Leg Length Discrepancy

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What is a Leg length Discrepancy?


Structural:
A true bony difference in length of the lower extremities

Functional:
A difference in leg length attributable to asymemetry in joint position

What amount is significant?


Difference            Problem                                                Source

3 mm                     Running injury risk                                  Subotnick
5 mm                     Spinal compensation                               Friberg
6 mm                     Running injury risk                                  Brody
7 mm                     No problem < 7 mm                               Corrigan, Maitland
9 mm                     Lumbar facet angle changes                    Giles
10 mm                   Low back pain                                       Cyriax
15 mm                   Compensatory scoliosis                          Gibson
20 mm                   LE compensation                                   Vogel
22 mm                   Significant scoliosis                                 Papaloannu
40 mm                   Requires surgical correction                    Ingram

So as you can see there is plenty of debate of the amounts. Everyone is different so the truth is it depends!


How do I know if i have one?

The only true accurate way is Radiographic Analysis:

• Radiographic
• CT Scanogram
• MRI Scanogram

This is because the points you can measure from are movable and are likely to have moved due to the difference!

However it is unlikely that you will be having any of these done so we have to look at it by measuring the following:
  • Pelvic Landmarks
  • Iliac Crest
  • Anterior superior iliac spine (ASIS)
  • Posterior superior iliac spine (PSIS)
  • Knee Joint Line
  • Malleoli (ankle bony prominence) 
  • Plantar Foot (Heel) Contour

However:

Just because these measurements are showing a leg length discrepancy doesn't mean that you have one or don't have one. The body is very good at compensating. Here are a few potential compensations:

Increased Subtalar Pronation of Long Limb:
  • Very common
  • Typical with flexible (mobile) foot types
  • Can be a source of poor orthotic device tolerance
Increased Subtalar Supination of Short Limb
  • More common with rigid (hypomobile) foot types
Talocrural Joint: 

  • Increased Plantarflexion of Short Limb
  • Increased Dorsiflexion of long Limb with knee flexion in standing
Knee:
  • Valgus (knock kneed)on long side (More common in females)
  • Varus (Bow legged)on long side
  • Flexion (bent) contracture on long side
  • Hyperextension (beyond straight) on long side
Hip:

  • Chronic posturing with foot placement away from the midline of the body (abduction of hip) on long side.
Pelvis:
  • Upslip on long side (looks shorter though!)
  • Anterior Rotation on longer leg
  • Posterior Rotation on shorter leg
  • Obliquity: Frontal Plane Pelvic Tilt, can be a compensatory motion toward a Structurally Short Limb, resulting in a Lateral Scoliosis, concave toward “higher” side.

What can I do about it?

A Physiotherapist can assess you to establish if you have a discrepancy (true or apparent) and work out a treatment plan, which could involve orthotics (insoles), stretches, exercises and/or mobilisation techniques.





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