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

Fundamental Hip Biomechanics: Part 1

Hip Biomechanics

The following excerpted text is copywrited from the textbook; “Form and Function: The Scientific Basis of Movement and Movement Impairment” (Dr. S. Allen, Dr. E. Osar)


Frontal Plane Functional Biomechanics

The hip is a very complex joint.  It is a ball and socket joint with great stability and potentially great mobility.  One of the most critical and essential planes of motion and stability is the frontal plane of hip joint motion.  This plane (coronal/frontal) of motion and stability is largely determined by the hip abductor muscle (HAM) group through an axis of oriented in the anterior-posterior direction through the head of the femur.  The most obvious and simple function of the hip abductor muscles is to produce a movement or moment of abduction of the femur in the acetabulum in the frontal/coronal plane (as in a side lying leg lift).  As mentioned, this is a simple way to determine open kinetic chain range and open chain strength in this range but it is neither true nor transferable in theory or practicality when the foot is on the group.  When the foot engages the ground the typically usable functional range is much less and the muscular function is now to move the pelvis on the stable and somewhat static femoral head in the frontal plane.  Explained in another way, in this closed chain, the insertion of many muscles remains static and the force generated through the muscle will pull at the origin and generate movement at the joint in this manner.  In a nutshell, the hip abductor muscles (HAM) will produce either leg motion to the side (abduction) or it will produce a lateral bending or lateral flexing of the pelvis-torso into the same range of motion (abduction). 

The most critical and commonly considered hip abductor muscles (HAM) are the gluteus medius, gluteus minimus and tensor fascia lata-iliotibial band complex.  These muscles have the most favorable line of pull and all have a femur and pelvis attachment.  We will call these muscles collectively the HAM group.  In the stance phase of gait the body’s center of gravity (COG) is medial to the hip joint axis of motion.  Thus, in this single leg support phase of gait the tendency will be for the body mass above the hip to rotate or drop towards the swing leg side.  This gravitational movement should be offset by the concentric, isometric and eccentric muscular activation of the HAM group through the anterior-posterior oriented axis through the head of the femur.  Any functional strength deficits (concentric, isometric or eccentric) of the HAM group and/or neighboring synergistic stabilizers will result in an altered joint stability challenge because not only do the HAM and surrounding muscles product movement but they also generated joint compression and thus stability.  The possible undesirable outcome may be an altered movement patterning characterized by inappropriate muscle or muscle group activation in either timing, force, speed or coordination with typically coupled muscles.  These challenges to the joint and its normally expected movement patterns will result in the body’s search for more stable positions in the frontal, sagittal or oblique planes.  These newly established, yet less efficient, positions and patterns of movement are initially welcomed compensations but in time as the new accommodations become rooted in pattern the synergists and other recruitments become overburdened and further demand compensations from other neighboring muscles eventually resulting in pain, joint derangement and dysfunction.  These compensations in recruitment and movement eventually will lead to non-contractile soft tissue changes such as hip capsule pattern changes in tension and length. These non-contractile soft tissue changes can not only dictate or perpetuate the newly established aberrant joint movements but help engrain the abnormal movement patterns and their new neurologic patterns.