What does progressive weakness of the posterior compartment look like?

Look at this video carefully and what do you notice? Can you see the progressive dip in the left heel as time goes on while toe walking? This is a cardinal sign of lack of endurance in the posterior compartment, in this patient’s case tibialis posterior. Your differential, in addition to lack of type one muscle fibers, insufficient vascularity or mitochondria for whatever reason would be circulatory problems as well as conditions causing progressive motor weakness like myasthenia gravis.

Fatigue testing is very important because a lot of times the problem doesn’t come out till the person reaches say a half an hour, an hour or sometimes even many miles into the run or ride. Our job as clinicians is to try to diagnose the problem to the best of our abilities. Our job also is to “exploit their weaknesses” rather than “extol their virtues”. 

If you’re getting somebody with posterior calf pain or a foot drop, or maybe somebody who gets worse over time, consider fatigue testing.

Where your gait might break down.

Gait appears most robust to weakness of hip and knee extensors, which can tolerate weakness well and without a substantial increase in muscle stress. In contrast, gait is most sensitive to weakness of plantarflexors, hip abductors, and hip flexors. - van der Krogt

In the past few weeks I have shared my thoughts on some articles regarding low back paraspinal musculature fatigue and the subsequent effects on motorneuron pools, specifically excitability of the soleus and quadriceps. These shared thoughts are from recent papers in the literature (search the blog over the last week). These effects are suggested to indicate a postural response to preserve lower limb function. In other words, as paraspinal fatigue set in, lower extremity muscle compensation ramped up to sustain postural locomotion demands.  Obviously, one should think this a step further and translate it all into questions of assessment of ankle dorsiflexion (ankle rocker) and control of progressing knee and hip flexion when pertaining to these muscles. The issues of stability and mobility should heighten. The one big problem in these studies, and you have even likely had these thoughts during your clinical examinations, is that one cannot truly fatigue one muscle group alone especially during activity, nor can one assess a single muscle group during manual testing. Luckily we have EMG testing capabilities in this day and age and we can more easily look into the function and reaction of a muscle and its’ direct response reactions. 

Today I have an article by van der Krogt that we read long ago, but that which one of our readers brought back into our wheelhouse.  This is pretty amazing stuff.

“This study examines the extent to which lower limb muscles can be weakened before normal walking is affected. We developed muscle-driven simulations of normal walking and then progressively weakened all major muscle groups, one at the time and simultaneously, to evaluate how much weakness could be tolerated before execution of normal gait became impossible. We further examined the compensations that arose as a result of weakening muscles. Our simulations revealed that normal walking is remarkably robust to weakness of some muscles but sensitive to weakness of others. Gait appears most robust to weakness of hip and knee extensors, which can tolerate weakness well and without a substantial increase in muscle stress. In contrast, gait is most sensitive to weakness of plantarflexors, hip abductors, and hip flexors. Weakness of individual muscles results in increased activation of the weak muscle, and in compensatory activation of other muscles. These compensations are generally inefficient, and generate unbalanced joint moments that require compensatory activation in yet other muscles. As a result, total muscle activation increases with weakness as does the cost of walking.“-van der Krogt

So, if your client comes in with knee, hip or ankle pain and a history of low back pain, you might want to pull out these articles. You may want to consider which muscles are, according to this article, most robust and sensitive to weakness. Remember what I mentioned when i reviewed the soleus article ? I mentioned that the reduced ankle dorsiflexion range may be from a soleus muscle postural compensation reaction to low back pain. Today’s article seemed to confirm that this muscle group is sensitive to weakness. In today’s discussion, not only is the impairment of the hip ranges of motion or control of the knee (from quadriceps adaptive compensation) possibly related to low back pain, in this case, paraspinal fatigue but it may be a muscle group robust to weakness which is a darn good thing when the paraspinals go to nap.

Sometimes the problem is from the bottom up, sometimes it is from the top down. It is what makes this game so challenging and mind numbing at times. If this is all too much for you, in teasing out this quagmire of a system, just throw corrective exercises at your client and hope for the best. What is the worst that can happen if you get it wrong ? Stronger compensations on already present compensations … . . why not, it is good for return business (insert sarcasm emoticon).  But, lets be honest, if it was easy everyone would be doing it the right way. But the truth is that it is a long journey, and we are on the same bus of discovery with you all. 

Dr. Shawn Allen, one of the gait guys.

Reference:

Gait Posture. 2012 May;36(1):113-9. doi: 10.1016/j.gaitpost.2012.01.017. Epub 2012 Mar 3.How robust is human gait to muscle weakness?van der Krogt MM¹, Delp SL, Schwartz MH.

Do you know your stuff? Would you correct this child’s gait ? Give them orthotics, exercises, force correction, leave them alone ? 

Is he Internal Tibial torsioned ? Is he “pigeon toed” ,if that is the only lingo one knows, :(  Does he have femoral torsion ?  A pronation problem locally at the foot or an internal spin problem through the entire limb ? Or a combination of the above ? 

What’s your solution?

It MUST be based on the knowledge necessary to fix it, not the limits of YOUR knowledge. You can never know what to do for this lad from his gait evaluation, no matter how expensive your digital, multi-sensor, 3D multi-angle, heat sensor, joint angle measuring, beer can opening, gait analysis set up is. You can never know what to do for this lad if you do not know normal gait, normal neuro-developmental windows, normal biomechanics, know about torsions (femoral, tibial, talar etc), foot types etc.  It is a long list.  You cannot know what to do for this kid if you do not know how to accurately and logically examine them. 

Rule number 1. First do no harm.

If your knowledge base is not broad enough, then rule number one can be easily broken ! Hell, if you do not know all of the parameters to check off and evaluate, you might not even know you are breaking rule number one !  If everything looks like a weak muscle, every solution will be to “activate” and strengthen and not look to find the source of that weakness.  Muscles do not “shut down” or become inhibited because it is 10 minutes before practice or because it is the 3rd Monday of the month. You are doing your client a huge disservice if you think  you are smarter than their brain and activate muscles that their brain has inhibited for a reason. What if it were to prevent joint loading because of a deeper problem ?  If every foot looks flat and hyper pronated, and all you know is orthotics or surgery or shoe fit, guess what that client is prescribed ? If all you see is torsions, that is all you will look to treat. If all you see is sloppy “running form” and all you know is “proper running form” forcing your client into that “round peg-square hole” can also lead to injury and stacking of compensation patterns.  

One’s lack of awareness and knowledge, are one’s greatest enemies. If you don’t know something exists, because you’ve never studied or learned it, how can you be aware of it ? If you’re not spending enough time examining a client, you might not be aware of an issue even though you may be knowledgeable about the issue.
One must have both awareness and knowledge. One must also be aware that compensations are the way of the body. What you see is not your client’s problem. It is their strategy to cope.

Are you helping your client ? Hurting them ?  Adding risk to their activity ? Are you stepping beyond your skill set ?  

Rule Number 1: First do no harm. 

Shawn and Ivo

PS: we will get to this case another time, we just wanted to make a point today about the bigger problems out in the world.

the gait guys