Why PennHIP for Dogs Is the Gold Standard for Hip Scoring
If you’ve spent any time in the world of dog breeding — whether you’re producing working dogs, show dogs, or beloved family companions — you’ll know that hip dysplasia is one of the most frustrating and heartbreaking conditions a dog can develop.
It’s painful, costly to manage, and often only becomes apparent after a dog has already been bred. The good news is that we have better tools than ever to tackle it head on. One of the most powerful — and most underused in the UK — is PennHIP.
What Is PennHIP for Dogs?
PennHIP — short for the Pennsylvania Hip Improvement Program — was developed in the early 1990s at the University of Pennsylvania School of Veterinary Medicine, and is now operated by Antech Imaging Services.
It evaluates hip joint laxity, or looseness, using three radiographic views taken under sedation or general anaesthesia. These produce a precise numerical Distraction Index, known as DI, for each hip.
A lower DI means a tighter, better-conformed joint. A DI of 0.3 means the femoral head moves 30% of its radius away from the socket under distraction — no interpretation, no subjectivity, just a number.
The Three Views – What They Show
Hip-Extended View
The standard BVA/KC view. The extended position tightens the joint capsule, presenting hips to best advantage — and masking underlying laxity.
Compression View
Femoral heads pressed firmly into the acetabula. This establishes baseline joint congruity — how well the ball fits the socket at its best.
Distraction View
Passive laxity revealed. The femoral heads subluxate laterally away from the acetabula — the key measurement that the extended view conceals.
The critical difference: Compare the compression and distraction views side by side. The degree of subluxation visible in the distraction image is the Distraction Index made visible — passive hip laxity that would be entirely concealed in the hip-extended position used by conventional scoring. Dogs that appear normal on a standard radiograph may harbour significant laxity when properly evaluated.
The Problem With Conventional Dog Hip Scoring
In the UK, the most widely used hip screening system is the BVA/KC Hip Dysplasia Scheme. Dogs are scored on nine anatomical features of each hip, producing a total score from 0 to 106. It is a familiar system, and widely recognised by breed clubs — but its fundamental limitation is what it actually measures.
The conventional hip-extended view on which BVA/KC scoring is based is a static assessment of secondary changes. It looks for evidence of damage that has already occurred.
Crucially, research has demonstrated that this position actively masks hip laxity rather than revealing it. Hip laxity is maximal with the hind legs in the weight-bearing position used by PennHIP, and is concealed in the hip-extended position.
The result is that dogs assessed as normal under static scoring methods have been shown to harbour significant passive hip laxity when properly evaluated. These so-called “false normals” can remain in breeding populations and silently perpetuate the problem.
Why Progress Can Be Slow With Conventional Scoring
There are two reasons why conventional hip scoring has produced only slow improvements in breed populations.
First, the hip-extended view is a poor predictor of which dogs will actually go on to develop osteoarthritis.
Second, because the hip-extended score reflects only a weak signal of the underlying genetic picture, selective breeding based on it produces limited genetic progress — even when breeders apply it conscientiously over many generations.
PennHIP addresses both problems. The Distraction Index is a much stronger predictor of osteoarthritis and, because it measures the underlying laxity more accurately, selection pressure applied using DI scores translates into real, measurable genetic improvement across generations.
The Benefits of PennHIP for Dog Breeders
For dog breeders, PennHIP provides earlier, more objective and more actionable information than conventional hip scoring alone.
Earlier, Actionable Information
PennHIP can be performed reliably from just 16 weeks of age. A dog’s DI at 16 weeks is highly predictive of its adult score.
This means selection decisions can be made before a dog has been bred, before significant investment has been made in a working dog’s training, and while there is still time to act meaningfully within a litter — rather than waiting until a dog is one or two years old.
Objective, Repeatable Measurement
The DI is a precise number, not a subjective grade. Two certified PennHIP practitioners examining the same dog should reach the same result, regardless of who performs the procedure or where.
This consistency is essential for breeders thinking across multiple generations.
Population-Based Breed Comparisons
Results are expressed as a percentile within the breed, drawn from a large international database.
You’re not just assessing one dog in isolation — you’re understanding exactly where it sits relative to the broader breed population, and selecting with genuine precision.
Proven Generational Improvement
Only by directly applying selection pressure to reduce the Distraction Index has marked, sustained reduction in hip joint laxity been demonstrated across generations.
PennHIP gives breeders both the tool and the ongoing data to prove their programme is working.
Recognised and Respected
PennHIP is recognised by the American Kennel Club through its Canine Health Information Center, and interest in its use as a primary hip screening tool continues to grow internationally.
For breeders producing dogs for export, or working with organisations that prioritise evidence-based health screening, PennHIP results carry real weight.
Why Are There So Few Certified PennHIP Practitioners in the UK?
In the United States, veterinarians are permitted to remain in the room and manually assist with patient positioning during X-ray exposure. In the UK and across Europe, radiation protection legislation does not permit this — positioning must be achieved and held without manual support during the exposure itself. This makes PennHIP genuinely demanding to perform correctly and consistently.
Certification requires completing a structured training programme and submitting radiographs on multiple patients for independent quality assessment. The small number of certified practitioners in the UK reflects that challenge — not a lack of accessibility once you have found someone qualified to perform it.
A Note on Individual Management vs Breeding Decisions
Weight management and appropriate exercise can influence how severely hip dysplasia affects an individual dog during its lifetime — genuinely valuable for that animal’s welfare. But they have no bearing on the genetic contribution that dog passes to its offspring. Managing the phenotype of one generation does nothing to improve the genetics of the next. Only informed, laxity-based breeding selection does that.
Final Thoughts
Hip dysplasia remains one of the most prevalent and welfare-significant orthopaedic conditions in dogs. We have known for decades that it has a strong heritable component.
We now have a validated, precise, early-screening tool that demonstrably reduces its incidence when applied consistently — and the evidence base behind it is stronger than any other hip evaluation method currently available.
The question for breeders is a simple one: if a better tool exists, why wouldn’t you use it?
We can help
Dr Alan Shackleton at Potton Vets is one of a small number of individually PennHIP-accredited veterinary surgeons in the UK. PennHIP evaluation is available now — get in touch to find out more or to book an appointment.
Whether you are a hobby breeder, a working dog breeder, or a breed club member looking to raise the bar on health screening within your programme, we would love to hear from you.
Contact us with any questions and to book:
Phone: 01767 260007 | Email: clients@pottonvets.co.uk
