In the June 17th issue of Dynamic Chiropractic (page 26), I wrote the article "What if ... We Really Understood Why the Foot Was Pronated." I have received numerous calls about this article requesting more information about the various aspects of foot mechanics and concepts such as the windlass effect of Hicks. I would like very much to explain these things to each and every person that has called my office, however this is just not feasible. In talking to the numerous doctors and students, there was one question that I kept hearing with respect to the foot and it was painfully obvious that it needed to be the substance of another column.
To be very blunt about this I would like to state that diagnosis is really nothing other than applying one's knowledge of anatomy, the normal physiological function of the structures in question, and how the nervous system interacts with both; without the integration of all three, proper diagnosis and treatment is impossible.
The foot, when it dysfunctions, has a huge impact on the rest of the human frame, however the appearance of the foot in the static or open kinetic chain position is really an illusion. Let's look at some terms. Pronation is a good example. What is pronation? If you look in most textbooks on the foot you will find that few, if any authors actually take the time to discriminate between the differences in open kinetic chain pronation and closed kinetic chain pronation, when in fact they are unbelievably different. In the open kinetic chain position the calcaneus is everted, ABducted and dorsiflexed, and the talus remains stationary. In the closed kinetic chain position the calcaneus is once again everted (axial rotation about a sagittal axis), the talus is ADDucted and plantar flexed. You will note that the talus had no function in the open kinetic chain position and therefore the subtalar joint and the talocalcaneonavicular joints where not engaged, thus the action that is visible to the eye is opposite to the action seen during weightbearing and gait.
Obviously the same analogy can be said for the action of supination. In the open kinetic chain the calcaneus is inverted, ADDucted and plantar flexed with the talus remaining stationary. In the closed kinetic chain the calcaneus is inverted and the talus is ABducted and dorsiflexed, thus allowing for the windlass effect of Hicks, the longitudinal muscle-tendon-fascia-sling (made up of the peroneus longus and the tibialis anterior muscles). This allows the coupled actions of the tibialis anterior, the long head of the biceps femoris, and the converging axes of the transverse tarsal joint to function in a harmonious relationship during the gait cycle.
The significance of all this is that if you look at the foot in any other position other than dynamic closed kinetic chain function, you will be looking at an illusion; the illusion is that of dysfunction based upon appearance and a lack of understanding.
The consequences of foot dysfunction is manifested in the functional capacity of the rest of the leg and pelvis. To understand dysfunction it is first wise to understand the normal function. Too little time is spent on the teaching and understanding of -normals" as the term applies to the understanding of the biomechanics of the human body. Treating the end expression is what we are always taught. A good case in point is the misunderstanding of the cause of the so called T-L junction syndrome, but I will write about that in another column.
Consider the swing and single support phases of gait. During these phases, and on the stance leg and foot, the ilium rotates posteriorly with respect to the sacrum. The body begins a shift to the side of stance leg and prepares to create a functional oblique sacroiliac joint axis by the loading of the long head of the biceps femoris (secondary to the inferior dropping of the fibula). Subsequently there is load on the sacrotuberous ligament and the contraction of the piriformis and the gluteus maximus muscles; this initiates the form and force closure of the iliosacral joints and the resulting contraction of the ipsilateral multifidus. Increased nutation of the sacrum on this oblique axis will prepare the joint for heel strike at the moment of contact. The hamstrings, which are active just prior to heel strike, have their function dampened by the actions of the multifidus, sacrotuberous ligament, and sacral nutation activating the biceps femoris. The foot dorsi flexion is maintained by concentric contraction of the tibialis anterior muscle which will allow for foot plantar flexion by eccentric contraction just after heel strike. This of course will once again be followed by concentric contraction to effectively pull the tibia anterior in a line of progression over the talocrural joint.
After heel strike the action of the biceps femoris is diminished and the ipsilateral ilium rotates anteriorly with respect to the sacrum and the nutation action is decreased with the force closure compression of the sacroiliac joint slightly reduced. The action of the biceps femoris is slowly replaced by the action of the gluteus maximus which, by virtue of its 90o orientation to the sacroiliac joint, is much better suited to compress the sacroiliac joint. From reading current journals it is well documented that the gluteus maximus is coupled to the contralateral latissimus dorsi through the connection of the various muscles whose fascial continuities make up the lateral raphe.
