Leg Length Discrepancy

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Definition

Leg length discrepancy, or anisomelia, is defined as a condition in which the paired lower extremity limbs have a noticeably unequal length.

Classification of Leg Length Discrepancy (LLD)

Structural (SLLD) or anatomical: Differences in leg length resulting from inequalities in bony structure.

Functional (FLLD) or apparent: Unilateral asymmetry of the lower extremity without any concomitant shortening of the osseous components of the lower limb.

There are three types1,2 of limb length discrepancy inequality (LLI) also called leg length discrepancy.
- Anatomical1,2; structural limb length inequality. It’s a physical (osseous) shortening of one lower limb between the trochanter femoral major and the ankle mortise.
- Functional1,2; non-structural shortening. It is a unilateral asymmetry of the lower extremity without any shortening of the osseous components of the lower limb.*
- Environmental1; it’s only significant for a small number of high-level athletes or a specialized workforce population. An example: accumulation of forces during running when a runner consistently trains on 1 side of a crowned road.
 Environmental LLI can easily be solved by asking the runner to run <g class="gr_ gr_393 gr-alert gr_gramm Grammar multiReplace" id="393" data-gr-id="393">in</g> the opposite side then he usually runs. Environmental LLI is often considered as a functional LLI.
• A functional inequality may occur at any level of the lower extremity from the most superior aspect of the ilium to the most inferior aspect of the foot. Different causes may lead to a functional inequality: foot mechanics, adaptive shortening of soft tissues, joint contractures, ligamentous laxity and axial malalignments
.

Epidemiology

Prevalence of LLD is a topic in recent literature that evokes heavy discussion. Little agreement exists regarding the degree of LLD that is clinically significant to treat, with values ranging from 3 to 60 mm. Some authors have tried to determine a significant LDD by quantification, others by a significant discrepancy in functional outcomes. These values are found in the review by Burke Gurney 2002 Gait and posture. Prevalence rates for leg length difference often lack crucial information regarding demographics, examiner experience, methods to recruit patients, methods used to detect leg inequality and yet it is often cited and used by other authors.

Etiology 

• Developmental abnormalities
• Fracture
• Trauma to the epiphyseal endplate prior to skeletal maturity
• Degenerative disorders
• Legg-calvé- Perthes disease
• Cancer or neoplastic changes
• Infections

Functional:

•  Shortening of soft tissues
•  Joint contractures
•  Ligamentous laxity
•  Axial malalignments
•  Foot biomechanics (such as excessive ankle pronation)
  

Characteristics/Clinical Presentation

In concordance with the classification of LLD, the characteristics can be divided into two categories:
Functional limitations, including gait and balance and
The role of LLD standing posture/ balance.

Check for specific compensation used by the patient to level out the difference in height.:
- Pronation in the ankle of the longer leg
- Supination or plantar flexion of the shorter leg
- Knee and hip extension of the shorter or flexion in the longer leg
- If the leg is left uncompensated, the anterior and posterior iliac spine on the side of the short leg can be lower which may result in a sacral base and/or scoliosis.
- Increased muscle activity in several muscle groups
The role of LLD on walking:
- Gait asymmetries throughout the kinetic chain
- Increased vertical displacement of mass resulting in increased energy consumption.
o Compensatory mechanisms for this: calcaneal eversion, knee extension, toe walking, circumduction, hip or knee flexion (steppage gait)
- Decreased stance time and stride length in the shorter leg
- Decreased walking velocity, increased walking cadence
The role of LLD on running: in running is different from walking, as are the effect of LLD. In running, the vertical oscillation is greater and there is no double support so weight is not shared between legs. The stance phase is only 30% in running in walking. This results in stress the lower extremity that is three times that of walking. Evidence is conflicting about the effect of <g class="gr_ gr_439 gr-alert gr_gramm Punctuation only-ins replaceWithoutSep" id="439" data-gr-id="439">running</g> but it is suggested that the effect is also augmented threefold.

