Self-diagnose Your Running Knee Injuries

Last week, we talked about how to watch for hip drop, a common problem with running form.  Its primary cause is usually weak hip abductor muscles, but even with strong hip abductors, you can sometimes suffer from faulty biomechanics.  In other words, even if you are strong enough, your stride may still be “broken.”

As we’ve seen before, one of the most well-identified problems with many runners’ form is excessive hip adduction—when the upper leg slants inwards towards the center of the body during the stance phase.  A good bit of research has showed that excessive hip adduction is linked to injuries in the knee,¹ IT band,² and more.  What’s worse, women seem to have a much higher incidence of excessive hip adduction than men do,³ possibly accounting for some of the “gender gap” in injuries (while the rate of participation in running between genders is fairly even, women make up 54% of injured runners and 60% of runners with knee injuries).⁴

While checking for hip drop due to weak hip abductor muscles or poor muscle firing patterns can help, it’s entirely possible to have poor hip mechanics without a perceptible hip drop at the waist.

Evaluating hip mechanics

While researchers use high-tech 3D cameras in gait laboratories to measure hip adduction, those tools aren’t available to the average runner.  Another “field test” I particularly like for evaluating hip mechanics is checking leg crossover.

When running with “good” form and mechanics, your footstrikes should land right on a straight line.  If your hip adducts excessively, one leg will “cross over” the other, and your foot will strike across the centerline of your body.  For example, if your right hip’s mechanics are faulty, your right leg may cross over to the left side of your body as your foot hits the ground.  Because you are effectively putting your weight further towards the left side of your body, this can counteract the hip drop you might otherwise see, thus obscuring your problem.

Now, leg crossover is far from a perfect measure of hip mechanics:  sometimes, even though your foot lands in the right place, your knee will buckle inwards, creating excessive hip adduction and knee internal rotation.  Checking your footstrike won’t help in this case.  However, since you won’t be supporting the opposite side of your body as strongly, you may be able to observe hip drop in this case.

How to check for leg crossover

Anyways, moving on to how to check for leg crossover.  If you have access to a video camera or a treadmill with a mirror in front of it, you might be able to observe it directly.  But since catching exactly where the foot falls in a third of a second or less can be tricky, I prefer to measure it indirectly by observing footprints.

The sight of a runner’s footprints on wet sand or freshly fallen snow can give you some clues about his or her hip mechanics by observing how much the left and right foot overlap.  Snow and wet sand aren’t easy to come by, but you can make a small puddle of water with a garden hose on a stretch of dry pavement or asphalt, then run through it and continue running in a straight line.  Then, looking back at your footprints, you can determine whether your legs are crossing over the centerline of your body.

What leg crossover looks like

The image above illustrates the different scenarios you might see in your shoeprints.  On the left is what you’d like to see: a balanced stride where the left and right footfalls overlap by about a third of a shoe’s width.  In the middle is a mild crossover pattern; in this case, the left leg is crossing over the centerline of the body and landing on the right side of the body.

Now, you are unlikely to have a thin line on which to run, so in real life, you might need to do some detective work to figure out which leg is crossing over if you see that your footfalls are overlapping too much.  Usually you can tell by running along a line (either painted on the road, on the track, or on an athletic field) and glancing down to see which is the offending leg.

Finally, on the right is a “wide stance” which is uncommon but does occur.  There’s no evidence to indicate that this is injurious or undesirable, but it’s something to take note of nonetheless.

What to do if you do suffer from leg crossover

If you do have leg crossover, what’s to be done? While hip strength is never a bad idea, in my experience, leg crossover is more likely to be caused by muscle firing patterns than weak glutes (unlike hip drop).

The easiest way to correct crossover is to practice running with good form—i.e. no crossover—for short stretches of time by running on a track, football field, or soccer field and trying to keep your footfalls even and on one of the painted lines.  Avoid doing this on the roads if you can, since you ought to be looking out for cars instead! Continue to work on your form in small doses and develop strong mental cues that remind you of how to run with good form. You can then transfer these mental cues to your normal run for longer and longer stretches. Eventually, you’ll be able to run an entire run without reverting to excessive leg crossover and stave off knee injuries.

In sum, while leg crossover is not a perfect metric for excessive hip adduction, it’s another good “field test” you can do without any expensive equipment or specialized facilities.  And it’s a pretty common problem too.  Fortunately, with a little practice and a few attentive miles on the track or soccer field, you can keep it under control and hopefully reduce your risk of injury.  Retraining your running form is a slow process, of course, so don’t be discouraged if it takes a while to straighten out your legs.