Evaluation of functional leg-length discrepancy.
Leg-length discrepancy (LLD) may affect as much as 60 to 90 percent of the population, which should be of great concern to chiropractors. Whether functional or anatomical, the condition has profound effects on the body’s functional integrity and the biomechanics of the lower lumbar spine and sacroiliac joints.
Symptoms associated with LLD are diverse, but the most common is backache.1 Other symptoms include arthritis of the knee, psoasitis, arthritis of the hip, patellar tendinitis, patellofemoral pain syndrome, plantar fasciitis, medial tibial stress syndrome and metatarsalgia, iliotibial band syndrome with lateral knee pain, trochanteric bursitis, sacroiliac discomfort, Achilles tendinitis, and cuboid syndrome.2
Whenever you check a patient on the treatment table, whether prone or supine, errors of positioning are introduced and LLD is difficult to determine. Measurements of leg length obtained in a non-weight-bearing position tend to be unreliable.3
Many variables (such as subluxations in the pelvis and spine, and muscle imbalances) affect the alignment and relative positioning of the legs and feet when a patient is lying on a treatment or exam table. In a relaxed, upright posture, these confounding factors are no longer an issue. Then accurate clinical and radiographic determinations are possible and chiropractic care can proceed.4
Trouble with terminology
There is confusion surrounding this subject because DCs often use the term “short leg” in situations where the leg is not actually short. To clarify discussion, it is better to use the term “leg-length discrepancy” or “inequality” to describe asymmetrical leg lengths when the patient is standing and the spine is supported by the legs.
When you use this definition, all the confounding factors present when the patient is lying down (especially pelvic, lumbar, and cervical subluxations) won’t confuse your discussion of short legs. Because the only way a short leg will affect the spine and pelvis is when the patient is standing upright and during gait; that’s when the relative lengths of the legs can interfere with spinal function.
When evidence of LLD has been identified in the standing position, efficient treatment depends on identifying the source of the discrepancy. As the lower extremities provide the foundation and support for the pelvis during standing and walking, it is not surprising that they have a profound impact on the alignment of the pelvis and the spine.
A smooth and symmetrical gait has a significant effect on the pelvis, and is closely tied to proper vertebral function.5 During walking, there is a fine interplay between the movements of the feet, hips, and pelvis. Orthotics and shoe lifts can either improve or interfere with the proper functioning of the pelvis.
When a patient is standing upright, a short leg will cause several problems with postural alignment and the smooth function of the pelvis and spine. A difference in leg length results in an uneven foundation for the pelvis, causing postural shifts in response. Pelvic unleveling with a compensatory lumbar curve to the short side is a common reaction.6
The gait will alter in an attempt to make up for the difference, and eventually degenerative changes will be seen in the spine and hip joints.7,8 During gait, the foot and ankle complex pronates and there is a normal inward (medial) rotation of the entire lower extremity.
In people who have excessive or prolonged pronation, this twisting movement of the leg is accentuated. The increased rotational forces are transmitted up the leg into the pelvis, especially the sacroiliac (SI) joint.9 A chronic SI irritation then develops that can only be treated with a combination of chiropractic adjustments and orthotics.10
In addition, mechanoreceptors in the foot, ankle, and knee joints along with the muscle spindlesof the foot and lower leg muscles are responsible for support reflexes and a variety of automatic reflexive reactions.11 Difficulty in achieving or maintaining optimal postural alignment (e.g., excessive postural sway) is frequently caused either by inaccurate information sent by spindle sensors in chronically strained muscles or by joint mechanoreceptors in the asymmetrical lower extremities.12
Short leg etiology
Proper treatment of LLD depends on identifying the source of the short leg, as there are two possible causes and each requires a different treatment. Only one type of short leg is properly treated with a heel lift.
Functional short leg:
Definition: A difference in the alignment of the supporting structures between the ground and the, femur head. This is most commonly caused by excessive pronation on one side but may be due to knee valgus. Contrary to some definitions, a functional short leg cannot be caused by pelvic subluxations or lumbar muscle imbalances, as these problems do not change the length of the leg when the patient is standing.
Treatment: The first goal of treatment is to improve alignment and restore symmetry to the lower extremities. While adjustments and exercises may be useful, an orthotic with a pronation wedge under the heel is usually needed for long-term correction. Usually, the proper orthotic support for excessive pronation is all that is needed to balance functional LLD.
Anatomical short leg:
Definition: A difference in the size or length of the structures between the ground and the femur head. This is most often caused by growth asymmetry (which may be inherited), and sometimes by fracture or surgery.
Treatment: When an anatomical difference in leg length interferes with balanced alignment of the pelvis and spine, it can be treated with a lift under the heel. Since the body is able to tolerate some asymmetry (studies indicate that 5 to 6 mm is the limit), an exact correction is not needed. A slight under-correction (to within about 3 mm) can ensure a good response and avoid negative reactions. You can add a heel lift to a custom-made orthotic to ensure proper foot and ankle biomechanics. If the amount of lift needed exceeds 6 mm, the additional lift should be built onto the shoe.
Because correct treatment is based on the cause of a short leg, it is essential to determine the reason for the difference. The cause of LLD cannot be inferred from X-rays, measurements, tests on an exam table, or from the patient’s history.
The only basis for deciding whether to use an orthotic or a heel lift to treat a short leg is the clinical weight-bearing postural examination of the pelvis and lower extremities, as follows:
- Position the patient in bare (or stocking) feet on an unyielding level surface.
- Ask the patient to stand in a relaxed, normal, upright posture.
- Palpate the iliac crests and the lumbar spine, looking for unleveling and compensatory curvature.
- If either is present, check to see if the greater trochanters and knee joints are level.
- If not, evaluate the knee alignment for valgus, and the feet for asymmetrical hyperpronation.
- If you find evidence of a functional short leg, try to temporarily correct it while palpating the pelvis. First, ask 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 a normal relaxed If the pelvis dips down or rotates forward on the side of greater foot pronation, this demonstrates the effect of the foot imbalance on the pelvis and lumbar spine.
- If there is no significant asymmetry in alignment, then the difference is anatomical.
Once the cause—either functional or anatomical—of the short leg is identified, the treatment has also been determined. When a heel lift is planned for a patient with an anatomical short leg, obtain an accurate X-ray measurement of the true difference in leg length. Take a standing view of the femur heads without projectional or magnification distortion.
To decide whether to use an orthotic or a heel lift to treat a short leg, conduct a clinical weight-bearing postural examination of the pelvis and lower extremities. If a functional cause for the short leg is found, then an orthotic alone is needed. If there are no clinical findings to support a functional short leg, then (by exclusion) an anatomical short leg is present, and a heel lift is needed.
Excessive stress on the musculoskeletal system from imbalances in the lower extremities can destabilize the spine and pelvis. If any part of the lower extremity is not functioning correctly during the stance phase of gait, abnormal strain is transmitted to the pelvis with every step.
Correction of a functional short leg is just one of the ways proper orthotic support can help alleviate many chronic spinal conditions.
John K. Hyland, DC, DaCBr, DaBCO, CSCS, is a 1980 cum laude graduate of Logan College of Chiropractic. He is also a certified strength and conditioning specialist (CSCS). a popular speaker, Hyland is a postgraduate lecturer for several chiropractic colleges and a frequent contributor to chiropractic publications. He can be contacted at firstname.lastname@example.org.
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