Keys To Recognizing And Treating Limb Length Discrepancy

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Author(s): 
Joseph C. D’Amico, DPM, DABPO

   As a one-limb single plane deformity, limb length discrepancy is capable of producing a number of compensatory changes that are ineffective in correcting the original deformity and may magnify the problem throughout all body planes. The nature of compensation is individually unique and determined by age, site, severity, flexibility, body type, weight and other variables.

A Closer Look At The Clinical Significance Of Limb Asymmetry

Since limb length asymmetry is such a common situation, we often regard it as normal. However, nothing could be further from the truth.

   The musculoskeletal system is built to function most efficiently when neuromotor control is intact and there is adequate but not excessive joint ranges of motion in an aligned, symmetrical lower extremity complex. Since the foot represents the foundation for this complex, it is critical that it be properly aligned and function in the appropriate symmetrical, adaptive or stabilizing manner at each stage of the gait cycle.14,26,27 According to Von Baeyer’s 1898 “Closed Chain of Links,” postulate defects or deficiencies in one segment affect the entire chain.20

   Perhaps the most obvious effects of LLD are on posture. Limbs with length discrepancies are obviously less efficient during gait but there are increased demands on postural musculature in an imbalanced musculoskeletal system during stance as well.1

   Limb length discrepancy is reportedly the third most common cause for running injuries, most often occurring below the hip and appearing first on the longer side.28,29 Researchers have implicated asymmetrical pronation producing a functional limb length discrepancy as a causative factor in sciatica.30 As I previously noted, the longer limb is subject to osteoarthritis of the hip and increased risk of stress fractures while the shorter limb has a higher incidence of knee pain and degenerative joint disease.

Essential Insights On Symptomatology

The most common symptoms associated with limb length discrepancy are low back pain, which usually appears on the longer side first.31-33 Other complications include sacroiliac malalignment, functional scoliosis, sciatica, disc herniation, posterior vertebral facet impingement, hip and knee pain as well as degenerative joint disease, especially on the longer side. Additional findings include: piriformis and iliotibial band syndromes; greater trochanteric bursitis; plantar fasciitis; posterior tibial stress syndrome; patellofemoral pain syndrome; hallux valgus; altered gait patterns; pelvic obliquity toward the shorter limb; contracture of the Achilles tendon on the short limb; and short limb metatarsalgia.1,17,21,34-38

   In the sports participant, chronic unilateral overuse injuries that persist despite appropriate care sometimes diffuse and clinicians sometimes may falsely attribute them to LLD. Even “minor” discrepancies in runners may produce symptomatology due to the “rule of three” theory, which states that running forces average three times body weight — three times that required for normal walking — for which the body will compensate at the weakest link in the musculoskeletal chain.21

Who To Treat

The orthopedic literature is confusing regarding the amount of discrepancy adults can tolerate without treatment. Treatment often depends on whether symptoms are present and the degree of musculoskeletal malalignment present. However, an incidental finding of an LLD in an athlete might well be worth equalizing in order to improve symmetry, efficiency and performance as well as to prevent injury. Subotnick states that one should treat discrepancies of as little as 6 mm in an athlete.25

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Stanley Beekmansays: June 8, 2014 at 11:23 pm

Great article!

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