OFA Patellar Luxation Number. Patellar Luxation is, in essence, how much unusual slipping exists in the dog's kneecap. The OFA Patellar Luxation Number on your dog's certificate will be in this format: AS-PA123/28M-T. Here is how to interpret this number. AS = Breed Abbreviation (Australian Shepherd, in this example) PA = Test (Patellar Luxation) 123 = Certification number 28 = Dog's Age in Months M = Dog's Gender T = The dog has a permanent ID, such as a tattoo or microchip The Patellar Luxation number does not show the results, so owners must consult the OFA report for the results. Patellar Luxation results may include: Normal - No unusual slippage. Grade 1 - Luxation is minimal, and returns to the trochlea, or the groove where the kneecap normally rests when released. Grade 2 - Frequent patellar luxation, which may become permanent in some cases. Dogs may live with Grade 2 patellar luxation for many years, but over time the articulating surface of the patella and the proximal area of the medial lip may become worn. Dogs with Grade 2 may require surgery after years of living with this condition. Vets who certify puppies as healthy and sellable in pet shops typically accept Grade 2 patellar luxation as certifiably healthy, although it's a clear indicator of potential health problems later in the dog's life. Grade 3 - Indicates a patella permanently luxated. Surgery may correct this problem, or the limb may be used in a semi-flexed position. Grade 4 - A patella permanently luxated. The limb is carried, or the dog may move in a crouched position with the limb flexed. Patellar luxation is a condition wherein the dog's kneecap pops out of place, due in part to a malformed bone structure in the knee. Luxation is suspected to be an inherited condition, and dogs with lateral luxation or medial luxation (but not luxation caused by an injury) should not enter into a breeding program. Patellar luxation is a newer genetic health condition, and fewer breeders test for this condition.