Associated musculoskeletal <g class="gr_ gr_394 gr-alert gr_gramm Punctuation multiReplace" id="394" data-gr-id="394">disorders :</g>
Low back pain: Literature is very ambiguous. LLD appears to affect the lumbar spine, at least in part, by creating a lumbar scoliosis. It has been shown that LLD leads to pelvic obliquity <g class="gr_ gr_400 gr-alert gr_gramm Grammar multiReplace" id="400" data-gr-id="400">on</g> the frontal plane inducing a scoliosis. (Gurney) .
Lumbosacral facet joint angles appear to be smaller on the short side, it is hypothesized that <g class="gr_ gr_407 gr-alert gr_gramm Grammar only-ins doubleReplace replaceWithoutSep" id="407" data-gr-id="407">asymmetry</g> of joint angles <g class="gr_ gr_405 gr-alert gr_gramm Grammar multiReplace" id="405" data-gr-id="405">predispose</g> patients to osteoarthritic changes in lumbosacral joints. (Giles)
Further research will conclude if LLD is merely associated or <g class="gr_ gr_419 gr-alert gr_gramm Grammar multiReplace" id="419" data-gr-id="419">a objective</g> causal factor in LBP, literature at hands is contradicting and <g class="gr_ gr_408 gr-alert gr_spell ContextualSpelling ins-del multiReplace" id="408" data-gr-id="408"><g class="gr_ gr_420 gr-alert gr_spell ContextualSpelling multiReplace" id="420" data-gr-id="420">non conclusive</g></g>.
Hip pain: A longer leg might be a predisposing factor in Osteoarthritis (OA). With length increasing, femoral head contact/ weight bearing area is decreasing. (+10mm- 5%/ +50mm - 25,1%). Combined with an increased tone in hip abductors caused by <g class="gr_ gr_434 gr-alert gr_gramm Grammar only-ins doubleReplace replaceWithoutSep" id="434" data-gr-id="434">elongated</g> distance between origin and insertion and an increased GRF puts the longer leg at risk.
Stress Fractures: Greater incidence of stress fractures in the tibia, metatarsals and femur of the longer leg appears consistent with the greater forces emitted trough the longer leg described under hip pain.
Other: There seems to be an association with trochanteric bursitis, patellar <g class="gr_ gr_409 gr-alert gr_spell ContextualSpelling ins-del multiReplace" id="409" data-gr-id="409">apicitis</g>, patellar joint incongruencies and <g class="gr_ gr_410 gr-alert gr_spell ContextualSpelling ins-del multiReplace" id="410" data-gr-id="410">myofacial</g> pain syndrome of the peroneus <g class="gr_ gr_411 gr-alert gr_spell ContextualSpelling ins-del multiReplace" id="411" data-gr-id="411">longus</g>

