Hip Dysplasia (HD) is considered to be the most common heritable orthopaedic disease of dogs, affecting to variable degrees virtually every breed. HD results in a significantly higher risk of the dog developing Degenerative Joint Disease (DJD). It is this DJD that then causes pain, loss of mobility and quality of life.
Many breeders, vets and organisations have shown a commitment to eliminating HD by adhering to 
the current Hip Dysplasia Schemes run by the New Zealand Veterinary Association and the Australian Veterinary Association. These schemes score hip radiographs to identify individual dogs with "good" hips that can then be used as breeding stock.
While these schemes have successfully reduced the severity of HD, an ideal scheme would result in faster reduction in the incidence of HD.
PennHIP (www.pennhip.org) uses a different method to assess for HD and the potential of a dog to develop DJD. This radiographic technique measures the actual laxity of hip joints by radiographing the joints while they are distracted. The films are then sent to the United States for assessment. Loose hips have a high risk of DJD, while tight hips have a low risk of DJD.
PennHIP has been extensively researched and has been shown to have a higher heritability than the standard HD assessment schemes. This means selection based on PennHIP will result in more rapid progress in reducing the incidence and severity of HD.
PennHIP scores are highly repeatable at different ages. PennHIP Scores have an 80% repeatability between 4 months and one year of age and 93% between one year and 2 years of age. This means that potential breeding stock can be screened for HD from 4 months of age.
Veterinarians must be specially trained and pass examinations in order to use the PennHip method of assessing hips. Dr Nigel Kittow attended a training course last year in Sydney and has received accreditation to perform these radiographs.
Radiographic equipment and techniques must be of a very high standard to accurately assess dogs for HD. This is especially important in the large breeds which are technically more difficult. To enable us to achieve the highest quality radiographs possible we have recently purchased a new high output Radiography Unit.
The new machine has optimised the quality of our hip radiographs in large dogs.
The established scheme will continue to play the major role in HD management for the near future in NZ. PennHIP however has a signifcant role to play for breeders who are really serious about minimising HD in their lines.
In summary
• We can screen dogs from 4 months of age.
• This allows
1. Better management of at risk dogs
2. Selection of preferred breeding stock at an early age.
• Rescreen to confirm breeding dogs at 1-2 years of age.
• The lower the score, the faster and greater will be the genetic gain in your breeding lines.
We are very excited about the future of PennHIP. The Australian Veterinary Association has recently accepted it in parallel to its conventional scheme. We believe the future lies in this direction.
If you are serious about reducing the incidence of HD in your breed, or knowing the risk of an individual dog developing HD arthritis, we urge you to visit www.pennhip.org for more scientific information.
If you would like to discuss HD management, please do not hesitate to contact us.
Hip Dysplasia is generally considered a disease of dogs. However it is also a significant problem in some cat breeds, especially the Maine Coon. While there is copious research in dogs, little research has been done in cats to assess the best method of screening for this disease. In dogs there is a clear link between joint laxity and Hip Dysplasia. A study by Langenbach et al. established a link between joint laxity and DJD in cats, although the relationship seems different to that in dogs.
At MVS we have recently begun screening cats for Hip Dysplasia using the PennHIP methodology. The information from this testing gives breeders helpful information when selecting cats for breeding.
If you are interested in learning more about PennHIP visit www.pennhip.org or contact MVS.