“If I am constantly getting injured on one side, that must mean that I have a leg-length discrepancy, right?”

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Significant leg-length discrepancies are not that common. Frequently, an athlete who is lying flat on a table, will be evaluated by an observer standing at the foot of the table. The observer takes the athlete’s feet in his or her hands, presses the ankles together, “eyeballs” the soles of the feet, and finally declares, “Yep! Your left ankle bone is a full half-inch below your right one, pal! Your left leg definitely is longer.” Then the athlete goes out and gets a half-inch lift for the right shoe so that both legs can be even. This apparent leg-length discrepancy probably is caused NOT by a leg bone that is longer, but by an imbalance in the muscles and tendons of the pelvis, the foundation of the body. And the source of this imbalance might surprise you. A tight hamstring on one side can jack the other side of the pelvis up. A tight iliotibial band on one side could jack the other side of the pelvis up. 

The imbalance is common in people who do one thing in the same way all the time, such as a runner who sprints around a track in one direction day after day. Tennis players who develop their upper bodies on one side because they swing their rackets with their dominant hands can experience imbalance in the muscles that affect the pelvis. When the pelvic region—hips and trunk—is free-floating and flexible, an apparent leg-length discrepancy may “mysteriously” disappear.