What Are Luxating Patellas?

If you have been a dog owner for any length of time, you've likely had a dog with a luxated patella, or knew someone who did.  The "patella" is the knee cap.  There are 2 different kinds of patellar luxations.  Dogs of all sizes and breeds can have this condition,  and so can cats, though it's more rare. 

There are medial luxations and lateral ones.  Medial means the knee 'pops out' towards the inside of their body, and lateral means the knee will pop out towards the outside. 

Medial luxations tend to happen early in life and are often considered to be congenital.  Often there are anatomical malformations which cause this to happen.  Without too many boring details, it can be defects in the way the leg bones were already formed when they were born.   These malformations put undo stress on the knee and it's surrounding components, which leads to the ligaments holding everything in place to rupture.  Young and mature animals with gait problems may be predisposed.  In general, any time you notice a strange conformation to their walk, it should always be looked at by your vet.

Laterally luxating patellas can be worse than medial ones.  They tend to limit movement a little bit more.  This can occur in small breeds later in life, due to the natural degeneration of surrounding tissues.  Lateral luxation may be seen more in dogs predisposed to hip dysplasia.  The abnormalities in the bones which cause hip dysplasia may cause the animal's lower limb to rotate to compensate, causing this as a secondary condition.  If this occurs bilaterally, your animal may be unable to stand.  (More on Hip Dysplasia)

While your vet may use radiography to diagnose, often your vet can tell by just feeling their knee and shifting it around.  There is a very specific way it *shouldn't* move!  One veterinarian told me that radiographs are more diagnostic of the bone malformations which have caused the patella to luxate, and often you cannot see the knee cap luxated in a radiograph. 

You can see the limping, or non-weight bearing behavior come and go.  The first time my dog limped and pulled his leg up, I checked his paws to see if he had something stuck.  When he put his leg back down, he walked fine again.  It took a couple more times before I knew for sure something was wrong.  Though I have never x-rayed my dog, I feel strongly his luxations were caused by his hip dysplasia.  When I first got him, I could tell he moved awkwardly and showed a lot of stiffness in his hips.  At the vet, only one was laterally luxating at the time.  Now, both luxate.  He has a severe heart condition that may take his life sooner than later, so surgery is not an option for him.  He is on an NSAID, and I rarely notice them popping out.  When they do, I am able to move them back into place and he walks fine.

I had a cat with a luxated patella, and we started noticing it later in her life.  Surgery became a consideration, but it was only shortly thereafter she passed away from causes related to old age.

Surgery is the treatment.  There are many amazing surgeons for dogs in this area, and I've seen dogs recover from surgery and do just amazing!  Prognosis may vary from dog to dog based on level of activity, age, etc.  Every animal is different!  This condition is not uncommon, and if it were me, I wouldn't think twice about adopting a dog whose had surgery to correct this condition.  It's also a consideration, like all medical expenses, for anyone adopting a new dog. The last question one may have, is if they can prevent this from happening.  That is a question best answered by your veterinarian.  There are varying degrees of the conditions which may predispose your animal.  For instance, there are varying degrees of severity with hip dysplasia which may predispose your pet.  I have personally known just as many small dogs get this condition, and I'd be cautious to send anyone away thinking this is a disease of a certain breed or size.