Unequal leg length is so common in the general population that many consider it normal. Though structured with bilateral symmetry, every human body presents some degree of asymmetry. Minor differences in leg lengths will not affect most sedentary people because they do not have to adapt to much biomechanical stress. Runners, on the other hand, are forced to absorb five to seven times their body weight with each strike of the heel.

Running is a sport that requires equal movement, strength and impact on both sides of the body. Running on a short leg is comparable to running repeatedly on a curved road. Over a few miles, the difference is hardly noticeable. However, over the course of days, weeks, months and years, altered biomechanics and the resulting stress will exceed the body's capacity to repair and adapt. This is when the injuries occur. Common injuries associated with leg length discrepancies include low back pain, sciatica, hip pain, knee problems, IT Band Syndrome, chronic muscle strain and tendonitis.

There are two classifications of leg length differences: anatomical and functional. An anatomical short leg is one in which there is a measurable difference in bone length between the two legs. This may be due to fractures, knee or hip degeneration, deformities or unequal growth rates. A heel lift utilized on the "short" side will help compensate for this difference.

By contrast, a functional short leg appears shorter, but measures the same length as the other leg. The two most common causes are overpronation of the foot and backward rotation (misalignment) of the pelvis. Pronation can be corrected by strengthening the ankle joint with an orthotic or surgical tubing and resistive exercises. Spinal manipulation will correct misalignment of the hip. Manipulation should be performed in conjunction with stretching of the hamstrings, quadriceps, gluteus and hip flexor muscles to achieve lasting results. A heel lift is not the proper solution to a functional short leg. This will serve only to reinforce the altered biomechanics and resulting stress.

One of the simplest ways to determine the classification of a short leg is to measure both legs. Measure from the front of the pelvis (anterior superior iliac spine) to the inside ankle bone (medial malleolus) and compare. Many runners have been diagnosed with unequal leg lengths but not told whether the discrepancy was anatomical or functional. This is an incomplete diagnosis and the resulting treatment may be inappropriate or inadequate.

Running injuries are greatly influenced by unequal leg lengths. If you have suffered from injuries that are chronic or recurrent, have your leg lengths checked!

With more than 35 years of competitive running and over 60 road race victories between them, Dr. Ronald S. Kulik and Dr. Neil P. McLaughlin are among the leading National Capital Area physicians who specialize in the drug-less, nonsurgical treatment of athletes and sports related injuries. Dr. Kulik and Dr. McLaughlin are avid participants in the Reston Runners as well as members of the ACA and VCA Council on Sports Injuries and Physical Fitness. Drs.Kulik and McLaughlin practice at the Commonwealth Chiropractic Center of Reston, where they treat many of the area's top runners. Questions or comments should be sent to 11319 Sunset Hills Road, Reston, VA, 22091. (703)742- 7856