Outcome Measures

The most accurate method to identify leg (limb) length inequality (discrepancy) is through radiography. It’s also the best way to differentiate an anatomical from a functional limb length inequality.
- Radiography1,2:
A single exposure of the standing subject, imaging the entire lower extremity. Limitations are an inherent inaccuracy in patients with hip or knee flexion contracture and the technique is subject to a magnification error.
Computed Tomography (CT-scan)1: It has no greater accuracy compared to the standard radiography. The increased cost for CT-scan may not be <g class="gr_ gr_56 gr-alert gr_gramm Punctuation only-del replaceWithoutSep" id="56" data-gr-id="56">justified,</g> unless a contracture of the knee or hip has been identified or radiation exposure must be minimized.
However, radiography has to be performed by a specialist, takes more time and is costly. It should only be used when accuracy is critical. <g class="gr_ gr_50 gr-alert gr_gramm Punctuation only-ins replaceWithoutSep" id="50" data-gr-id="50">Therefore</g> two general clinical methods were developed for assessing LLI.
- Direct methods1,2: they involve measuring limb length with a tape measure between 2 defined points, in <g class="gr_ gr_52 gr-alert gr_gramm Grammar only-ins doubleReplace replaceWithoutSep" id="52" data-gr-id="52">stand</g>. Two common points are the anterior iliac spine and the medial malleolus or the anterior inferior iliac spine and lateral malleolus.
Be careful, however, because there is a great deal of criticism and debate surrounds the accuracy of tape measure methods. If you choose <g class="gr_ gr_47 gr-alert gr_gramm Grammar only-del replaceWithoutSep" id="47" data-gr-id="47">for </g>this method, keep following topics and possible errors in mind:
• Always use the mean of at least 2 or 3 measures
• If possible, compare measures between 2 or more clinicians
• Iliac asymmetries may mask or accentuate a limb length inequality
• Unilateral deviations in the long axis of the lower limb (eg. Genu varum,…) may mask or accentuate a limb length inequality
• Asymmetrical position of the umbilicus
• Joint contractures
- Indirect methods1,2: Palpation of bony landmarks, most commonly the iliac crests or anterior iliac spines, in <g class="gr_ gr_54 gr-alert gr_gramm Grammar only-ins doubleReplace replaceWithoutSep" id="54" data-gr-id="54">stand</g>. These methods consist in detecting if bony landmarks are at <g class="gr_ gr_53 gr-alert gr_gramm Grammar only-ins doubleReplace replaceWithoutSep" id="53" data-gr-id="53">(horizontal)</g> level or if limb length inequality is present.
Palpation and visual estimation of the iliac crest (or SIAS) in combination with the use of blocks or book pages of known thickness under the shorter limb to adjust the level of the iliac crests (or SIAS) appears to be the best (most accurate and precise) clinical method to assess limb inequality.
You should keep in mind that asymmetric pelvic rotations in planes other than the frontal plane may be associated with limb length inequality. A review of the literature suggest, therefore, that the greater trochanter major and as many pelvic landmarks should be palpated and compared (left trochanter with right trochanter) when the block correction method is used.

Exact procedure of the indirect measurement method: the use of <g class="gr_ gr_100 gr-alert gr_gramm Punctuation multiReplace" id="100" data-gr-id="100">blocks :</g>
<g class="gr_ gr_103 gr-alert gr_gramm Grammar multiReplace" id="103" data-gr-id="103">Patient</g> is standing with feet 10 cm apart, knees extended and equal weight on both feet.
The clinician places his/her hands on a bilateral anatomical structure: <g class="gr_ gr_93 gr-alert gr_spell ContextualSpelling ins-del multiReplace" id="93" data-gr-id="93">spina</g> <g class="gr_ gr_94 gr-alert gr_spell ContextualSpelling ins-del multiReplace" id="94" data-gr-id="94">iliaca</g> posterior superior, <g class="gr_ gr_95 gr-alert gr_spell ContextualSpelling ins-del multiReplace" id="95" data-gr-id="95">spina</g> <g class="gr_ gr_96 gr-alert gr_spell ContextualSpelling ins-del multiReplace" id="96" data-gr-id="96">iliaca</g> anterior superior or crista <g class="gr_ gr_97 gr-alert gr_spell ContextualSpelling ins-del multiReplace" id="97" data-gr-id="97">iliaca</g> left and right.
Now the clinician visually assesses if there is a length inequality, and if so, places a wooden board of 0,5 cm under the foot of the shorter side.
Keep placing thicker planks under the shorter side until <g class="gr_ gr_102 gr-alert gr_gramm Grammar only-ins doubleReplace replaceWithoutSep" id="102" data-gr-id="102">equal</g> length is reached, the thickness of the plank is equal to the leg length difference.
Although Reliability is highly dependent on the accurate measurements of the clinician, this method has shown excellent results in inter- examinator results <g class="gr_ gr_104 gr-alert gr_gramm Grammar multiReplace" id="104" data-gr-id="104">between</g> highly trained clinicians and medicine <g class="gr_ gr_113 gr-alert gr_gramm Punctuation multiReplace" id="113" data-gr-id="113">students .</g> Confounding variables reported <g class="gr_ gr_105 gr-alert gr_gramm Grammar multiReplace" id="105" data-gr-id="105">by</g> <g class="gr_ gr_111 gr-alert gr_gramm Grammar only-ins doubleReplace replaceWithoutSep" id="111" data-gr-id="111">literature</g> <g class="gr_ gr_112 gr-alert gr_gramm Punctuation only-del replaceWithoutSep" id="112" data-gr-id="112">are:</g> <g class="gr_ gr_92 gr-alert gr_spell ContextualSpelling ins-del multiReplace" id="92" data-gr-id="92">pelvical</g> asymmetry, incorrect positioning of feet, obesity, joint contractures, scoliosis and inaccurate measurement.
Leg length discrepancy after Total Hip Arthroplasty (THA)
Clinical signs: Patients can be categorized into three types according to the presentation of symptoms: 1) Most commonly, patients with pain from the resultant imbalance in muscle force around the hip and knee, as well as around the spine. 2) Pain and fatigue from the longer leg’s Quadriceps and hamstring muscles (flexed knee syndrome). Patients flex their knee during gait to maintain level pelvis. 3) Instability or dislocation as <g class="gr_ gr_115 gr-alert gr_gramm Grammar only-ins doubleReplace replaceWithoutSep" id="115" data-gr-id="115">result</g> of component orientation, the pain is often a result of hip and periarticular muscle fatigue from preventing subluxations.
Correctable cause after THA: initial postoperative apparent LLD. The initial postoperative LLD can be described as periarticular muscle spasm, lumbosacral scoliosis, and pelvic obliquity. They can each produce this early postoperative LLD. The physical result is a tilted pelvis relative to the floor, with the surgical <g class="gr_ gr_98 gr-alert gr_spell ContextualSpelling ins-del multiReplace" id="98" data-gr-id="98">hemipelvis</g> pushed inferiorly and the contralateral <g class="gr_ gr_99 gr-alert gr_spell ContextualSpelling ins-del multiReplace" id="99" data-gr-id="99">hemipelvis</g> pulled superiorly, giving an apparent LLD despite equal lengths from the anterior superior iliac spines to medial malleoli. The mainstay of treatment for this problem is patient education, reassurance, physical therapy muscle techniques, and possibly a temporary shoe lift. The patient should be reassured that most cases resolve within 6 months from surgery.

