The causes of Osteopathic lesions are the thousand forms of violence and strain to which the human body is subjected—to which indeed man subjects it.  Compared with animals these are as a thousand to one.  The business of the animal is to protect itself from such things, and except in the comparatively rare occasions of its fights it does so.  The business of the human being on the other hand is to harness and control the forces of nature, and the stress of this control rests finally upon the mechanisms of his body.  Nor is her body exempt, for the stressful contact of human life with the forces it controls has led to the great development of the human brain, with a consequent and necessary enlargement of the female pelvis, to admit of its being born; which enlargement is out of proportion, mechanically, is a mechanical weakness with increased danger of lesion, and at a point that is the mechanical axis of the body and more subject to strains than any other part.  Probably more than half of the women who have been examined by osteopathic physicians in the last half century have had lesion of the sacro-iliac articulation.

    Comparing the mechanisms of the animal body with those of the human body, we find further reason for the large number of lesions found in the human body.  In the prone position of the framework the force of gravity acts at one angle; in the erect position at ninety degrees from this angle.  The joints, the stresses, the weights and pressures in the animal body were adapted for the horizontal position, in which they have the greatest amount of protection that is possible along with the necessary motion.  In the erect position the angle is changed enough to destroy completely many of these protective devices.  For instance the articular planes of the spine and those of the transverse processes for the ribs are flat to the direction of gravitation in the horizontal position, while in the erect position they are parallel to it, and much more exposed as a consequence.  The sacro-iliac articulation also is not adapted for bearing the weight of the body and all of its muscular efforts as well, but a large-9-in fact, the larger—part of this in animals is borne by the forelegs; yet in the human subject this is first subjected to extreme torsion from the erect position, it’s thrown off its balance by the tilting of the pelvis, and then is forced to bear the strain of the erect position and of all the effort put forth by arms and trunk as well.

    And the human spine is derived from the animal spine.  Undoubtedly compensation is made for this change to the erect position—the adjustment of structure to function is an automatic thing in higher animals—but also that adjustment is never complete.  The ages of heredity are magnificent as compared with the race history of the human family.  Each individual passes again through an epitome of the evolution of its race, re-enacting its race history, structurally as well s otherwise.  And though each individual is also re-created by its parents, under the influence of their environment and efforts, yet the balance struck between the forward reaching heredity and the backward reaching re-creation is much nearer the present than the past.  The mechanical devices of the human body are still weak with reference to the erect position, the position in which it mostly receives its strains and shocks.  For a further illustration, again comparing the animal with the human spine, we find in the latter the joints of the lumbar region extended to the limit until they are in effect telescoped, while those of the dorsal area are correspondingly flexed—constantly in a state of semi-flexion, as compared with the horizontal animal spine bearing its weight transversely.  In these positions it is put through an immensely wider range of motion and under immensely increased mechanical strain.

    This is the background against which must be drawn the picture of the causation of mechanical lesions in the body.

    There is always a force greater than the power of any structure to resist.  Even in animals osteopathic lesions are found in plenty, as shown in the reports of the A. T. Still Research Institute.  In human beings they are merely more in proportion, as his mechanism is somewhat perverted, and his use of it violent.

    We think of these forces of disorder as being of a violent character.  And indeed the most serious lesions are caused by external violence.  But there is also much internal violence, and there is also the prolonged warping force, whose effect is slow but none the less serious; whose total is, as a matter or face, probably greater than that of the other two combined.  To these must be added forces that weaken the mechanism itself.

    We may classify the sources of lesions therefore as:

    External violence.

    Internal strain (muscular).

    Gradual warp.

    Pathological weakness.

    In reference to external violence, it proves to be not easy to get a clear record of the cause of a given disorder.  These do not occur in the presence of the physician; often they occurred years before.  All that he can note is the effect.  Classifying of these accidents and shocks with a view to prevention is not possible yet.  We find a rather curious thing, namely, that people do not often remember even the serious accidents that are responsible for the more serious of these disorders.  The reason for this is doubtless that they have not been taught to associate disease with disorders, i.e., with such accidents.  That which is a daily observation with the osteopathic physician is as yet a novel and a strange doctrine to the people in general.

