How Elbow Scores Work: A Comparison of Grading Systems

The International Elbow Working Group published standardized grading guidelines in 1990 with the explicit goal of enabling cross-border comparison of screening results. Thirty-four years later, we are no closer to that goal. The OFA uses its own modified scale, the BVA/KC employs yet another system, and individual national kennel clubs interpret the IEWG guidelines with sufficient variation that comparing a German "ED 0" to a Swedish "UA 0" requires careful consideration of methodology differences. This fragmentation frustrates breeders attempting international pedigree analysis and impedes meta-analysis of prevalence data.

The IEWG Standard: Foundation and Framework

The International Elbow Working Group, founded in 1989 by veterinary radiologists from 14 countries, established the baseline grading protocol still referenced by most national schemes. The original IEWG grades assessed both primary lesions (FCP, OCD, UAP) and secondary osteoarthritis, assigning a 0-3 score based on severity.

Grade 0

Normal elbow, no evidence of incongruity, sclerosis, or arthrosis

Grade 1

Mild arthrosis, osteophytes <2mm, slight sclerosis of trochlear notch

Grade 2

Moderate arthrosis, osteophytes 2-5mm, obvious sclerosis, possible primary lesion

Grade 3

Severe arthrosis, osteophytes >5mm, clear primary lesion (FCP/OCD/UAP)

The IEWG protocol requires minimum age of 12 months, extended lateral and cranio-caudal radiographic projections, and evaluation by a certified screener. However, the 2001 revision introduced problematic ambiguity by allowing national organizations to set their own certification standards for screeners and to modify positioning requirements. Lang et al. (2007) documented significant inter-observer variability even among IEWG-certified evaluators, with agreement rates of only 72% for Grade 1 versus Grade 0 classifications.

OFA Elbow Certification: The American Approach

The Orthopedic Foundation for Animals developed its elbow certification program in 1990, deliberately simplifying the IEWG scale while adding categories for inconclusive results. The OFA system grades each elbow independently and reports the worse of the two scores as the official result.

The OFA maintains a searchable public database at ofa.org, which constitutes the largest repository of elbow screening data worldwide with over 750,000 evaluations. However, the OFA's voluntary submission policy creates significant selection bias: Keller et al. (2011) estimated that owners submit results for dogs grading Normal at 3-4 times the rate of affected dogs, artificially depressing reported prevalence.

BVA/KC Elbow Scheme: The British Protocol

The British Veterinary Association and Kennel Club jointly administer the UK elbow screening scheme, which diverges from both IEWG and OFA approaches. Rather than a single grade, the BVA/KC system scores each elbow on a 0-3 scale and reports both scores, with the sum used for breeding recommendations.

The BVA/KC scheme requires three radiographic views (neutral lateral, flexed lateral, and cranio-caudal), exceeding IEWG minimum requirements. All radiographs are submitted to a centralized panel of BVA-appointed scrutineers, providing more consistency than schemes allowing local veterinary evaluation. However, the resulting bottleneck means UK breeders typically wait 4-6 weeks for results.

International Inconsistencies: A Persistent Problem

The fundamental challenge for breeders working across borders is that equivalent radiographic findings may receive different grades depending on which system evaluates them. Fluckiger et al. (2006) submitted identical radiograph sets to evaluators in six countries and found Grade 1 versus Grade 0 disagreement in 31% of cases.

Which System Is Most Reliable?

Reliability studies consistently show the OFA three-evaluator consensus approach produces the highest inter-observer agreement (85-90%), followed by BVA/KC panel review (80-85%), with single-evaluator IEWG systems showing the greatest variability (70-80%). However, the OFA's 24-month minimum age requirement means some dogs with early-onset disease are missed if only screened once at 12 months under IEWG protocols.

For breeding programs, I recommend the following hierarchy when interpreting historical screening data:

1. OFA Normal (24+ months) - Highest confidence, though submission bias inflates apparent clearance rates
2. BVA/KC 0:0 - Rigorous evaluation, individual elbow data valuable for pedigree analysis
3. IEWG Grade 0 (FCI member) - Acceptable if evaluator certification confirmed
4. National scheme "clear" - Verify protocol details before relying on result

Certification Number Examples by Country

Understanding certification formats helps verify authenticity when reviewing breeding documentation:

The Case for Harmonization

The veterinary orthopedic community has debated grading standardization for decades without resolution. The IEWG's 2018 position statement acknowledged ongoing inconsistencies but stopped short of mandating enforcement mechanisms. Meanwhile, genomic approaches to ED selection are emerging that may eventually supersede radiographic screening entirely.

Until genomic tools mature, breeders must navigate the current patchwork of systems. My practical recommendation is to establish relationships with screening veterinarians who maintain consistent positioning protocols and submit all breeding stock to the same evaluators when possible. Temporal consistency within a breeding program matters more than precise alignment with any particular international standard.