UNC researchers ask: Can a short leg cause knee or hip pain?

Dr. Joanne Jordan

Yvonne Golightly, PT, PhD, and Joanne Jordan, MD, MPH, have studied this surprisingly common condition and recently received a $3.5 million grant from the Centers for Disease Control and Prevention to continue their research.

Golightly, postdoctoral fellow and physical therapist at the UNC Thurston Arthritis Research Center, and Jordan, Thurston Center director, distinguished professor of medicine in the UNC School of Medicine and adjunct professor of epidemiology in UNC Gillings School of Global Public Health, examined about 1,500 Johnston County, N.C., residents ages 45 and older. In the 1990s, they measured participants’ legs with a tape measure and, using X-rays, checked their knees and hips for osteoarthritis. Then, about six years later, the researchers conducted the same measurements.

The findings are consistent with another study, published in 2010 in Annals of Internal Medicine, that examined 3,026 people between the ages of 50 and 79. That study, too, found that participants with at least a one-centimeter difference in leg length, based on X-ray measurements, were more likely to have osteoarthritis in the knee.

As much as 70 percent of people have legs that are slightly different in length. Usually, the discrepancy is small – less than a centimeter – and it probably doesn’t make a difference to a person’s health.

Researchers still disagree about exactly how prevalent leg length inequality is or how much of an inequality is necessary to cause problems, Golightly said. But a study published in 2005 in the journal Chiropractic & Osteopathy suggests that about 20 percent of people may have a leg-length inequality of one centimeter (0.4 inch) or more.

Short-leg syndrome can begin in childhood as a result of an injury, infection or a difference in growth rates between the legs. Adults also can develop an inequality because of surgery, such as hip replacement. Leg asymmetry subtly can change a person’s gait, altering the forces acting on the legs as the person walks or runs.

Other researchers have suggested that short-leg syndrome may increase the risk of lower back pain, stress fractures and running injuries. However, Golightly said, researchers haven’t yet conducted large studies to evaluate those hypotheses over time, so it is hard to know for sure what role the syndrome plays in those conditions.

If you suspect you have a short leg

A difference in leg length of an inch or less can be difficult to detect on your own, so if you suffer from knee or hip pain, talk to your physician or physical therapist about leg-length inequality.

The length of your legs is easy to assess using a simple tape measure. Your doctor also may ask for an X-ray, as that is the most accurate and reliable method of measurement.

And there’s good news about leg-length inequality: “It is easy to treat for most individuals,” Golightly said.

If you are an adult, your doctor likely will ask you to wear a lift, which can be inserted into the shoe or added to the sole of the shoe to effectively increase the length of the shorter leg. A physical therapist also can help you stretch tight muscles and strengthen muscles that may be weak as a result of the inequality.

For children with significant leg-length inequalities, doctors can use surgical techniques to lengthen the shorter limb or shorten or slow down the growth of the longer leg, so that eventually the legs match in length.

UNC Gillings School of Global Public Health contact: Ramona DuBose, director of communications, (919) 966-7467 or ramona_dubose@unc.edu. Much of this original article was written by Sara Peach for UNC Health Care.