Luxating patella, sometimes called patellar luxation, floating kneecap, or trick knee, is a common issue in the Yorkshire terrier breed.
Luxating patella is when the kneecap luxes, or pops out of place. Luxating patella can either be a result of inherited traits or be the result of an injury. In Yorkies, this luxation is generally an inherited condition. While the luxation may not be present at birth or at an early age, the anatomical abnormalities that lead to a patellar luxation are present at birth in cases where the luxation is inherited.
According to the Orthopedic Foundation for Animals, of dogs tested for patellar luxation between 1974 and 2012 (449 Yorkies reported to OFA), the Yorkshire terrier is the breed with the second highest incidence of luxating patella. The OFA data shows that of Yorkies tested, 24.9% have some sort of luxating patella. With a quarter of the sample population of Yorkies being affected, luxating patella is a common medical condition in the breed.
Since most Yorkie owners don’t have x-ray vision or years of veterinary training, it’s important for every Yorkie owner to know the signs and symptoms of luxating patella. The symptoms can vary widely, depending on the severity of the condition (we will get to that in a minute). Dogs only have patellas on the hind legs, so the symptoms pertain to the rear legs only. Symptoms can include:
- abnormal carriage of the hind legs
- intermittent abnormal gait
- lameness or difficulty walking
- bowlegged stance
- “skipping” when running
- pain when walking or leg being touched
Many of these symptoms can be indicative of other things too, so if you suspect that your Yorkie has luxating patella, make an appointment with your veterinarian.
In order to diagnose luxating patella, your vet will examine your Yorkie. The examination is done by feeling the legs, and luxating patella can be diagnosed without any x-rays or imaging studies. Upon examination, your vet will determine whether or not your Yorkie has luxating patella and if so, the severity of the condition. There are four grades of luxating patella, with grade I being the least serious and grade IV being the most severe. Here are descriptions of the grades:
Animals in this group have a patella that can be luxated manually but returns to its normal position within the trochlear groove when released.
This group includes animals in whom the patella can be luxated manually or those animals in whom stifle flexion with or without internal rotation of the tibia will cause luxation of the patella. The patella once luxated remains so until it is replaced manually.
In this group of animals the patella remains luxated most of the time. It can be reduced manually but will reluxate when the manual pressure of reduction is removed.
In this group of animals the patella will be luxated all the time and manual reduction of the patella within the groove will be impossible even with the leg in full extension.
Grades I and II, sometimes even grade III, are typically treated with rest and pain relievers, sometimes with stabilization. Your general veterinarian can diagnose and treat the less severe cases. The prognosis is good in these categories and most dogs with grades I and II luxations live happy, fully-functional, and relatively pain-free lives. The prognosis is typically even better for young, otherwise healthy dogs. In more severe cases, surgical options are available. Your veterinarian may refer you to an orthopedic surgical specialist. There are many different types of surgeries, depending on the type of patellar luxation. The likelihood of a successful prognosis is increased as the severity of the symptoms decreases. In effect, the less severe the symptoms, the greater chance of a return to full functioning after surgery. Additionally, the younger the Yorkie is, the greater the chance of a more successful outcome.
So, what can you do to prevent luxating patella? Since most Yorkies with luxating patella inherited the abnormalities that led to their condition, you can prevent further damage to the soft tissue that hold the patella in place. This can help to delay the effects of luxating patella or prevent them from becoming problematic. Do what you can to strengthen and reduce stress to your Yorkie’s joints. This may mean furniture stairs (prevents jumping off the couch, bed, etc which shocks the joints), keeping your Yorkie at a healthy weight, eliminating slippery floors, joint supplements, a diet rich in essential fatty acids, or a combination of these.
If you are considering adding a Yorkie to your family and want to know what you can do to find a Yorkie with less of a chance of having luxating patella, you can ask for the test results of your potential puppy’s parents. Since patellar luxation is inherited, responsible breeders have their dogs tested. Not all breeders submit their testing information to the OFA, but if they do, you can ask for a copy of the OFA certificates for the puppy’s parents. Some breeders go the extra step and have their dogs CHIC certified (tested for luxating patella, eye disease, and are microchipped). You can search the CHIC database to find out the parents’ medical information, if it has been submitted. There are over 200 Yorkies currently in the CHIC database. When I registered my man, Mr. McKeever in 2009, there were only 18, so the CHIC database is growing. If you want to see an example of the information, you can check out Mr. McKeever’s CHIC profile here. In general practice, I have not seen a responsible breeder breed a Yorkie with anything greater than a grade II luxation, and many will not breed any dog with anything greater than a grade I. Still, even if both parents have normal patellas, it is possible for their offspring to have the condition.
Now you know a little more about luxating patella. If you’d like to read more, you can visit the OFA’s website for more information. Orthopedic Foundation for Animals