Department of Podiatry

Limb Length Discrepancy

Classification

structural / anatomical LLD
- difference in actual skeletal length of tibia or femur or both
- congenital / developmental / traumatic

functional LLD
- bony components are equal in length, but function assymetrically
- asymmetrical mechanics / soft tissue contracture
- environmental LLD
- uneven shoe wear or banking of roads / athletic tracks
- may accentuate, eliminate or reverse an existing LLD

Aetiology

structural / anatomical LLD
- congenital defects
- trauma (eg: motor vehicle accident)
- burns
- infection
- post-surgical shortening
- tumor
- hemiatrophy and hemihypertrophy

functional LLD
- pelvic / lumbar anomaly (eg: scoliosis)
- muscle contracture (eg: psoas)
- asymmetrical rearfoot pronation

Incidence

- figures range from 60-90% of the general population
- longer right leg more common
- high correlation with lower back pain

When is an LLD clinically significant ?

- no absolute value
- depends on ROM, activity, planal dominance
- a 3mm LLD may cause symptoms in a runner or someone who spends most of their day standing
- greater frontal plane motion of the rearfoot > more significant effect on limb length
- generally, treat if causing symptoms or greater than 1-2 cm.

- can occur in any joint in any plane
- depends on ROM available and size of LLD
- each patient is unique

subtalar joint
- pronation of 'long' leg
- supination of 'short' leg

ankle joint
- plantarflexion of 'short' leg

knee joint
- hyperextension / flexion of 'long' leg
- genu varum / valgum of 'long' leg

spinal
- a number of mechanisms
- compensatory sacral drop on the short side may result in:

1. no spinal compensation. Pelvic and shoulder tilt to short side
2. lumbar and cervical scoliosis with shoulder and/ or head tilt to long side
3. lumbar scoliosis with slight or no shoulder tilt to long side

- therefore, observation of shoulder tilt may indicate LLD but is not a good predictor of which leg is 'long' or 'short'
- also note that the scoliosis may be the cause of the LLD (diagnose by examining pt. non-WB)

Effects of LLD

(i) Back pain
- very commonly associated with LLD
- scoliotic compensation leads to compression of lumbar intervertebral discs: IVD herniation, OA
- asymmetrical spinal muscle activity: sciatica, nerve root compression

(ii) Hip pain
- due to compensatory pelvic tilt
- elevation of pelvis on longer limb causes a varus shift which decreases the articular contact area of the femur in the acetabulum: OA

(iii) any number of lower limb pathologies may be the result of a LLD due to compensatory joint mechanics

Diagnosis

- the key to diagnosis is ASYMMETRY in:
symptoms
shoe wear
history of unilateral inversion sprains
conscious adjustment to posture by patient providing symptomatic relief
asymmetries in gait analysis

Clinical measurement

structural
- pt. supine: ASIS to MM or LM, or..
- indirect test: pt. WB - place blocks under suspected shorter limb the measure blocks

functional
- pt. supine: umbilicus to MM
- pt. WB - measure from ASIS to the ground in NSCP and RCSP

radiographic measurement
- plain film radiography
- computed tomographic scanning
- magnetic resonance imaging
- problems: time, cost, radiation exposure, reliability, placement of subject in FP, magnification errors
- justifiable ?

Treatment

- heel lifts / full length lifts / shoe modifications
- if due to asymmetrical rearfoot motion, orthoses with different degrees of rearfoot control
- stretching of contracted muscle groups
- chiropractic adjustment of spinal alignment
- often requires a multi-disciplinary approach

Summary

- LLDs are very common
- 3 categories
structural
functional
environmental
- associated with
- lower back pain and hip pain
- Rx depends on size, symptoms, pt. activities
- multi-disciplinary approach is recommended

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References

Blake RL, Ferguson, H (1992) Limb length discrepancies. Journal of the American Podiatric Medical Association 1: 33-38.

Blustein SM, D'Amico JC (1985) Limb length discrepancy - identification, clinical significance and management. Journal of the American Podiatric Medical Association 75(4): 200-206.

Chambers MRC (1996) Leg length inequality: types, pathomechanics and incidence. Journal of British Podiatric Medicine 51(5): 74-80.

Click here for a link to a short article about limb length discrepancies.

For an amazingly detailed, beautifully illustrated summary of limb length discrepancy evaluation and management, follow this link to the MedNet limb length pages.

Content Approved by: Head of Podiatry
Page maintained by: Podiatry Webmaster
Last Updated: August 20th, 2002