Patellar Luxation

PATELLAR LUXATION or dislocating kneecap (s) can be inherited, or acquired through trauma.  It occurs sporadically among Toy breed dogs, although it can be found in large breeds.

In dogs the patella is a small bone which protects the front of the stifle joint; it is the counterpart of the kneecap in man.  It is anchored in place by ligaments, and slides in a groove in the femur.

Conditions which predispose to patellar luxation are:  a shallow groove, weak ligaments; and mal-alignment of the tendons and muscles that straighten the joint.  The patella may slip inward (medial luxation) or outward (lateral luxation).  Luxating patellas in toy breeds are most commonly found to luxate medially.  Lateral luxation is most commonly caused by trauma, although in some cases it can also be inherited.

The signs of patellar luxation are difficulty straightening the knee; pain in the stifle; and a limp.  Often a dog with patellar luxation will look somewhat stiff in that leg because the dog is attempting to *lock* it so the patella won't move around as much.

The diagnosis is confirmed by a regular veterinarian who manipulates the stifle joint and is able to push the kneecap in and out of position without excess force.

There are 4 grades of patellar luxation:

(1) Intermittent patellar luxation causing the limb to be carried occasionally.

(2) Frequent patellar luxation which, in some cases, becomes more or less permanent.

(3) The patella is permanently luxating with torsion of the tibia and deviation of the tibial crest of between 30 degrees and 50 degrees from the cranial/caudal plane.

(4) The tibia is medially twisted and the tibial crest may show further deviation medially with the result that it lies 50 degrees to 90 degrees from the cranial/caudal plane.

Grades (1) and (2) can often be controlled by keeping the dog lean, on a good diet (supplements may help as well), and not allowing excessive jumping.  A Grade 2 can tighten to a Grade 1 and often a Grade 1 can tighten until there is no patellar luxation at all.  They can also get worse.

Grades (3) and (4) nearly always need surgery to deepen the groove and/or realign or tighten the ligaments.

Approved InfoCenter breeders have all breeding stock checked for patellar Luxation by their veterinarian before breeding.   

Any licensed veterinarian can manipulate and check for patellar Luxation.  X-rays are totally unnecessary.  All approved Premier breeders automatically supply you with copies of patellar Luxation test results of both mom AND dad. 

The following is another site that will tell you more about patellar Luxation:

www.italiangreyhound.org/patella.html

Provided with written permission from INFOSITE