CHAPEL HILL - Legs of unequal length can contribute to osteoarthritis as well as knee and hip pain, according to a first-of-its-kind University of North Carolina at Chapel Hill School of Medicine study.
By prescribing special shoes or other adjustments and exercises to make up the difference in the large number of arthritis patients who have legs of different length, doctors might be able to prevent or slow progression of the degenerative, sometimes crippling, bone condition, researchers say.
"We are very excited about our findings because in a sense they are so simple," said Dr. Joanne M. Jordan, research assistant professor of medicine at the UNC-CH's Thurston Arthritis Research Center. "They are clinically relevant because we and others should be able to do something really useful for millions of people now and in the future. Several major risk factors for osteoarthritis, such as aging, cannot be avoided, but this is an important one we can do something about."
Jordan presented results of the first large population-based study of the link between leg length and knee and hip pain Wednesday (Nov. 11) at an American College of Rheumatology meeting in San Diego.
The research involved measuring the length of both legs from the hip to the inner ankle in 2,987 people participating in UNC-CH's continuing Johnston County (N.C.) Osteoarthritis Project. Investigators compared their measurements with reported levels of pain from hip and knee osteoarthritis and results of physical examinations, extensive interviews and X-rays.
Jordan and colleagues found knee and hip osteoarthritis to be strongly associated with leg length discrepancies of two centimeters or more. They discovered that, overall, 9 percent of the study population had legs of different lengths, significantly more than they expected.
"While 5 percent of people without knee osteoarthtritis showed differences in how long their legs were, a full 16 percent of those with severe knee osteoarthritis had leg length discrepancies," she said. "The figure was almost 20 percent for people who had hip arthritis."
After controlling for such factors as age, gender, obesity, race and previous injuries, researchers found having one leg two or more centimeters shorter than the other increased the risk of knee arthritis by about 70 percent and the risk of hip arthritis by up to 50 percent. The condition also increased the risk of knee pain almost 50 percent, but had only modest effects on hip pain, they found.
"Measuring leg length is something that primary care physicians and even rheumatologists normally don't do, but this work shows that they should start doing it routinely in patients complaining of knee or hip pain," Jordan said. "The beauty of it is that it is simple, non-invasive, costs nothing and could help a lot of people."
When doctors find a leg length discrepancy, they can refer patients to physical therapists who correct non-complicated cases through orthotic devices such as special shoes, she said. The result can be dramatic pain relief.
Co-authors of Jordan's paper include Dr. Alfredo Salazar, visiting professor of rheumatology; Dr. Jordan Renner, associate professor of radiology; and biostatistics doctoral student Gheorghe Luta, all at UNC-CH. Others are Drs. Marc Hochberg of the University of Maryland, and Charles Helmick at the Centers for Disease Control and Prevention. The CDC and National Institute of Arthritis, Musculoskeletal and Skin Diseases supported the research.
"It is absolutely clear that arthritis will become an increasing problem as baby boomers age," Jordan said. "We are already seeing it. Several studies have projected that by the year 2020, the number of people suffering from arthritis in this country will increase from 40 million to about 60 million."