At heel strike the trunk displays the classic position of counterrotation (right leg forward and left arm forward). This counterrotation, when considered in the light of energy conservation, storage and release, is critical in the understanding of functional and neurological rehabilitation of our patients. Clearly, a glance at the works of Gracovetsky, Bogduk and Vlemming, with a special interest in the posterior ligamentous or back force transmission system, indicates that the coupled motions of the latissimus dorsi, gluteus maximus, sacrotuberous ligament and hamstrings are all impacted upon by abnormalities in gait and, that gait itself can be altered as a result of coupled motion dysfunction.
We need to look at the insertion of the latissimus dorsi to appreciate its importance to our patients and their well-being. The latissimus dorsi, prior to inserting into the intertubercular groove between the pectoralis major and the subscapularis muscles, undergoes a coiling action (the inferior fibers become superior fibers and the superior fibers become inferior fibers at point of insertion). When we consider this with the same coiling that takes place with the sacrotuberous ligament we can easily understand the importance of the counterrotation action and the storage of huge amounts of elastic energy. In other words, the latissimus dorsi and the sacrotuberous ligament are none other than very intelligent dynamic springs that enable us to conserve and expend large amounts of energies at the precise moments of need.
The gluteus maximus, the vastus lateralis, the tensor fascia latae, and the iliotibial tract all function in a harmonious attempt to create stability and to disperse forces of tension created by the gluteus maximus contraction. It should be easy to see how the gluteus maximus and the tensor fascia effect the iliotibial tract. However to most, it is not at all obvious with respect to the vastus lateralis. The vastus lateralis functions during single support phase of gait as a counter action to the flexion moment of the knee joint, and as a result of this action the iliotibial tract is pushed lateral and its tension level is raised significantly.
Recent research has revealed that the distal aspect of the iliotibial tract actually inserts into the lateral joint capsule and has functional significance. The fibers of the iliotibial tract also insert into the tibia and are at 90 degrees to the patella tendon. Clinically this entire concept is important to the doctor of chiropractic when dealing with high performance and elite athletes, as well as the weekend warriors.
Conditions such as chondromalacia patellae and Osgoode Schlattters disease can be caused by dysfunction along this tension pathway. Normal biomechanical considerations like anterior translation of the femur on the tibia during mid-midstance to late-midstance phase of gait are checked and controlled by the tension developed in this system. This tension starts with the latissimus dorsi and is coupled with the thoracolumbar fascia, the contralateral gluteus maximus, the tensor fascia latae and the iliotibial tract. Looking once again at the rotary torsional aspects of the normal gait cycle, it should be of no surprise that we can conclude that the latissimus dorsi, gluteus maximus, and the entire expansion of the vastus lateralis also function as a spring mechanism to conserve and release energy when needed.
If we look very carefully we can now understand the common conditions like idiopathic rotator cuff tendinitis which, if we understand the normal biomechanics of the lower limb, can easily be a cause of contralateral rotator cuff tendinitis if there is dysfunction present along the aforementioned systems and pathways. Also conditions like hyperventilation syndrome could also be attributed to dysfunction along this system and, according to Dorman (p. 585-600 in the First Interdisciplinary World Congress on Low Back Pain and its Relation to the Sacroiliac Joints), -defects in this system may lead to higher oxygen demands." Taking this one step farther and looking at the concept of short leg/long leg, and without getting into the numerous causes of this, it appears that the discrepancy from whatever source during the gait cycle causes an increase in the patient's oxygen consumption and a higher metabolic demand at the heart level. Imagine, chiropractors actually affecting the oxygen consumption of the heart, it with scientific research and data. The problem of course is that you need to understand the function of the lower limb and foot, and the aforementioned coupled slings and coiled springs.
Based upon what I have written it would seem logical to look at our back pain patients from just another point of view: that is to treat and prevent back pain by coordinating trunk, arm and leg muscles, with the function of the foot and ankle so that the stored energies of torsional forces can be effectively utilized by the patient and not dispersed as forces of destruction.
According to Radin ("The Joint as an Organ; Physiology and Biomechanics," Abstracts, First Congress on Biomechanics, La Jolla, September 1990. Volume 2.1): Functional analysis, be it biological, mechanical or both, of a single tissue will fail to give a realistic functional analysis as, in all complex constructs, the interaction between the various components is a critical part of their behavior."
This material and much more is taught at the various MPI seminars. I have attempted to give an overview with some clinical correlates however, I would advise further study on these matters as they are very complex in nature and require time and clinical application. The science of chiropractic is evolving as we eat and sleep. There is now more research than ever before to show how important biomechanics are to the function of the human frame. There is great interdisciplinary communication with no ego involved. Science is science whether it be applied to chiropractic or to another discipline. Please make sure you are at the leading edge of current research.
Keith Innes, DC
Ontario, Canada
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