Detailed Explanation of Professor Irvin Korr’s Theory of Facilitated Spinal Segment

This theory is attractive and partly explains the results obtained by osteopaths. It is the result of long years of scientific studies by Professor Irvin Korr and his team. It sheds light on the action of manual therapy.

“When all parts of the human body are in order, we have health. When they are not, we have sickness. Adjusting what is wrong removes the disease “

(Still 1910)

Structural treatment in osteopathy

Any functional anomaly corresponds to a structural dysfunction. We are therefore looking for what structures are disturbed. Depending on the level of intervention, there is a corresponding “structural” osteopathy, which mainly affects the locomotor system.

Today’s structural osteopathy is a continuation of the original osteopathy practised by Dr. Still (the founder of osteopathy).

Structural osteopathy focuses on manually treating certain chronic or subnormal acute states of the neuro-musculoskeletal system. By subnormal states we mean the states situated between the limits of the normal and the limits of the pathological.

As we have seen:

The neuro-musculoskeletal system is “the primary machinery of life”. All other systems are at its service.

Dr. Irvin Korr


The needs of the neuro-musculoskeletal system vary according to the moment. For example, one moment we sit and then abruptly we get up and we run to catch a bus. Our metabolism accelerates, the heart, lungs, muscles and glands increase their activity. All these changes are controlled at every moment by the neurovegetative system whose centres are located in the spinal cord, the brainstem and the brain.

At different segments of the marrow, the fibres of this system exit through the conjugation holes of the spine before being distributed to the various organs. On their way, they rub shoulders with the different structures of the intervertebral joint (meninges, disc, capsules, ligaments, articular processes, costo-vertebral joints).

According to Professor Irvin Korr, a lesion of one of these structures in relation to nerve fibres may cause a local or remote reflex reaction causing not only discomfort or pain, but also changes in the activity of the patient, the neurovegetative system and thereby changes in the organs these nerve fibres innervate. This phenomenon affects not only the fibres of the neurovegetative nervous system, but also all the other nerve fibres (sensory and motor) of the medullary segment involved. Through the pair of spinal nerves that emerge, it is ultimately a whole metamere that will be concerned (dermatome, viscerotome, sclerotome, myotome).

Here is what is written about it; Professor Irvin Korr in his theory on segmental facilitation (The facilitated spinal segment):

  1. “Normally, efferent neurons do not discharge in response to each influx that stimulates them. An efferent neuron only discharges if its membrane potential has been brought to a sub-threshold value by the other afferent fibres that articulate with it. In other words, it must be facilitated before unloading. This represents a kind of “insulator” for our nervous system.

  1. “In the lesioned segment of the medulla, this ”insulator“ no longer functions, and a large number of efferent neurons are maintained near their discharge – or even being facilitated – even at rest by chronic afferent bombardment from metamerically related structures with neurons: dermatome, viscerotome, sclerotome, myotome.

  2. “Proprioceptors are, without a doubt, an important source of this type of afference, but any metameric structure may be the origin of a pathological organ, a trigger point – or any other inflamed or irritated structure may be a chronic source of afference to the marrow and may be responsible for more or less toned facilitation (a “trigger point” is a major point of myoaponeurotic what is this? tension.) The palpation of it is very diagnostically useful and therapeutic) “ 

  3. “Any influx or contingent of additional impulses can cause these efferent neurons to be discharged. The origin of these impulses is the cerebral cortex, the centres of equilibrium and posture, the bulbar centres, the cutaneous receptors amongst others. If this afferent bombardment is sufficiently large and persistent, the facilitated neurons and the organs they innervate may be continually maintained in a state of excessive activity.

