Editor’s Note: The following piece on luxating patellas, a medical issue that can affect cockapoos, was contributed by Cristine Smith at Shady Lanes Kennel.

What is it?

Patella luxation simply means the knee cap dislocates from its normal position. The most common reason for this issue is due to the patellar ligament that runs from the bottom of the kneecap to the tibia (shinbone) is attached in the wrong place, therefore putting pressure on the kneecap that causes it to move from its groove in the femur (thighbone).

Can it be prevented?

This is a very common congenital defect in many small canine breeds, however responsible breeders have their breeding stock tested and certified by OFA (Orthopedic Foundation for Animals) to assure they are not using parents with this problem and producing puppies with this defect. Unfortunately it is possible for certified parents to have off spring with slight patella luxation but the severity is greatly decreased.

How is it detected?

You may notice your running dog yelp, hold up a rear leg, and limp, but within minutes be fine again. You may also notice a bowlegged stance and in severe cases you can actually see the leg pop out of line as the dog is trotting. The yelp and lameness may not happen every time they are playing and therefore less likely to be mentioned at the next vet visit. Your veterinarian should include a patella exam during his/her annual physical and if you are not sure its been done then dont hesitate to ask. The vet will simply manipulate the rear legs to feel if the patella moves out of its location. The severity of the condition is graded from 1 to 4.  The following is the official grading system from the OFA:

Grade One = The patella easily luxates manually at full extension of the stifle joint (knee), but returns to the trochlea (groove in the knee joint) when released.

Grade Two = There is frequent patellar luxation which, in some cases becomes more or less permanent.

Grade Three = The patella is permanently luxated with torsion of the tibia and deviation of the tibial crest of between 30 degrees and 50 degrees from the cranial/caudal plane.

Grade Four = 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.

Here is a diagram of a normal dog knee and one suffering from patella luxation.