LATERAL LUXATION OF THE PATELLA. 963 



the difficulty in reduction and retention, and the less the chance of 

 recovery. Incomplete outward luxation is clearly more favourable 

 than the complete form. Meyer's cases recovered sufficiently to 

 allow the animals to be used for milking purposes. 



Symptoms. The clinical symptoms of complete dislocation 

 resemble those of crural paralysis or rupture of the extensors of 

 the stifle-joint. They consist of lameness when weight is placed 

 on the limb, with excessive flexion of all the joints. Where the patella 

 is displaced outwardly, the function of the rectus and vasti, and 

 consequently the ability to bear weight, are lost, though the muscles 

 named can still carry the limb forward. At rest, the affected leg 

 is advanced beneath the belly, and in movement the limb is carried 

 or only touches the ground. The altered position of the patella 

 produces marked prominence of the outer surface of the stifle, and 

 effaces the depression which normally exists in front of the joint. 

 The patella can be seen and felt in its abnormal position, and it can 

 be moved from side to side, when the limb is held forward. In dogs 

 the patella is readily replaced, giving immediate relief from lame- 

 ness, but soon slips out again (habitual luxation). In horses reduction 

 is more difficult. 



Treatment. As already stated, replacement proves easy in the 

 carnivora, but in all animals retention is difficult. Hertwig states 

 having kept the patella in position by hand for forty-eight hours. 

 Relays of assistants were employed, and a blister was afterwards 

 applied. As bandages cannot be used to retain the parts, treatment 

 is generally confined to rest and blistering, which compels the animal 

 to keep the foot as still as possible. Large animals should be placed 

 in slings. Recurrent luxation in the dog can be cured by section 

 of the common tendon of the patellar muscles. Luxation having 

 been reduced, the patella is held on the trochlea while the tendon is 

 subcutaneously divided close to its insertion on the bone. Aseptic 

 precautions must be observed. 



Moller saw a peculiar displacement of the patella upwards and outwards. 

 It was impossible to bend the limb, which was directed forwards, but weight 

 could very well be borne on it. When forced to move, the animal carried 

 the leg forward, holding it stiffly, and not moving the hijj, stifle, or hock 

 joints, and placed it far in advance. The progress of the body then brought 

 the limb perpendicularly under the hip-joint, but the leg could not be 

 placed behind this point, either actively or passively. Slight pressure against 

 the outer edge of the patella sufficed to return it to its position, after which 

 the horse could sometimes walk for several steps in the usual way ; 

 .suddenly, however, the patella again became displaced, and all the symptoms 

 returned. 



The post-mortem showed the inner lateral and inner and middle straight 



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