  1. “The state of facilitation can extend to all the neurons that have their cell bodies in the medullary segment that innervates the lesioned joint, which includes the cells of the anterior horn, the pre-ganglionic fibres of the system, sympathetic nervous and apparently the spinothalamic fibres. “

  1. “Since a structural disorder (an osteopathic lesion) sensitizes a segment of the medulla to the impulses coming from all the sources mentioned above, the segment of the medulla lesion should not be considered as a centre of centrifugal irritation, but rather as a lens towards which the irritations converge. As the barriers of the “insulator” are weakened in the segment in lesion, any excitation is channelled towards the motor nerve pathways which leave this segment. A current of air, a slight shock, will result in a response, usually at the level of the facilitated segments, and therefore pain, cramp or a cutaneous reaction in the tissues innervated by these segments. “

  1. “This is a truism in neurophysiology: When one function is excited, another, it’s opposite is simultaneously inhibited. While during our studies we have not looked into this aspect, there is no doubt that in the medullary lesion segment, the facilitation also extends to neurons that exert inhibitory influences on other neurons or other organs. “

“We can therefore conclude that an osteopathic lesion corresponds to an facilitated medullary segment, maintained in this state by influxes of endogenous origin which reach the marrow by the corresponding dorsal root, the structures which are under the control of the fibres. Efferents of this segment are potentially exposed to excessive excitation or inhibition. “

(Korr, 1947, 1976, 1978).

And Professor Irvin Korr adds:

“If the importance of the proprioceptors in the mechanism of the osteopathic lesion is admitted, we must not neglect the fact that any metamerically related structure with the medullary segment affected may, in the same way, create or maintain a state of lesion. In fact, any source of afference, whether in metameric relationship or not, can exert influence through the network of association neurons.. “

” To all these sources of influx must be added the supra-segmental sources, all the superior centres, from the medulla oblongata to the cerebral cortex, which act through the descending medullary pathways, sources of continuous influx and of very variable volume. They exert their influence (excitatory or inhibitory) on efferent neurons at all levels of the spinal cord. “

“It is therefore very important to remember that the efferent neurons represent final common pathways, these pathways being themselves the culmination of a host of influxes of all kinds that add to the influx of ???? Therefore, it can not be inferred that joint disorders – or osteopathic lesions – can not be considered as an ultimate cause of disease – rather they represent one of the many aetiological factors that operate simultaneously in the body, establishing a pathological process.

In fact, one wonders whether there has ever been a single cause for any effect, and whether there has ever been an isolated aetiological factor for any clinical entity. Each factor acts in the context of many other factors and causes certain effects only in a combination of certain factors. The osteopathic lesion is one of the most important factors – it is a sensitizing, predisposing, localising and channelling factor. The osteopathic lesion sensitizes a segment of the cord, weakens its protective barriers and facilitates.

It does not necessarily cause symptoms, and even when it is symptomatically silent, it can be discovered. This is not to minimize the importance of the osteopathic lesion, on the contrary, it is to widen the concept. Importantly, it proves that osteopathic diagnosis and therapy can make a contribution to preventive medicine. “

Thus, for example, the increase of the activity of a nerve receptor due to its irritation in one of the elements of the articular segment is transmitted to the corresponding medullary segment. If the initial irritation persists, this segment of the medulla will be solicited permanently. The corresponding efferent neurons will be bombarded even at rest by afferent influxes. As their threshold of response decreases, these neurons will be facilitated. The slightest additional information will cause these effector neurons to unload, keeping the different areas of the metamer corresponding to them in excessive activity.

The information thus flows from the receptor to the medullary segment, from the medullary segment to the metamer and hence to the initial receptor. It is created by a system of feedback, a real “overstimulation loop.” Thus, the segmental pain or functional discomfort felt by the patient, the indurated (hardened) muscle cords or the reductions in mobility of a vertebral segment relative to the above and underlying segments palpated by the osteopath, would be the result of this segmental facilitation now keeps these structures in a sub-normal state of excitement.


Can it enlighten us on the action of manual therapy?

Here again is what Professor Irvin Korr tells us about this:

“Here we can only try to guess, but at least our estimates are based on solid and experimentally proven assumptions”

“The manipulative methods that osteopaths apply, are usually addressed to muscles remained in a permanent state of contraction, unable to relax spontaneously even if the excitement is removed (state of contracture).”

