate on improving your form? No. Strengthening your hips will only make it easier to correct your form, and there is some evidence that strengthening the hips helps runners overcome knee pain even without causing a measurable change in running form.[sig:MattFitzgerald]