SYNOVITIS OF THE SHOULDEE. 129 



fully distend it in the adult. In consequence of the increase of 

 fluid, all the natural depressions about a joint become obliterated, 

 or even converted into elevations, and thus the outline of the 

 limits of the synovial membrane becomes apparent. 



Joints of the Upper Extremity. Sterno-Clavicular. Owing 

 to the weakness of the anterior ligament, fluid in this joint shews 

 itself by a distinct prominence over the front of the joint. 



Shoulder-joint. When distended with fluid the bony surfaces 

 may be appreciably separated, owing to the laxness of the capsule, 

 the rotundity of the deltoid is increased, the elbow is carried a 

 little backward and humerus rotated internally, and thus a slight 

 lengthening of the arm may be demonstrated. The hollow groove 

 between the pectoralis major and the deltoid is obliterated, and 

 fluctuation may be determined by manipulation of that part of 

 the capsule which may be felt in the axilla. 



There are three diverticula of the synovial membrane of 

 the shoulder, all in connection with tendons. Beneath the 

 subscapularis in front and to the inner side, around the long 

 tendon of the biceps for some distance down the bicipital groove 

 anteriorly, and beneath the infraspinatus near its insertion 

 behind. All of these become distended with fluid in synovitis. 



In suppurative synovitis pus may track along any one of these 

 pouches. If it escapes by the subclavicular route, it may spread 

 between the subscapularis and the venter of the scapula. When 

 it leaves the joint cavity by the bicipital groove, it may ultimately 

 appear at the lower and anterior border of the deltoid. Escaping 

 behind the joint, purulent fluid nearly always progresses forwards 

 towards the anterior aspect of the limb, this being the path of 

 least resistance owing to the denseness of the fascia covering the 

 deltoid. 



Elbow-joint. The elbow- joint when filled with fluid, as the 

 result of inflammation, loses most of its natural contour, and all 

 the guiding bony points become greatly obscured. The oblitera- 

 tion of the fossae on either side of the olecranon process is very 

 marked, and readily indicates the existence of synovitis. 



Pus within the joint as a rule finds its way to the surface about 



C.A.A. 9 