Differential Diagnosis

• <g class="gr_ gr_391 gr-alert gr_spell ContextualSpelling" id="391" data-gr-id="391">Pelvis</g> shift
• Low back pain (LBP) (=link)
• Idiopathic Scoliosis
• Iliotibial band syndrome (=link)
• Foot pronation
• Stress fractures lower extremity
  

Key Evidence

Gurney, B. “Leg length discrepancy”. Gait & posture 15, <g class="gr_ gr_17 gr-alert gr_spell ContextualSpelling ins-del multiReplace" id="17" data-gr-id="17">nr</g>. 2 (2002): 195–206
Brady, Rebecca J., John B. Dean, T. Marc Skinner, en Michael T. Gross. “Limb length inequality: Clinical implications for assessment and intervention”. The Journal of orthopaedic and sports physical therapy 33, <g class="gr_ gr_18 gr-alert gr_spell ContextualSpelling ins-del multiReplace" id="18" data-gr-id="18">nr</g>. 5 (z.d.): 221–234. <g class="gr_ gr_19 gr-alert gr_spell ContextualSpelling ins-del multiReplace" id="19" data-gr-id="19">Bezocht</g> <g class="gr_ gr_20 gr-alert gr_spell ContextualSpelling ins-del multiReplace" id="20" data-gr-id="20">december</g> 1, 2012

Resources

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Case Studies

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Recent Related Research (from Pubmed)

http://www.ncbi.nlm.nih.gov/pubmed/22744470
http://www.ncbi.nlm.nih.gov/pubmed/22744478
http://annals.org/article.aspx?articleid=745634
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1198238/
http://www.ncbi.nlm.nih.gov/pubmed/16026625

