UPWARD LUXATION OF THE PATELLA. 
690 
or to others after passing through severe attacks like influenza. Not 
infrequently such elongation is congenital. Loose-jointed, weak foals with 
straight stifles suffer oftener than well-developed horses. Fixation of the 
patella on the upper portion of the internal lip of the trochlea is at once 
followed by extension of all the joints of the limb and inability to flex them, 
even with external assistance. The limb is therefore stiffly directed back¬ 
wards, and cannot be advanced. If both limbs are affected at the same 
time, the animal stands as though rooted to the spot and cannot 
advance, when only one limb is affected, it can still hop forwards on 
the other leg. Luxation is, therefore, distinguished by lameness when 
the leg is carried and excessive extension of all joints. 
If, whilst the patella occupies this position, the rectus and vasti 
muscles be relaxed, the patella may rise from the lip of the trochlea of 
the femur and stand upright on its lower border, a condition which in 
man is known as vertical luxation of the patella. The symptoms are so 
characteristic that stationary luxation can be diagnosed from a distance, 
and is only likely to be mistaken for dislocation of the biceps femoris 
muscle in oxen, in which, however, the extended position is not so well 
marked, and the limb can always be flexed, if only to a slight extent, 
while the trochanter may be felt under the skin, and the patella at least 
moved sideways. In luxation, on the other hand, it is absolutely 
immovable, and lies too high. 
The prognosis depends partly on the amount of interference with 
movement, and therefore with usefulness, partly on the character of the 
lameness, the age of the animal, and the length of time the condition has 
existed. In weakly foals, and in animals attacked during convalescence, 
both momentary and permanent luxation usually cease to occur as the 
general condition improves. The longer, however, lameness has existed, 
and the more frequent and marked the attacks, the slighter is the chance 
of recovery. 
Treatment. Young animals and convalescents should he well fed 
and kept fiom heavy work. With rest and the recumbent position, the 
straight ligaments of the patella return to their normal length. Every¬ 
thing likely to cause 1 elapse must be avoided. In momentary luxation 
nothing fuither can usually be done, but stationary luxation calls for 
immediate 1 eduction, which may be effected m one of several ways. 
(1) I he patella often returns to its proper position after sudden 
backward or side movements. Energetic contraction in the patellar 
muscles, produced by an unexpected blow or by drenching the animal 
with cold water, also induce reduction at times. 
(2) Where the above means prove insufficient, an attempt should be 
made to free the lower edge of the patella by pressing on its upper and 
outer border, the pressure being directed forwards, and inwards. 