“Relaxation of these muscles leads to a passive increase in the length of their fibres, which implies a decrease in the tension exerted on the proprioceptors of the muscles and tendons, the diminution of this tension reduces the number of influxes sent to the marrow by receptors and thus the level of facilitation of the medullary segment in question. Since excessive tension of the muscles and tendons, due for example to some bone movement, tends reflexively to produce more tension, manipulations by decreasing the overall tension break a vicious circle. “

“Another vicious circle can occur that can be broken by manipulative therapy: we said that the facilitation of a segment of the medulla includes the facilitation of sympathetic pathways. This facilitation of sympathetic pathways can lead to a state of sympathicotonia susceptible of causing a visceral pathology.

The latter, once formed, will behave as an additional source of bombardment for the facilitated segment, aggravating the somatic lesion which, in turn, will cause more intense irritation of the viscera. Relaxation of the muscles by manipulation can break this vicious circle by decreasing the discharge frequency of the proprioceptors. Even if this irritation can only be suppressed for a short time, the action of natural healing processes is still favoured. “

“Thanks to a manipulative rebalancing of the skeleton and thanks to a readjustment of the posture, the original cause of the stress, that is to say the excessive tension of the muscles, tendons and ligaments, can be eliminated, making the results obtained more durable. . “

“This is undoubtedly a very schematic version of the fundamental consequences of manipulation, but it can serve as a basic assumption and guide for further experimental research.”

In other words, when an osteopath restores the mobility of an articular segment of the spine (mobility being a very relative notion), it would have a double action locally and remotely. Such manual treatment, given at the right time and with good will, could prevent future deteriorations and greater evils since it would break the vicious circle of this facilitating loop that keeps local and remote structures in a sub-normal state of being. excitation.

In conclusion, this neurophysiological theory of segmental facilitation is now accepted by all schools of structural osteopathy, including the British School of Osteopathy. It also makes it possible to give a scientific explanation to the notion of “sub-normal” states resulting from this permanent overstimulation that may in the long run either degenerate into a pathological state, or be normalized by the hands of the osteopath.

How can blockages be related to pathological conditions?

How can joint disruption (bone and soft tissues):

  • Have local and remote repercussions,

  • Be related with pathological conditions, such as asthma or cutaneous pathologies (eczema, psoriasis)

  • Be detected and favourably corrected by osteopathic manipulation and thereby correct all the disturbances (symptoms) associated?

Each osteopath has a very personal perception of his relationship to the patient and therefore a different definition of Osteopathy. Whatever these differences are, life is complex and the difference rewarding:

“The hyper-specialization of science joins the inability to think what is global, connected, and complex. Science ignores the complexity of reality”.

Edgar Morin, research director at the CNRS

Osteopathy focuses on mobility restrictions and their correction. This approach, codified by Still, is not so recent:

“It is necessary to possess a solid knowledge of the spine, because many affections are indeed caused by a defective state of this organ”

HIPPOCRATE De Articulis §45.

Mobility restrictions, or osteopathic dysfunctions, are the consequence of a neurological disorder prepared well in advance. The nervous system, a great messenger, bringing together all the tissues of an organism, is obviously the key element to try to understand how all the symptoms associated with an osteopathic lesion can interact and especially how osteopathic manipulation can work?

How can joint disruption (bone and soft tissues) have local and distant repercussions, be in relation with other pathological factors, be detected and favourably corrected by osteopathic manipulation and, consequently, all associated disturbances?

For a physiologist, it seems reasonable to think that the resistance to movement, which characterizes the articular osteopathic lesion, is the product of the action of one or more of the muscles that mobilize the incriminated joint. The muscles are the only active tissues, producers but also shock absorbers of the movement, this antagonistic role allowing to make the movement harmonious! These two functions of creation and energy absorption are based on the same cellular mechanism, that of contraction. The osteopathic diagnosis is based on the search for ease or restriction of mobility: it is in its braking functions that the muscle can become the major and highly variable obstacle to mobility in the joints.

In structural techniques, velocity and amplitude are important criteria.

In functional techniques, emphasis is placed on ease of movement, and resistance to motion in the metamere lesion appears to vary exponentially, with resistance in a normal metamere varying linearly.

