LUXATION OF THE PATELLA. 



439 



home perfectly sound. Next morning it was unable to walk, or even 

 to move over m its stall. 



State on Examinatiun. — The animal had much difficulty in backing 

 out of its stall, and when pushed into the yard stood in the position 

 shown in Fig. 55. 



The off hind leg was extended and placed stiffly under the body, 

 with the toe pointing somewhat outwards. The stifle and hock joints 

 were perfectly rigid, and resisted all attempts at flexion. When the 

 mare was walked forwards the limb gradually became upright, rotating 

 around the toe as a flxed point, but as it neared the perpendicular the 

 fetlock was flexed more and more, until finally it assumed the position 

 shown in Fig. 56, the front of the hoof then forming an angle of about 

 15° to 20° with the ground, the metatarsus and tibia being nearly vertical, 

 the limb as a whole inclined outwards, and the bod}- leaning towards 

 the near side. This seemed the critical angle ; an}- further forward 

 movement was followed by the leg escaping, describing a semicircular 

 sweep, and returning to the position of Fig. 55. There was no par- 

 ticular distress in moving forward, 

 though it was difficult ; but move- 

 ment in a backward direction was 

 almost impossible. As the animal 

 could not place the off hind leg 

 any further behind it than is shown 

 in the second of the two figures, 

 movement in this direction was 

 accomplished by crouching down 

 nearly on to the hocks, rotating 

 the body on the near hind leg, 

 thus dragging back the on" hind, 

 then rising, taking weight on the 

 off hind, and retiring the near 

 hind. The same process was re- 

 peated at each step. 



The peculiar rigidity of the 

 limb at once suggested luxation of 



the patella, and by thrusting the bone inwards and downwards the 

 writer succeeded m reducing the condition, replacement occurring 

 with a sudden click and spasmodic flexion of the limb similar to that 

 in stringhalt. The animal could then walk forwards in a straight line 

 or move backwards without difficulty, but immediately it essayed to 

 turn the patella again became displaced, and had to be assisted into 

 position. In all the dislocation was reduced five times on the first 

 day. It was difficult to distinguish any marked difference in the shape 

 of the two stifles, though the displaced patella formed a somewhat 

 more prominent mark on the outer aspect of the stifle, and was rather 

 higher in position than usual. 



The patient was placed in slings, the leg drawn forward and fixed 

 to the girth, and the luxation finally reduced. 



The animal soon slipped out of the slings, and when returned 

 hung with its whole weight in them, so that it had to be released. 



^00. 



Fig. 55. 



