692 
LATERAL LUXATION OF THE PATELLA. 
condition often appears in both limbs. Another factor may consist in 
relaxation and weakness of the ligaments. In dogs the inner lateral 
ligament is much slighter than the outer. 
Everything favouring rupture or strain of the internal lateral ligament 
may produce the condition. Meyer believed it was caused by rheumatic 
contraction in, or excessive action of the abductors, but failed to effect a 
cure by dividing them. 
The prognosis is less favourable than in upward luxation, particularly 
in dogs. Pugs often suffer congenitally, and little can be done for them. 
As in other cases, the older the luxation the greater 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 and 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 
advance the limb, the stride being somewhat shortened. The capsular 
ligament appears distinctly below the stifle, whilst the patella can often 
be felt in its abnormal position. The symptoms are less marked in 
incomplete luxation, in which lameness is sometimes more pronounced 
when walking than when trotting. 
In dogs the patella is readily replaced, giving immediate relief from 
lameness, but soon slips out again (habitual luxation). In horses reduc¬ 
tion is more difficult, and the limb is afterwards held stiffly, and only 
slowly advanced. 
Treatment. As already stated, replacement proves easy in the 
carnivora, but in all kinds of 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 can be slung. 
Moller saw a peculiar displacement of the patella upwards and outwards. 
It was impossible to bend the limb, which was extended and 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 hip, 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 