The restriction found in lesioned joints is the active opposition or physiological protest of the muscle against a particular directional movement, and “ease” or facilitation ??? represents co-operation and muscular submission in the opposite direction. This muscular resistance is not due to a phenomenon of inextensibility or viscoelastic disturbance as for the ligaments, but to changes in the degree of activation or deactivation of the contractile mechanism, that is to say in the degree of contraction of the muscle .

Functional techniques go in the direction of easy movement, bringing closer muscle insertions, reducing tension and muscle length. The disparity between the intra- and extra-fused ????? fibres decreases; the movement is slow as opposed to the triggering accident, the central nervous system has time to adjust the level of gamma activity by decreasing the discharge frequency and the muscle can return to its neutral position. The compression of the joints is relieved by the same methods

Treatment must take into account all the disturbances of the body diagram, the associated emotional and visceral disorders, the sensitivity of each person, the use he makes of it, the neuro-motor reprogramming or proprioceptive education if necessary, the correction. defective nutrition, dental rebalancing, soles …

Returning to the CNS: In fact, the spinal cord does not read the signals individually, but rather seems to be dealing with signal complexes presented to it collectively from thousands of information stations. The marrow seems facilitated when the information is contradictory, the signals are unintelligible (sort of seasickness): the high-sensitivity spindles falsely inform that the muscle is stretched almost to the maximum, whereas it is actually shortened. The medullary segment is dismayed and becomes disturbing for any physiological activity in which it participates. A manipulation consists in restoring an adequate sensory function allowing the segment to work harmoniously. The sympathetic hyperactivity induces an increase in the afferent discharge of the spindle, facilitating self-maintenance of the vicious cycle of osteopathic dysfunction.

Life is not composed of visceral functions, we do not peristalte, we do not vasodilate … all activity sets in motion all or part of the body, and the substratum, essential for all these activities, is the contraction of the skeletal muscles . Life is expressed through the contractile processes of striated muscle, myriad of carefully controlled movements. Implicit conclusion in the globalist osteopathic perspective, the musculoskeletal system is the primary machinery of life. This primary biological machinery is directed by the central nervous system, which acts in response to continuous sensory information: the function of heterokinesis . The viscera are concerned with the care and maintenance of this neuro-musculoskeletal system, providing food, elimination, defence, repair: function of homeostasis. The mediator indispensable for permanent adjustments of visceral to somatic is the sympathetic nervous system, under the CNS (hypothalamus especially), sensory information and chemical modifications of the blood.

Health requires that there is a continuous harmony between the visceral functions and the demands of the soma and the environment. Health requires a smooth functioning of our somatic machinery (neuro-musculo-skeletal), which is the source of most of the sensory information that reaches the spinal cord.

As a result, poor health and illness can be attributed to a communication breakdown between the two main body components, the soma and the visceral. Disorders resulting from this rupture can occur in several ways: – when the demand of the musculoskeletal system is excessive or inappropriate. – when the CNS receives such faulty information that it can not respond in an appropriate way – when the viscera provides inappropriate, inadequate or confusing responses to somatic demands.

The tensions, the imbalances, that reign in an injured tissue, be it a bone, a joint, a ligament or a muscle, are continually reported to the marrow thus blurring the transmission of normal sensory patterns.

This interference associated with that due to nerve irritation brings out, notice one or more individual segments as well as tissues or organs of the same metamere.

Thus, the function organized vertically in the marrow becomes manifestly horizontal at the level affected (the facilitated level) and the clinical disorder must then be seen under a segmental angle.

Offensive or offensive tissues present detectable changes on the surface of the body: muscular tension, tissue texture, visceral and circulatory function, secretory function … all these elements being an integral part of the osteopathic diagnosis.

The osteopath seeks local signs, mobility restrictions, muscular tensions, tissue and vascular changes, associated visceral disorders and uses the musculoskeletal system to break a vicious circle whose essential element is medullary. Medullary facilitation makes it possible to understand, by the necessary summation of multiple stimuli, that a “blockage” does not happen by chance: the region has been preparing for a long time to react in a brutal and excessive way to a rather trivial triggering factor. (The small walk, the small slip …) any phenomenon is interdependent of what precedes it.