Infinity Spine Center Blog

Walking on Unstable Ground

A very common postural finding among humans is one leg shorter than the other (leg length inequality).  In fact, one study that included 35 runners found that 34 (97%) had a short leg.  There are two reasons that you may have a short leg.  The types of short legs are commonly categorized as structural or functional (someone with a structural short leg could have a functional short leg as well).

 

A structural short leg occurs when there is an actual difference in length of one leg compared to the other.  An example of a structural short leg is when a bone in the leg (tibia) is shorter than the other.

 

A functional short leg on the other hand is due to a muscle imbalance or spinal misalignment, such as scoliosis.  Many times this is caused by a misalignment in the upper neck (cervical) region causing less than optimal input (dysafferentation) to a part of the brain (cerebellum).  This abnormal input to the brain leads to abnormal output to the muscles of the low back and hip region.  This leads to abnormal muscle tone (inhibition and facilitation).  We’ll go into more detail on this a little later.

LLI

Any architect will tell you that if the foundation of a building is unleveled chances are the building will not withstand the forces over time.  The human body is no different.  The consequences of these asymmetries result in less than optimal health of your spine which leads to decreased performance.  When most of us think about consequences due to a short leg, we typically think of biomechanical compensations, however, one study found that a short leg caused an increase in heart rate (see previous post).   As far as mechanical compromises in the body that commonly occur if the short leg and asymmetries are not addressed include:

 

  1. Stress fracture
  2. Back Pain
  3. Arthritis

 

In all three of these conditions the consequence is damaged tissue and decreased health and performance.

 

It’s important that you first find out if you have a short leg (according to the stats in the above mentioned study, chances (97%) are you have a short leg).  Second, we need to determine the cause of the short leg.  Two different scenarios exist:

 

1. Difference in leg bone length (diagram on left)

2. Abnormal muscle tone due to upper cervical misalignment (spinocerebellar tract) (diagram on right)

 

 

If you do have a true leg bone length difference, this causes asymmetrical forces into the hip joint, which causes tipping of the sacrum (see above left diagram).   Asymmetrical forces in the hip and tipping of the sacrum cause the spine to become unbalanced leading to misalignments in the spine.  Another compensation in the spine will be made in the neck (upper cervical) region known as the righting reflex.  The righting reflex is the body’s attempt to keep the eyes (also vestibular system) parallel to the horizon to maintain balance.  As a result of this righting reflex, muscles and ligaments in the upper neck have less than optimal length and tension due to the upper neck (cervical) misalignment.  This suboptimal length and tension in the muscles and ligaments can lead to a variety of symptoms such as headaches (see previous post for more details).

 

If your short leg is caused by abnormal muscle tone, it’s imperative that you have your upper cervical spine checked by a Chiropractor.  This is important because the location of the nerves (spinocerebellar tract) in the upper cervical spinal cord that supply input (unconscious proprioception) to the brain detailing position of the low back and hips.  When you have abnormal input to the brain, the brain registers this and it affects nerve output to the body  leading to abnormal contraction of the muscles (facilitation) or abnormal tone (inhibition) of muscles.

 

Whether you have a short leg due to a true bone length difference or abnormal muscle function in the hips, this causes the pelvis to tilt to one side.  When this tilting occurs the body compensates by developing curvature(s) in the spine, which leads to the head tilting (righting reflex) and ultimately an upper cervical misalignment.

 

What can you do about this?

1. Get checked by the Chiropractor to determine the cause of the short leg.

2.  Do corrective exercises that are specific to your posture.

    • These exercises provide stability to the spine.

3. Don’t wait till you have symptoms such as pain.

    •  If you have pain your tissues have already been damaged.

Resources:

British Journal of Sports Medicine (1991)

Gait and Posture (1996)

Chiropractic and Osteopathy (2005)

 

 


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