by John Danchik, DC, FICC, CCSP
The presence of a short leg might initially be suspected from a patient’s clinical exam, spinal X-rays, or from a history of recurrent subluxations. The first step is an accurate examination to determine the amount of difference and the influence this discrepancy has on the patient’s spine and gait. Next, the source of the inequality must be determined so that the correct treatment can be provided. And finally, the treatment must be evaluated to determine if it has sufficiently addressed the problem.
This process cannot be performed without examining the patient in the upright, weightbearing position. Whenever a patient is checked on the treatment table, whether prone or supine, errors of positioning are introduced (and are very difficult to exclude). Measurements of leg length discrepancy obtained in non-weightbearing positions have been found to be very unreliable.1 In the upright posture, these errors and confusions are no longer a factor. Accurate clinical and radiographic determinations are then possible,2 and effective Chiropractic care can proceed. Since the lower extremities provide the foundation and support for the pelvis during standing and walking, it is not surprising that they can have a profound effect on the alignment of the pelvis (and the spine, as well).
Effects and Causes
When one leg is shorter, there is often pelvic unleveling with a compensatory lumbar curve to the short side.3 Gait will be altered somewhat in an attempt to make up for the difference, and eventually, specific degenerative changes will be seen in the spine4 and hip joints.5 Studies have found that a difference in leg length (measured while standing) between 5mm to 9 mm or more results in a higher incidence of low back pain.6,7 Athletes and those who spend a lot of time on their feet could develop chronic symptoms with just 3 mm of discrepancy.8 There are two possible causes of a short leg, and each cause needs different treatment. Therefore, a successful outcome is dependent upon differentiating whether a patient has an anatomical asymmetry or a functional imbalance.
An anatomical short leg is caused by a difference in the length and/or size of the structures between the femur head and the ground. This is sometimes found after a fracture or surgery, but it is most often the result of asymmetrical growth. A functional short leg develops secondary to a difference in the supporting structural alignment between the femur head and the ground. The most common cause is excessive pronation on one side, but knee valgus could also be a causative factor. Pelvic subluxations and/or lumbar muscle imbalances cannot be the cause, since these problems do not alter leg length while standing or walking.
The first step in treatment of a patient with a short leg is the clinical weight-bearing postural examination of the pelvis and lower extremities. Start by positioning the patient in bare (or stocking) feet on an unyielding, level surface. Tell the patient to stand relaxed in a “normal upright posture.”9 Now palpate the iliac crests and the lumbar spine to determine if there is any pelvic unleveling and a compensatory lateral curvature. If either of these is found, see if the greater trochanters and knee joints are level, and evaluate the knee alignment for valgus and the feet for asymmetrical hyperpronation. If there is evidence of a functional short leg, check to see if the pelvis and spinal imbalances can be temporarily corrected. This is done by asking the patient to roll onto the outsides of both feet. As you palpate the levels of the iliac crests and greater trochanters, ask the patient to relax and return to normal, relaxed stance. If the pelvis dips down or rotates forward on the side of greater foot pronation, this shows the effect of the foot imbalance on the pelvis and lumbar spine. A lack of significant asymmetry in the lower extremity alignment reveals the difference to be anatomical.
The only acceptable method for obtaining an exact measurement of leg length discrepancy is with properly positioned standing X-ray images.10 To do this, we must limit sources of projectional distortion and magnification distortion, while carefully controlling equipment alignment and patient positioning. This entails the use of either an AP lumbopelvis view taken at a distance of 72 inches or 80 inches (instead of 40 inches) or a tightly collimated spot view of the femur heads from 40 inches. With both of these methods, the patient must be standing in bare feet on an unyielding, level surface. Body weight is borne equally through both legs, with the knees extended. Heels are placed directly under the femur heads (the “parallelogram” stance), which ensures accurate measurements even with lateral displacement of the pelvis. All X-ray equipment components must be installed level and square, especially the bucky. The film must be placed along the bottom of the cassette, and the cassette must rest squarely in the bucky. If all factors are controlled, then accurate measurements of true femur head heights can be obtained from the standing films, and the effect of any discrepancy on the spine and pelvis can be determined.
When there is evidence of a difference in lower extremity alignment (such as excessive pronation), the most effective treatment is to provide symmetrical support. This is accomplished by supplying custom-made corrective orthotics for both feet. It is very important to recognize the functional short leg, since providing a lift instead of an orthotic is likely to perpetuate the associated sacroiliac subluxations.11 There is no reliable information on the radiographs to make this differentiation—it is only the standing postural exam with careful evaluation of lower extremity alignment that permits this determination. If there is any doubt, the safest approach is to fit the patient with custom-made orthotics, initially. If there is a persisting leg length discrepancy after wearing the orthotics for several weeks and receiving Chiropractic adjustments, a heel lift can then easily be added to the orthotic for complete correction.
When an anatomical difference in leg length affects the alignment of the pelvis and spine, Chiropractic care should include the recommendation of an appropriate amount of lift under the heel. Since some asymmetry is tolerated by the body (most good studies find that about 5 mm is the limit),12 an exact correction of the difference measured at the femur heads is not needed. The exception to this might be athletes (such as long-distance runners) who spend many hours a day exercising and competing on their feet. For most patients, undercorrection (to within about 3 mm) is the best way to ensure a good response while avoiding any negative reactions. If the amount of lift needed exceeds 6 mm (the difference measured at the femur heads is more than 10 mm), the additional lift must be built onto the shoe, since a lift in excess of 6 mm will push the foot out of most shoes. This is done by adding half of the heel lift amount to the sole of the shoe, so the foot is not excessively plantarflexed during stance and gait.
Once a patient with a short leg has been properly examined, the source of the lower extremity shortening can be identified, and effective treatment can be provided. In many cases, orthotic support for foot pronation, knee rotation, or femur angulation is needed. Those few patients with a true anatomical leg length discrepancy will need to be supplied with an appropriate lift. The additional time required to determine the source of the short leg will be repaid in more effective Chiropractic care and adjustments that last.
About the Author
Dr. John J. Danchik is the seventh inductee to the American Chiropractic Association Sports Hall of Fame. He was the chairperson of the United States Olympic Committee’s Sports Medicine Physician Selection Program. He lectures extensively in the United States and abroad on current trends in sports chiropractic and rehabilitation. Dr. Danchik has served as an associate editor to the Journal of the Neuromusculoskeletal System and the Journal of Chiropractic Sports Injuries and Rehabilitation. He is in private practice in Massachusetts.
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