    The greatest number of violence lesions comes probably from falls; next ranks accidents of various kinds, and then blows, as blows on the neck.  A rather frequent cause of lesions is the playful habit of pulling a chair from under someone about to sit down.  In the resulting shock the sciatic ligament is tensed by the position so that the elastic yielding of the sacrum is less, the spine is strained forward compressing the discs so that the full unrelieved shock from the descending weight of the trunk comes against the sacro-iliac joint.  This is especially liable to produce serious lesion if one side strikes first, as the descent of the opposite side then brings strong leverage action to bear on the articulation.  The suddenness of the shock will the more easily cause a lesion, just as the quick pressure is more effective in correction, because there is less time for the distribution of the pressure through the elastic medium of the tissues; which in the one case acts to cause, in the other to correct, the lesion—according to the direction of the force.

    It is the sudden, violent shocks that cause the radical lesions.  Let us make an examination of the mechanics of the joint in relation to such violence.

    In the first place we have solid structures, bones, bound together by flexible material; and these solid structures move on each other.  They move on each other, and they remain in contact while doing so.  In such a case one of two things must necessarily be true of that flexible material which holds them together—either it must be elastic, or it must be fastened at the center of motion of the bone that moves, and move radially as it moves.  Otherwise no motion would be possible without tearing the material.  Both of these things are true, as it happens.  There is one kind of ligament that is strong and very slightly elastic, which acts radially; and another kind that is quite elastic, not radial in its motion.  Also it is evident that this binding material does not keep the two bones from passing beyond their normal limits of motion—it merely holds them at a constant distance while they do so.  It is not their function to limit them otherwise.  That they do so limit them is due to the fact that beyond the point of normal motion the surface of the bone is no longer smooth or no longer permits of radial motion.  Beyond the limit of normal motion therefore the angle of the surfaces to each other is changed, and the function of the joint as such is destroyed.  It is under those circumstances that it remains in false position as a lesion.  It may be very lightly held at first, but the factors that hold it as a lesion are likely to increase as time goes on and it is uncorrected; for it seems to be the fact that recent lesions are far easier to correct and remain corrected more easily than those of some standing.

    It is the muscles, which act for the most part parallel to the plane of the joint surfaces, that should constitute the protection of the joint against lesion.  Muscle is really a powerful thing.  Consider the leverage of the elbow through which the biceps acts—attached about an inch from the center of the joint, or fulcrum, the lever is from fifteen to eighteen inches long; to lift ten pounds in the hand requires about one hundred and fifty pounds of force when the forearm is horizontal.  So of the other bones in the body in proportion to leverage.  Their power is adequate to protect joints normally.

    It is when they are overpowered by the other leverages of the body itself or are taken off their guard that lesion is mostly produced, or when coordination of the body’s movements is faulty or slow.

    It can be seen from this how necessary it is to have the patient relax when correction is attempted.  With relaxation complete, the correction of lesion is often unbelievably easy with proper technic, except in long standing or in extreme lesions.

    The theory of the immunity of drunken men from hurts in falling is probably incorrect, when it states that this is due to his muscles being all relaxed.  It is difficult to relax voluntarily—it is the business of muscles to contract to protect joints.  What does happen is that the muscular reaction is slow, so that the shock of the fall is widely distributed—as it would not be if the muscles were completely relaxed, nor of course if they were violently contracted under the influence of fright.  The falling of a dead body differs by immense degrees from that of a drunken man.  In stage falls also there is probably never complete relaxation—it would probably be found impossible to drill the nervous system so thoroughly as to make it possible; but it is possible by training to over come the element of fright which brings on over-contraction with increased danger, and to secure enough relaxation to allow the distribution of the shock.