References

Review: Limb Length Inequality: Clinical Implications for Assessment and Intervention (2003) Rebecca J. Brady PT, John B. Dean PT;ATC, T. Marc Skinner, PT;ATC, Michael T. Gross, PT;PhD.Level of evidence: 1
Review: Leg Length Discrepancy (2001) – Burke Gurney
Level of evidence: 1
D.F.M. <g class="gr_ gr_393 gr-alert gr_spell ContextualSpelling ins-del multiReplace" id="393" data-gr-id="393">Pakvis</g> et al. <g class="gr_ gr_394 gr-alert gr_spell ContextualSpelling ins-del multiReplace" id="394" data-gr-id="394">Bepaling</g> van <g class="gr_ gr_391 gr-alert gr_spell ContextualSpelling" id="391" data-gr-id="391">beenlengteverschil</g> met de <g class="gr_ gr_395 gr-alert gr_spell ContextualSpelling ins-del multiReplace" id="395" data-gr-id="395">plankjesmethode</g>: <g class="gr_ gr_396 gr-alert gr_spell ContextualSpelling ins-del multiReplace" id="396" data-gr-id="396">nauwkeurige</g> <g class="gr_ gr_397 gr-alert gr_spell ContextualSpelling ins-del multiReplace" id="397" data-gr-id="397">uitkomstern</g>, <g class="gr_ gr_392 gr-alert gr_spell ContextualSpelling" id="392" data-gr-id="392">onafhankelijk</g> van <g class="gr_ gr_398 gr-alert gr_spell ContextualSpelling ins-del multiReplace" id="398" data-gr-id="398">ervaring</g> van de <g class="gr_ gr_399 gr-alert gr_spell ContextualSpelling ins-del multiReplace" id="399" data-gr-id="399">onderzoeker</g>. Ned <g class="gr_ gr_400 gr-alert gr_spell ContextualSpelling ins-del multiReplace" id="400" data-gr-id="400">tijdschr</g> Geneeskd 2003 8 <g class="gr_ gr_401 gr-alert gr_spell ContextualSpelling ins-del multiReplace" id="401" data-gr-id="401">maart</g>; 147 (10) E.B. LEVEL (2)
Lampe HIH, Swierstra BA, Diepstraten AFM. Measurement of limb-length inequality. Comparison of clinical methods with <g class="gr_ gr_390 gr-alert gr_spell ContextualSpelling ins-del multiReplace" id="390" data-gr-id="390">orthoradiography</g> in 190 children. Acta Orthop Scand 1996;67:242-4. E.B. LEVEL (2)
Gross MT, Burns CB, Chapman SW, Hudson CJ, Curtis CS, Lehmann JR, et al. Reliability and validity of rigid lift and pelvic leveling device method in assessing functional leg length inequality. J Orthop <g class="gr_ gr_410 gr-alert gr_gramm Grammar multiReplace" id="410" data-gr-id="410">Sport</g> Phys Ther 1998;27:285-94. E.B. LEVEL (2)
Changes in Pain and Disability Secondary to Shoe Lift Intervention in Subjects With Limb Length Inequality and Chronic Low Back Pain - A Preliminary Report – Yvonne M. Golightly et al (2007) – Journal of orthopedics and sports physical therapy E.B. LEVEL (2)
Conservative Correction of Leg-<g class="gr_ gr_388 gr-alert gr_spell ContextualSpelling ins-del multiReplace" id="388" data-gr-id="388">lengts</g> discrepancies of 10mm of less for the relief of chronic low back pain. – Ruth <g class="gr_ gr_389 gr-alert gr_spell ContextualSpelling ins-del multiReplace" id="389" data-gr-id="389">Defrin</g>, Sarit Ben Benyamin et al. (2005) Arch Phys Med Rehabil. E.B. LEVEL (2)
Erector Spinae and Quadratus Lomborum Muscle endurance tests and supine <g class="gr_ gr_387 gr-alert gr_spell ContextualSpelling" id="387" data-gr-id="387">leg-length</g> alignment asymmetry: and observational study – Gary A. <g class="gr_ gr_386 gr-alert gr_spell ContextualSpelling ins-del multiReplace" id="386" data-gr-id="386">Knuston</g> and Edward Owens (OCT 2005) Journal of Manipulative and Physiological Therapeutics. E.B. LEVEL (2)
The accuracy of the palpation meter (PALM) for measuring pelvic crest difference and leg length discrepancy. – Matthew R. Petrone, Jennifer Guin et al (JUN 2003) – Journal Orthop Sports Phys Ther VOL 33 (n°6) E.B. LEVEL (2)
 used to detect leg inequality and yet it is often cited and used by other authors.