Lower limb muscle strategies in low back pain patients.

When your client comes in with knee or foot/ankle issues do not dismiss the history of intermittent or exercise induced low back issues. It is possible that your client may be coming in with a loss of ankle rocker/dorsiflexion.  And, from your physical exam and screens, you may be at a loss as to why their ankle rocker is impaired. This problem further down the chain may simply be a compensation strategy to maintain function and postural integrity due to lumbar functional/fatigue challenges.

So you have sporadic low back pain and knee pain. Could they be linked ?

It has been a long believed rule that it is “all about the core”.  We have learned in recent years that this should be a very loosely accepted rule. 

In an old blog post (link) we stated some deeper truths:

Dr. McGill discusses the basic tenet that the hips and shoulders are used for power production and that the spine and core are used for creating stiffness and stability for the ultimate power transmission through the limb.  He makes it clear that if power is generated from the spine, it will suffer.  As gait experts, you should never forget this principle, if the spine and lumbopelvic interval is not strong/stiff and stable enough, the limbs can over power them and thus your gait, your running, your sport, could be causing you pain as the forces are poorly managed as they attempt to traverse the spine. 

Here we find a study referenced below that suggests that when the lumbopelvic interval is fatigued, that the lower limb muscles may step up activity.  This is a neat concept, not earth shaking by any means, but it nice to have studies that help solidify knowledge of compensation strategies.

“Individuals with low back pain (LBP) have been shown to demonstrate decreased quadriceps activation following lumbar paraspinal fatigue. The response of other lower extremity muscles is unknown. The purpose of this study was to determine changes in motoneuron pool excitability of the vastus medialis, fibularis longus, and soleus following lumbar paraspinal fatigue in individuals with and without a history of LBP.” 

What this study attempted to do was perform a controlled laboratory study designed to compare motoneuron pool excitability before and after a lumbar paraspinal fatiguing exercise. Twenty individuals (10 with history of low back pain) performed isometric lumbar paraspinal exercise until a 25% shift in paraspinal muscle surface electromyography median frequency occurred. 

What they discovered was that the soleus motoneuron pool excitability increased following lumbar paraspinal fatigue independent of group allocation and occurred in the absence of changes in vastus medialis or fibularis longus muscles. 

The authors propose that “increased soleus motoneuron pool excitability may be a postural response to preserve lower extremity function”.

When your client comes in with knee or foot/ankle issues do not dismiss the history of intermittent or exercise induced low back issues. They very well could be coming in with a loss of ankle rocker/dorsiflexion.  And, from your physical exam and screens, you may be at a loss as to why their ankle rocker is impaired.The problem further down the chain may simply be a compensation strategy to maintain function and postural integrity due to lumbar functional/fatigue challenges. 

Dr. Shawn Allen, one of the gait guys.

Reference:

J Electromyogr Kinesiol. 2011 Jun;21(3):466-70. doi: 10.1016/j.jelekin.2011.02.002. Epub 2011 Mar 8.Effects of paraspinal fatigue on lower extremity motoneuron excitability in individuals with a history of low back pain.Bunn EA1, Grindstaff TL, Hart JM, Hertel J, Ingersoll CD.

http://www.ncbi.nlm.nih.gov/pubmed/21388827

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