Hip Health in Standard Poodles: Why We Use Both PennHIP and OFA

Our Program's Hip Results

What Is Hip Dysplasia?

Hip dysplasia is a developmental condition in which the ball (femoral head) and socket (acetabulum) of the hip joint don't fit together properly. Instead of moving smoothly and securely, the joint experiences abnormal motion and contact stress with every step. Over time, this leads to cartilage wear, bone remodeling, inflammation, and osteoarthritis.

The condition is heritable — a dog with poor hip conformation or excessive joint laxity is significantly more likely to produce offspring with the same problems. Heritability estimates in dogs range from 25% to over 50% depending on the breed, which means strategic selection pressure from breeders can — and does — move the needle.

Importantly, hip dysplasia is not always obvious to look at or feel. Many dogs with radiographically poor hips appear physically normal and show no obvious lameness until arthritis has progressed significantly. This is why radiographic and laxity-based testing is essential — you cannot screen hips with your eyes.

Hip Conformation — What OFA Measures

Conformation refers to the structural shape and fit of the hip joint at skeletal maturity. In simple terms: does the ball fit well in the socket? Is the socket deep enough?

The OFA method evaluates hip conformation via a standard ventrodorsal extended-leg radiograph taken at a minimum of 24 months of age. Three independent radiologists evaluate the image and reach a consensus grade:

• Passing grades: Excellent / Good / Fair
• Non-passing: Borderline / Mild Dysplasia / Moderate Dysplasia / Severe Dysplasia

OFA has been the industry standard since 1966 and has accumulated a massive database of breed-specific results. It is excellent at identifying structural abnormalities — malformed sockets, subluxated femoral heads, flattening of the joint surface, and early degenerative changes.

The limitation: The extended-leg positioning used for OFA actually tightens the hip capsule and compresses the joint, which can make a mildly lax hip appear structurally normal. A dog can pass OFA and still have underlying joint laxity that predicts future arthritic change.

Hip Laxity — What PennHIP Measures

Laxity refers to how loose the hip joint is — specifically, how far the femoral head can be passively displaced from the socket when force is applied. This passive laxity is distinct from how the joint looks structurally. A hip can look well-formed on an extended radiograph but still be excessively loose.

PennHIP (University of Pennsylvania Hip Improvement Program) was developed in the early 1990s by Dr. Gail Smith and colleagues at Penn's School of Veterinary Medicine. It uses a distraction technique: a specially designed positioning device applies lateral force to the hip joints, displacing the femoral head outward, and the degree of displacement is measured from the resulting radiograph.

The result is a Distraction Index (DI) for each hip:

• Scale: 0.0 to 1.0
• Lower = tighter = less laxity = less risk
• Higher = looser = greater laxity = greater OA risk

Research by Smith et al. demonstrated that DI is a strong predictor of future osteoarthritis — dogs with higher DI values are significantly more likely to develop hip OA over their lifetimes, regardless of their OFA grade.

Key advantages over OFA:

• Can be performed as early as 16 weeks (vs. OFA's 24-month minimum)
• Objective, quantitative measurement vs. subjective radiographic grading
• Detects laxity that the OFA extended position can mask
• Proven superior to OFA as a predictor of osteoarthritis risk
• Enables trend tracking across breeding generations

Why Both Tests Together: The Research

Using OFA alone for breeding selection doesn't move the needle on hip health. Using both OFA and PennHIP does. This isn't a theoretical claim — it has been demonstrated in published clinical research.

When you add laxity-based selection pressure to structural selection, you're targeting both dimensions of hip health simultaneously — and you get faster, more meaningful improvement in each successive generation.

What This Looks Like in Our Program

We require both evaluations on all breeding dogs. Our minimum standards are:

• OFA: Excellent, Good, or Fair
• PennHIP DI: At or below the breed median (0.46 for Standard Poodles), with preference for dogs in the tightest 25–30%

We track DI scores across litters with the goal of trending tighter hips with each generation. When both parents have DI values well below the breed median — like Fonzie at 0.24 — their offspring start with a meaningful genetic advantage.

All of our dogs' OFA certifications are publicly verifiable at ofa.org using their registered name or microchip number.

A Note on "Passing" OFA and Hidden Laxity

A dog can have a Fair — or even a Good — OFA rating and still carry enough hip laxity to be at meaningful risk for arthritic change and to transmit that laxity to offspring.

This is not a criticism of OFA — it is an excellent tool for what it measures. But it was never designed to measure passive laxity, and using it as the sole selection criterion leaves a dimension of hip health completely unaddressed. PennHIP fills that gap directly.

Both tests together tell you what neither test can tell you alone.