Luxating Patella - Dogs and Cats

Luxating patellas is an orthopedic condition that commonly occur in cats and dogs. Luxation happens when the kneecap (patella) slips in and out of the groove (the trochlear groove) in the femur where it normally resides. A luxating patella can either be the result of an injury to the animal or result from the trochlear groove not developing properly in the immature animal. The latter case is believed to be genetic in origin. Studies have shown that as many as 82% of cases¹ in dogs are due to genetics. It is therefore a good idea not to use dogs with this condition for breeding.

The kneecap is a bone that is embedded in the tendon of the muscles in the thigh (the quadriceps), and acts like a pulley that transmits the forces of the muscles around the knee. Things to be on the lookout for that indicate that your dog might suffer from this condition:

• Your dog extends a leg for a period of time before making fast movements.
• Your dog favors a particular limb.
• Your dog is hesitant to jump up or move fast.
• Your dog often shakes a particular leg.
• Your dog "skips", that is runs while holding one leg of the ground.
• Your dog experiences sudden lameness in a limb, that quickly recovers.
• Temporary paralysis of one or multiple legs.

In my personal experience, vets pick up this condition quickly during a physical exam. Our vet told us that our pup (Tibetan x Pomeranian) will suffer from this before we even noticed the symptoms later on. Which brings me to the subject of dog breeds that are more susceptible to this condition. Generally these are the smaller breeds, that often include these common breeds:

• Boston Terrier
• Cavalier King Charles Spaniel
• Chihuahua
• Jack Russel Terrier
• Maltese
• Pomeranian
• Yorkshire Terrier

In larger breeds this condition is more likely to occur due to injury or of a result of other structural problems, such as hip dysplasia. Although less prevalent, I understand that this condition can occur in cats as well. I have never seen this condition in a cat, but breeds that are apparently susceptible is the Devon Rex and Abyssinian cats.

Treatment of severe (high grade) cases, generally require surgery. For the less severe cases it is generally recommended to keep your dog fit and healthy condition, and feeding it a diet high in omega fatty acids (which is recommended for dogs with any skeletal problems). Although it may be considered anecdotal evidence, I can attest that our Tibetan x Pomeranian cross has largely overcome this problem. He is extremely fit on account of being an obsessive ball chaser, and also enjoys the great meals we supply.

If the reader would indulge me in some scientifically unvalidated speculation, I would like to proffer an hypothesis regarding the occurrence of this condition. Given that it appears that the depth of the trochlear groove is developed in the growing, immature animal and that the prevalence of this condition is found, in what is generally considered as "toy breeds", I believe that a lack of exercise during the formative stage of the animal could either cause or exacerbate the condition in these animals.

[1] Hayes AG, Boudrieau RJ, Hungerford LL. Frequency and distribution of medial and lateral patellar luxation in dogs: 124 cases (1982-1992). JAVMA 1994;205(5):716-720.

[2] Image available under CC-BYSA 3.0 which is a derivative work of contributors Florian Scheuerer, and A.Spielhoff, via WikiMedia Commons