If you suffer from a baffling series of overuse running injuries, there often is a root cause, other than the usual overtraining, bad shoes, too much racing syndrome. One of the most common conditions that plague runners is something called leg-length discrepancies. In short, the lengths of your legs are unequal. One is longer than the other. For most people, this isn’t necessarily a problem. But for a runner it often is because of the repeated stress that is placed on the lower legs. If one leg is shorter (or longer), the stress is not equally distributed and injuries are often the result.
If this sounds like an extreme condition, you might be surprised to learn that 60-90 percent of the world’s population has a leg-length discrepancy. And for runners, leg-length discrepancies are the third most common cause of overuse injuries, whether the injured runner realizes it or not.
There are two types of leg-length discrepancies: congenital and acquired. Congenital is the more common of the two and it simply means you were born with legs (and often, arms) of unequal length. One leg is shorter than the other. The differences are often very slight, usually less than a quarter of an inch. It may not even be detectable and you probably have never even noticed it because as you develop, the brain picks up this leg-length discrepancy and over the years adapts to it. If the difference is minimal, the body might adapt by tilting one shoulder over very slightly to the shorter side to compensate.
But, over time, runners will notice the difference. Maybe not perceptibly at first, but a difference greater than a quarter of an inch will eventually take its toll and since the body tries to compensate, all sorts of structural imbalances and injuries can result.
The four most common injuries related to leg-length discrepancies are generally but not limited to (1) illiotibial band syndrome (pain or soreness on the outside part of the knee); (2) piriformis pain located in the area of the butt; (3) hip soreness and (4) low back pain which is the most common symptom. There are certainly other runners injuries that are related to leg-length differences.
What can you do? First, the differences in your legs length must be properly diagnosed by a sports-medicine professional who will measure both legs and determine whether a discrepancy actually exists. If so, the measurements will reveal the exact differences and further tests—often a simple gait analysis–will reveal whether this is the root cause of the injuries.