Yorkie Haven Rescue is pleased to present the below article regarding Patellar Luxation which was superbly written and graciously provided by Dr. Brian S. Beale of Gulf Coast Veterinary specialists in Houston, TX. He has also written and provided us with another article about Cranial Cruciate Ligament Tears.

Yorkie Haven has entrusted all of our orthopedic cases in the Houston area to Dr. Beale's expertise. He has been a wonderful surgeon; and he and Kate Lawrence, Client/Patient Service Coordinator, have been a valuable resource for our rescue pups as well as some of our own. It is our hope that these articles will be a resource for many yorkie owners (and other breeds as well).

While a torn cranial cruciate ligament (CCL) is probably the most common orthopedic injury I see, coming in a close second 
are patellar luxations.  Patella luxation occurs when the knee cap (patella) of the patient luxates (dislocates) out of its 
position in the femoral groove.  Patella luxations are most typically seen in dogs, and usually in small breeds like 
Yorkies, Malteses, Chihuahuas, and Pomeranians, but can be diagnosed in any breed of cat or dog.

The most common type of patellar luxation is a medial patellar luxation (MPL).  This occurs when the patella luxates to the 
inside of the leg.  Less frequently, the patella will luxate laterally, or to the outside of the leg - this is called a 
lateral patellar luxation.  Patellar luxation is graded from 1-4, with grade 4 being the most severe.  The grade of luxation 
typically worsens with time.  A grade I patellar luxation can be manipulated out of position, but quickly returns to its 
normal position.  Grades II, III and IV are more severe and require surgical intervention.  With a grade II luxation, the 
patella will sometimes luxate, but can be repositioned into the femoral groove.  With a grade III patella luxation, the 
kneecap is luxated most of the time, but can be forced back into position through palpation.  A grade IV case is 
consistently luxated, and cannot be manipulated back into position.  

There are a few classic symptoms of patellar luxation.  Obviously limping is an indicator of many orthopedic problems, and 
many times patients affected by patellar luxation will be acutely non-weight bearing lame, but the non-weight bearing 
lameness will occur intermittently.  This is because when the patella is in position, the patient feels comfortable and 
ambulation is normal, however, when the patella luxates, the patient is abruptly painful and typically unwilling to use the 
affected leg.  Pet owners may see their pet "skip" when walking, or hop on one leg every few steps.  Other patients have 
been observed to stretch the affected leg behind them when standing, a posture which can sometimes manipulate the patella 
back into position.  If your pet has exhibited any of these symptoms, an evaluation by your family veterinarian, and 
possibly a consultation with a surgeon is warranted.  

Unfortunately, patellar luxation can be an inherited condition.  Other patients can experience a traumatic luxation if the 
knee is subjected to significant trauma, and still others may be due to abnormalities in the bone structure of their femur 
or tibia (the top and bottom long bones in the rear leg).  Because of these differences in causation, the treatment for 
patellar luxation involves the possibility of several different surgical procedures.  Surgical correction is performed to 
eliminate pain, prevent arthritis and decrease the chance of a future CCL rupture.  With some cases, the groove that the 
patella rides in is too shallow and must be deepened.  In other cases, a tibial tuberosity transposition (TTT) is necessary 
to adjust the placement of the patellar tendon, which is attached to the patella itself.  For patients who have a patellar 
luxation secondary to bone conformational abnormalities, the abnormal bone may need to also be corrected to prevent future 
luxation.  It is not uncommon for patellar luxations to be seen in conjunction with other orthopedic issues, such as torn 
CCL's.  These issues can typically be repaired at the same time, but are slightly more complex, and a consultation with a 
board-certified surgeon can be helpful after first visiting with your family veterinarian.  

Don't hesitate to have your family veterinarian evaluate your pet if you have seen any of the clinical signs listed above, 
or have concerns about your pet's ambulation.  Early detection is the best way to provide a good long-term prognosis for 
your pet!