LAMENESS IN THE HIND LEG 215 



due to a weakened condition of the patellar ligaments or spas- 

 modic contraction of the crural muscles. 



In upward luxation, reduction is effected by attempting fur- 

 ther extension of the stitie joint and at the same time the patella 

 is pulled outward, off the internal rim of the trochlea. This is 

 attempted by securing the subject in a standing position; the 

 sound side is kept against a wall if possible and a rope is tied 

 to the extremity of the affected leg. Traction is exerted upon 

 tile rope and at the same time force is directed against the stifle 

 joint to produce further extension if possible, so that the straight 

 patellar ligaments may relax sufficiently to allow the patella to 

 be dislodged from its position upon the inner trochlear lip. Fail- 

 ing in this manner of procedure, the affected animal is to be 

 cast and anesthetized with chloroform. The relaxation which 

 attends surgical anesthesia will permit of reduction of the dis- 

 located bone and uuuiipulations such as have just been outlined 

 may be employed. 



Following reduction in the average case it is essential that the 

 subject be given vigorous exercise for a few minutes. Reduction 

 having been affected, the application of a vesicant over the 

 whole patellar region is customary. 



In cases of habitual luxation, unless the ligaments are so lax 

 that the patella may be displaced laterally over the inner as 

 well as the outer trochler rims, division of the inner straight 

 patellar ligament will correct the condition. This desmotomy 

 has been advocated by Bassi, and good results in appropriate 

 cases have been reported by Cadiot, Merillat and Schumacher. 

 This operation has been found a corrective in cases of outward 

 luxation as well as those of upward dislocation of the patella 

 when resorted to before the trochleae are worn from frequent 

 luxation. 



Outward luxation of the patella is occasioned by a lax condi- 

 tion of the internal femeropatellar ligament or a rupture of the 

 same so that the patella slips over the outer femoral trochlear 

 rim and permits of an abnormal flexion of the stifle joint. The 

 outer trochlear rim being the smaller of the two, inward luxation 

 does not occur in the horse. With the patella disarticulated in 



