The OFA patella evaluation for breeding dogs
A skipping back leg is so common in small dogs that many owners think it is normal. It is not. A slipping kneecap is inherited, and one short exam can find it. This VerifiedStuds guide explains the test, the grades and what a breeder should do with the result.
The patella is the kneecap. Normally it glides in a groove at the end of the thigh bone. In a dog with patellar luxation, it slips out of that groove, either toward the inside of the leg or toward the outside.
For an OFA patella evaluation, a veterinarian feels each knee by hand while the dog stands and while the vet moves the leg. The exam needs no x-ray or sedation. Then the vet records the findings on an OFA form, and the result goes into the public database.
Grade
What the vet finds
Typical signs
Normal
The kneecap cannot be pushed out of place
None
1
It can be pushed out by hand but returns at once
Usually none
2
It slips out on its own at times and returns
An occasional skip or hop
3
It sits out most of the time but can be pushed back
Frequent lameness, a crouched stance
4
It is out permanently and cannot be replaced
Severe lameness and bowed legs
Only a normal result receives an OFA patella number. Any grade from 1 to 4 means the dog has patellar luxation. In addition, the form records which knee has the problem and in which direction the kneecap moves.
Luxation is most common in toy and small breeds, where the kneecap usually slips inward. Therefore, it appears on many of their health lists:
Toy breeds: Pomeranian, Yorkshire Terrier, Chihuahua, Toy Poodle and Cavalier King Charles Spaniel.
Small companion breeds: French Bulldog, Boston Terrier and Miniature Poodle.
Some larger breeds too: for example, the Cane Corso, Mastiff and Chinese Shar-Pei.
See the health testing guides for your breed, including Pomeranian health testing and Yorkshire Terrier health testing.
OFA issues a patella number from 12 months of age. Before that, a vet can still examine the knees and give a preliminary opinion. However, luxation sometimes develops as a dog matures, so a puppy exam is not final.
For the same reason, many breeders recheck the knees every year or two while a dog is in a breeding program. Vets avoid examining a female while she is in heat or heavily pregnant, because hormones loosen the ligaments.
Dogs inherit patellar luxation, although several genes play a part. As a result, the standard advice is clear: breed only dogs with normal knees. A dog with any grade of luxation can pass on the tendency, even if it never limps.
Still, no result is a guarantee. Two normal parents can produce an affected puppy. So look at relatives as well. Knees that are normal across parents, siblings and earlier puppies are the strongest evidence you can find.
This is one of the cheapest health tests. Vets often do it during a routine visit, so you pay the office fee plus OFA's small registration fee. Health clinics at dog shows are usually cheaper again. Ask your vet for a quote.
Search his registered name on the OFA website.
Find the patella line on his record, and check that it reads normal.
Look at his age at the exam. Twelve months or older is a real clearance.
Watch him move. A skip, a hop or a bow-legged stance is worth a question.
Ask about his puppies. For instance, have any needed knee surgery?
The kneecap is one line on a breed's list. Read what is a CHIC number to see how the whole list fits together. Then find a health-tested stud, and compare prices in the stud fee guide. Stud owners can list their stud free. This page is general information, not veterinary advice.
What is a luxating patella?
It is a kneecap that slips out of its groove. Vets grade it from 1, the mildest, to 4, the most severe.
At what age can a dog get an OFA patella number?
From 12 months. Earlier exams are preliminary.
Does an OFA patella evaluation need x-rays?
No. A veterinarian checks the knees by hand, usually without sedation.
Can a dog with a grade 1 luxating patella be bred?
It is not advised. Any grade means luxation is present, and the tendency is inherited.
Is a patella clearance valid for life?
The number stays on the record. However, many breeders repeat the exam, because luxation can develop later.
Sources: Orthopedic Foundation for Animals, patellar luxation, Orthopedic Foundation for Animals, CHIC program, American Kennel Club, breed health testing requirements.
Every profile shows his results, and you can verify them on OFA.