Leg Length Discrepancy
What is a Leg length Discrepancy?
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 IngramSo 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
- 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
- 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.
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