laxation has been complete and the patient lying on a hard table which can not adapt itself to the shape of the back, the lumbar spine sags greatly, and it is in this way that the great majority of postoperative backaches are explained. Such backaches are easily controlled by supporting the lumbar spine with a pillow, and holding firmly together the sacro-iliac articulations with a belt, bandage or adhesive strapping. Backaches occur in the same manner in acute illnesses where the general muscular system becomes relaxed and the individual, lying largely on the back, the lumbar spine is permitted to sag.

The same condition of affairs occurs from long sitting if the body is not held erect but is permitted to "slouch," the lumbar spine becomes flexed, carrying the base of the sacrum backward and straining the sacro-iliac ligaments.

In all these conditions previously described, excepting the toxic inflammations, there has been no actual damage done the joints. The condition of strain and accompanying symptoms have been relieved with change of position. If, however, strain is continued until the bones are displaced, or if the strain be sudden and sufficiently severe to lacerate some of the ligaments, we have a true sprain, accompanied by a sharp pain or "stitch" in the back, with the pain ofttimes referred to one or the other of the sacro-iliac joints. Lumbago is very often simply a manifestation of a sprain of a sacro-iliac joint.

When a sprain with displacement occurs, the displacement is often reduced when the correct attitude is assumed. But if the small irregularities on the articular surfaces of the sacrum and the ilia catch, then manipulation may be necessary for reduction.

Again, if the deforming force be moderate in severity and continued over a long period of time, a condition

of "chronic relaxation" is reached, with or without displacement. Great discomfort and disability occur in this condition incident to the instability of the pelvis, due to relaxation of the sacro-iliac ligaments. The attachment of the thigh and trunk muscles to the pelvis, explains any disability that may occur in such a condition.

The sacral plexus of nerves containing branches from the lumbar plexus is situated just in front of the sacroiliac articulations, and it is obvious that strain or displacement of these joints may produce irritation in the nerve trunks situated anteriorly to them. The symptoms resulting in this way are dependent on the nerve trunks injured and the severity of the injury. In this way, also, referred pains in the lower extremities and areas of anesthesia and hyperesthesia are explained. Of greater importance, however, are obstinate sciaticas which, in the vast majority of cases, are due to irritation produced by the sacro-iliac synchondroses. Dr. Goldthwait tells me that nine cases out of every ten of sciatica are produced in this way, and its importance as regards treatment is quite evident. He states that many cases of sciatica can not be cured unless the sacro-iliac joints are properly treated. Since it is a well-established fact that when a nerve is injured, pain is referred to its distribution and not to the seat of injury, the futility of treatment applied to the seat of pain is quite evident.

When displacement occurs, it is most often backward with reference to the upper part of the sacrum. In acute conditions this displacement is usually unilateral, while in the cases of long-standing "chronic relaxation," both articulations are involved resulting in the flat back so commonly seen.

Forward displacement of the sacrum, however, is possible, and in falling from great heights and striking on

the feet, it may actually be driven downward with the ilia raised and the legs apparently shortened.

Nerve irritation with referred pain is most common in cases of sudden unilateral displacement. The pain may vary from a slight twinge to one severe in character. When the relaxation is slow and the displacement is gradual, the nerve trunks adapt themselves to these changes and referred pain is not so common.

Of the infectious processes occurring in these joints, the nontubercular are more common than the tubercular, though both are very rare. Toxic inflammations, however, are quite common, the resultant damage varying from a few adhesions to complete ankylosis. Toxic inflammation may occur as a part of a general polyarticular involvement.

Proper attitude is dependent on normal muscular tone and the security of the base to which the trunk muscles are attached. If this be true, it is evident that with an insecure pelvis, correct posture can not be assumed without undue muscular effort. With a pelvic girdle whose joints are relaxed, the body droops forward, in which condition the support given the abdominal viscera by the trunk muscles is removed and the abdominal organs sag. In the treatment of these various ptoses due consideration must be accorded the pelvic girdle if the ligaments which hold it secure are relaxed or if, for any reason, it be insecure.

SYMPTOMS.

The most important symptom to be considered in the diagnosis of this condition is limitation of motion. If the sacro-iliac joints be diseased or strained, any motion which causes strain will be limited involuntarily, as is exactly the case with other joints of the body when diseased. In the case of the sacro-iliac joints, limitation of

motion may be shown by motions of the body on the thighs, or by motions of the thighs on the body. If the knees be held stiff and the body bent forward, the amount of forward bending will be limited if the sacroiliac joints be at fault. This motion is made by the hips and spine up to the point where the hamstring muscles become tense, then it is made by the sacro-iliac joints, hips and spine. When the hamstring muscles become tight and strain is put on the irritable sacro-iliac articulations, the spinal muscles are thrown into reflex contraction and the motion is limited.

The way in which to determine whether this forward limitation of motion is due to the synchondroses or to the spine, is to relieve the tension on the hamstring muscles by permitting the patient to sit, when forward bending will be much freer.

When forward bending is limited, lateral bending is likewise affected, and since one side is usually more. affected than the other, a difference will exist between the amount of bending toward the two sides. In standing there will often be a marked lateral deviation of the body away from the affected side. Since the hamstring muscles play no part in lateral bending, no difference is noted whether the patient assume the sitting or standing posture.

Backward bending is usually very guarded, and cases where the body is thrown forward and held in that position, backward bending is, of course, impossible.

These tests can also be carried out under conditions in which the sacro-iliac joints do not carry the body weight. To accomplish this, the patient lies on his back. Instead of forward bending, the legs are raised, the knees being held stiff. For lateral bending the legs are abducted and for backward bending the patient lies on the

face and the legs are hyperextended. With the patient lying on the back with the knee bent, all normal motions will be unlimited and painless unless the joint be very sensitive, or unless extremes of motions be carried out; outward rotation and abduction are then usually painful.

If only one joint be involved, straight leg raising will be limited on both sides though, naturally, not so much so on the unaffected side. Pain will also be referred to the affected side no matter which side is raised. The explanation of this is that when the leg on. the unaffected side is raised, the hamstring muscles become tense and move the ilium on that side, naturally the sacrum is carried with it and consequently we have motion also on the affected side.

Pain-With the exception of limitation of motion, pain is the most important diagnostic symptom in this malady. Pain may be referred directly to the sacroiliac joints, but more often to the sacral region, also to the leg and foot. The pain which is referred to the leg and foot may be localized in definite areas. In these cases, pressure over the nerve course elicits no pain, a differential diagnostic point from neuritis.

The pain present is usually worse at night, dependent upon the increased strain which results from recumbency, and is also made worse by any motion or position which increases strain.

In the case of children, the pain most usually takes the form of legache or backache. While it may be present during the day, it is almost always present at night, and is frequently mistaken for so-called growing pains, and sometimes confused with the night cries of tuberculous hip disease.

Swelling-There is rarely ever swelling in sacro-iliac