    In the matter of the prevention of lesions in falls and accidents therefore the proper thing would seem to be first never to allow a joint to be moved to its extreme limit, and to keep the position and motions of the body always securely under the control of its muscles.

    Direct blows on joints are responsible for lesions of ribs quite frequently, of the cervical vertebrae at times, and of the sacrum rarely.  Any severe shock will, however, be distributed through the body, decreasing as it spreads, until it finds articulations whose planes are parallel to its force; then if sufficient force is left, lesion may be produced.

    By internal violence is meant contracture of muscle under some pathological force.  As said, this contractile forace may be very great and may last for long periods.  With such a contracture existing in some muscle, then even normal movement of the part may cause it to overpower the muscles opposing it on the opposite side of a joint, and to produce lesion.  A familiar instance is the ordinary “crick in the neck,” in which certain cervical muscles are contractured under the shock of cold, by nerve shock reflected from the thermic centers in the cervical cord; at the lower end of this contractured muscle lesion of the rib to which it is attached will commonly be found.

    The subject of warp lesions is a very vast one.  Probably every occupation that is at all monotonous or mechanical has its typical warp.  Very great benefit would come to the public from a statistical study of this matter with a view to prevention.  Many of these have been commented on.  Most important of these are the sitting position, and the position in sleeping.  High heels exact a toll in human life and health whose total would be astounding could it be reckoned.  The high heel takes tension off of the rear thigh muscles, and so allows the pelvis to assume a steeper angle; throwing the sacro-iliac ligament off of its plumb, leading to lesion of this joint; stretching the anterior spinal tissues and telescoping the articulations in the rear.  It is not uncommon to find the spine bent into a series of antero-posterior curves, with lesions at various points.  These may be corrected but will appear at other points in a short time if the deformity of the shoes is not corrected.

    The mechanics of the warp lesion are practically the same as those of the major force lesion.  Instead of the sudden violence overcoming the protective action of muscle and ligament there is the gradual stretching of them.  The mechanical positions and relations that are assume are the same except that there is less tension in the stretched ligaments; less indentation; greater ease in correction at first; but there is probably much less tendency to spontaneous correction.

    When, however, a lesion resulting from warp has stood for some time it is probably quite indistinguishable from a major-force lesion.

    The border-line between a normal state with muscles relaxed at the limit of motion of any joint, and a warp with stretched tissues, is very faint.  So also is the border-line between a warp and a warp lesion in which normal position is not assumed for mechanical reasons.  The latter distinction is not important in technic.

    Weakening of the ligaments of the whole body occurs in conditions of thyroid insufficiency.  Weakening of ligaments of individual joints is likely to occur in connection with vaso-motor disturbance reflected from some internal abuse; in which case it occurs around the specific center for that organ and is due to the inflammation congestion and swelling of the ligaments.

    There are certain points of natural mechanical weakness in the body.  Every mechanism has its structurally weakest point.  Mechanically weak points exist wherever a small part joins a large part.  Such points are found in the human body at the juncture of the spine with the pelvis, with the reinforced chest box, at both upper and lower ends, and with the cranium.

    Mechanically weak points occur where the angle of motion changes abruptly.  These are found at the sacro-lumbar joint, at the eleventh dorsal, the seventh cervical (heavily reinforced) at the axis and atlas.

    Mechanically exposed points exist at the ends of the attachments of large muscles or of any muscles subject to strain, as those of the shoulder, the scalene, the pectoralis minor.

    Danger points exist where articulations are small and motion slight, when strain, even well distributed strain, includes them; as the upper dorsals, the last ribs.

    Physiologically exposed points exist at the centers for organs frequently strained or abused, as the organs of internal secretion; these are the third cervical, the second to fourth dorsals, the seventh and eighth dorsals, the eleventh dorsal.

    A physiologically weak point exists in the sacro-iliac joint in females near parturition, for the ligaments are functionally congested and softened to make dilatation and adjustment easy.