The patella, or kneecap, is part of the stifle joint (knee). In patellar luxation, the kneecap luxates, or pops out of place, either in a medial or lateral position.

Medial patellar luxation should be considered an inherited disease and is often seen in puppies. Lateral patellar luxation’s heritability is unknown. It is usually seen later in life, around 5-8 years.


Bilateral involvement is most common, but unilateral is not uncommon. Animals can be affected by the time they are 8 weeks of age. The most notable finding is a knock-knee stance. The patella is usually reducible, and laxity of the medial collateral ligament may be evident. The medial retinacular tissues of the stifle joint are often thickened, and the foot can be seen to twist laterally as weight is placed on the limb.

Medial Luxation signs include abnormal hind-leg carriage and function, and/or sudden signs of lameness. Signs vary dramatically with the degree of luxation. In grades 1 and 2, lameness is evident only when the patella is in the luxated position. The leg is carried with the stifle joint flexed but may be touched to the ground every third or fourth step at fast gaits. Grade 3 and 4 animals exhibit a crouching, bowlegged stance with the feet turned inward and most of the weight transferred to the front legs. Permanent luxation renders the quadriceps ineffective in extending the stifle. Pain is present in some cases. Most animals, however, seem to show little irritation upon palpation.

Lateral Luxation signs may develop rapidly and may be associated with minor trauma or strenuous activity. A knock-knee stance, sometimes described as seal-like, is characteristic. Sudden bilateral luxation may render the animal unable to stand and simulate neurological disease.


Correction may only be accomplished using orthopedic surgery and is traditionally only recommended for higher grades of patellar luxation (grades 3 – 5). Assistance for dogs with patella luxation can include the use of pet ramps, stairs, or steps. This will prevent additional pain and damage to the patella.

Test method

The dog undergoes a physical examination while awake (chemical restraint is not recommended) and classified by the attending veterinarian according to the application and general information instructions. The veterinarian then completes the OFA application form indicating the results of the dog’s patella evaluation.

The application and fee can then be mailed to OFA. The attending veterinarian and owner are encouraged to submit all evaluations, whether normal or abnormal, for the purpose of completeness of data. There is no OFA fee for entering an abnormal evaluation of the patella in the data bank.

 Genetic/breeder information

Evaluation of dogs under 12 months of age is encouraged if the owner desires to breed at this age. The most opportune time to gather breeding data is at 6-8 weeks of age prior to the puppy’s release to the new owner.

A breed database number will be issued to all dogs found to be normal at 12 months of age or older. The breed database number will contain the age at evaluation and it is recommended that dogs be periodically re-examined as some luxations will not be evident until later in life.

 Stats within CdT breed

From 1974 – 2012 there were 1316 patella evaluations submitted to the OFA. 95% of them were normal; 5% were abnormal.

 Source of data