The Orthopedic Foundation For Animals, Inc.



What is Hip Dysplasia?

How Prevalent is it?

Recommended Breeding Principles

AVMA Positioning Required

Radiographic Criteria



OFA Number Interpretation

Correction of Anecdotal Misinformation


The purposes of the registry are: to provide a standardized evaluation for hip dysplasia and to serve as a database for control of hip dysplasia through selective breeding. To date the OFA maintains the world's largest data base on hip conformation.

What is Hip Dysplasia?

Canine Hip Dysplasia (CHD) is an inherited trait involving multiple gene pairs which results in a spectrum of radiographic conformations. CHD is a developmental disease. All dogs apparently are born with normal hips but in affected individuals the radiographic signs of CHD can become evident within several months to several years. Therefore, the accuracy of diagnosis increases with age to about 95% at 24 months of age. OFA preliminary evaluations (dogs evaluated between 4 and 23 months of age) are about 90% accurate when compared to repeat studies at 2 years of age.

How Prevalent Is It?

The incidence of dysplasia in a given breed is unknown. The majority of dogs evaluated by the OFA are submitted by breeder clientele concerned with controlling CHD. Therefore the OFA data, while biased toward normal due to prior screening by referring veterinarians, can serve as a benchmark for the frequency of CHD in the breeding population (Table 1). The incidence of CHD is breed dependent and improvement depends on responsible breeding practices. It has been demonstrated that the frequency of CHD can be reduced by responsible selective breeding practices (Table 2).

Recommended Breeding Principles

  1. Breed normals to normals.
  2. Breed normals with normal ancestry.
  3. Breed normals from litters with a low incidence of CHD.
  4. Select a sire that produces a low incidence of CHD.
  5. Replace dogs with dogs that are better than the breed average.

AVMA Positioning Required

The OFA requires a ventrodorsal radiograph with the pelvis symmetrical, femurs parallel to one another and approximately parallel to the table, and with the patella on the midline. The radiographic technique should be sufficient so that the trabecular bone pattern and the dorsal rim of the acetabulum can be seen.

Radiographic Criteria

All radiographs are screened for positioning and technique upon arrival. If the radiograph is not diagnostic it is returned to the referring veterinarian.

Acceptable radiographs are then evaluated independently by 3 board certified veterinary radiologists and a consensus derived.

The hips are evaluated for subluxation, shallow acetabulum, femoral head/neck remodeling, acetabular rim/edge changes, and degenerative joint diseases. With the introduction of optical archiving and remote viewing from magnetic media the average report time is now 15 days with 87% of the evaluations finishing in less than 20 days.



= Normal:  Receive OFA Numbers


= Recommend repeat study in 6-8 months.


= Dysplastic

Normal hips on individuals 24 months or older are assigned a breed registry number and will periodically be reported to the parent club and AKC.
Abnormal findings are reported only to the


  1. DO YOUR HOMEWORK: Prospective buyers should check pedigrees for OFA numbers prior to purchasing a dog. If an OFA number cannot be verified assume the dog to be dysplastic until proven otherwise.
  2. PRELIMINARY EVALUATIONS: Can be performed as early as 4-5 months of age and OFA evaluations are about 90% accurate when compared to follow-ups at 24 months of age.
  3. ANESTHESIA: Is not required by the OFA but is recommended.
  4. HORMONAL EFFECT: Some female dogs show subluxation when radiographed around an estrus cycle which is not apparent when reradiographed in anestrus. The OFA recommends radiographing 3-4 weeks before or after a heat period or 34 weeks after weaning a litter of pups
  5. FILM COPIES: Due to optical archiving the OFA can no longer supply copies of films. If a copy is necessary ask your veterinarian to insert 2 films in the cassette prior to making the exposure. This will require about a 15% increase in the kVp to make an exact duplicate of the radiograph sent to OFA.



    = Breed Code (Pointer)


    = Ascending numerical order of normal individuals assigned a breed registry number


    = Phenotypic evaluation (Good)


    = Age in months when evaluation was done


    = Sex of individual (Male)


    = Tattooed

  7. REGISTRATION PAPERS: It is suggested a photocopy of the registry papers accompany radiographic submissions.

Correction of Anecdotal Misinformation

  1. There are no environmental factors which cause CHD.
  2. There is no evidence in the scientific literature that megadoses of vitamin C or any other supplement is beneficial in reducing the effects or preventing CHD.
  3. High caloric intake resulting in rapid growth and increase weight gain may exacerbate changes in dysplastic hips but will not create hip dysplasia.
  4. Exercise, running, jumping up and down, and slick floors will not cause hip dysplasia
  5. Prior injuries to the femurs and/or pelvis may be detected radiographically and are taken into account when evaluating hip status.

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