HD – Hip dysplasia

Hip Dysplasia in Maine Coon

Recent research shows that 37 % of all Maine Coons have Hip Dysplasia to some degree. All Maine Coon should always be HD X-rayed before breeding to check status and assess risk for the combination.


Principles – prinsipper

In order to decrease total risk for Maine Coons, and minimize serious cases of HD, these principles must be followed:

  1. Always HD x-ray before breeding
  2. Serious cases must be neutered, never mated
  3. “Some risk” cats only mate with normal, “HD free”
  4. Look at results for the whole family (siblings, parents etc) to evaluate total risk in the line

For å minske risiko i rasen som helhet, og begrense alvorlige tilfeller, må disse prinsippene følges:

  1. Alltid HD-røntge før avl
  2. Alvorlige tilfeller skal kastreres, aldri pares
  3. Katter med “noe risiko” skal kun pares med normale, trygge linjer
  4. Vurder resultatene for hele familiegruppen (kullsøsken, foreldre osv) for å få et bilde av total risiko i linjene

In severe form HD is a very painful and disabling disease. HD can also be mild, and a cat can often live well with this, but it should not be used for breeding. For cats that are not too heavily affected and with no patella luxation as additional condition, there are medical or surgical treatments available. Some cats are diagnosed with milder degrees of HD and show no clinical symptoms until they are older and develop ostoarthritis.

Alvorlig HD er en svært smertefull og hemmende lidelse. HD kan også være mild, slik at katten kan leve godt, men den bør da ikke brukes i avl. For katter som er alvorlig rammet, og som ikke i tillegg har kneproblemer (patellaluksasjon) så fins det medisinsk og kirurgisk behandling. Noen katter har svært mild HD og viser ingen kliniske symptomer før de blir eldre og har utviklet osteoartritt, forkalkninger.

Les også – Please also read:

Debunking some myths about HD – Myter om HD

The ideal age for HD X-rays – Ideell alder for HD-røntgen – (in Norwegian)


severe HD

Maine Coon with severe HD, grade 3-3 in PawPeds health programme.


How to test? – Hvordan teste?

The actual x-ray scan should be performed by an experienced veterinary who knows how to position correctly. The animal should ideally not be heavily sedated, only given a mild relaxant. Hip x-rays can be done from age 10 months (PawPeds) or 1 year (OFA) and up to 2 years age, always before mating for the first time. See comparison between the two systems below.

Hofterøntgen bør utføres av en erfaren veterinær som kan posisjonere korrekt, helst en som har gått gjennom NKKs kurs og er godkjent der. Katten bør ikke være tungt neddopet, men få mild sedasjon. HD-røntgen utføres før avl, fra 10 mnd (PawPeds) eller 1 års alder (OFA) og fram til 2 års alderen. Se sammenligning av de to systemene under.


This is how you do it:

  1. Download and fill in the form from PawPeds health programme, or OFA registry (or both)
  2. Pay for the evaluation: PawPeds 150 SEK pr cat, OFA 35/45 USD pr cat
  3. X-ray the cat at your veterinary, who will send the images in for evaluation together with the form
  4. Results within a few weeks
  5. If Normal or grade 1 (PawPeds) or Preliminary Excellent/Good (OFA), the cat can be mated, see below
  6. If Preliminary Fair, Borderline or Preliminary Mild (OFA), wait with matings until cat is 2 years old and do new x-rays

Slik gjør du:

  1. Last ned og fyll ut skjemaet, fra PawPeds helseprogram, eller OFA-registeret (eller begge)
  2. Betal avlesningen, PawPeds 150 SEK pr katt, OFA 35/45 USD (ca 350-450 NOK) pr katt
  3. HD-røntgen hos din  veterinær som sender inn røntgenbildene og skjemaet
  4. Resultatene kommer innen noen uker
  5. Dersom Normal eller grad 1 (PawPeds) eller Preliminary Excellent/Good (OFA) kan katten pares, se mer under
  6. Dersom Preliminary Fair, Borderline eller Preliminary Mild (OFA), vent med avl til katten er 2 år gammel, og ta nye røntgenbilder


PawPeds HD-form and info

OFA info and form


What we do at WesterosCat – Hva vi gjør

We follow the PawPeds health programme for HD

We x-ray all breeding animals through the programme, with public results then automatically added to the PawPeds database. All readings of x-rays is done by the same veterinary radiology expert Elisabeth Ball (from Feb 2020, 2014-2020 it was orthopedic specialist Dr Per Eksell and before 1 Oct 2014 Dr Lars Audell), to ensure the same scale of reading for all animals. He is also an expert on HD in cats, which is expressed differently than in dogs (Keller 1999, Perry 2016). PawPeds is a full health programme with total transparency, all results are public to the benefit of the breeder communities all over the world. Sometimes we also submit images to OFA for parallel evaluation and comparison.

We strongly recommend all Maine Coon breeders to x-ray their cats through PawPeds.

Vi følger PawPeds helseprogram for HD. Alle våre avlskatter blir røntget etter programmet, med offentlige resultater i PawPeds databasen. Alle avlesninger gjøres fra våren 2020 av veterinær Elisabeth Ball, for å sikre konsistente resultater på alle kattene. Iblant sendes røntgenbildene parallelt inn til OFA, for sammenligning.

HD-results for the WesterosCats

All test results can be found at each cat’s page.  See also complete and updated listHealth results for all our cats

Statistics – Statistikk

How common is HD in Maine Coon?

Summing up numbers from over 5000 x-rayed Maine Coons in PawPeds (Low 2019), and over 2700 in OFA (Loder 2017), it shows that:

  • 37 % of all Maine Coons have HD of some degree
  • approximately 10 % have moderate or severe HD and should not be used for breeding

What is known is that the risk of getting a cat with HD is much smaller if both parents have normal hips. This is no guarantee, but it betters the chances. HD is most probably recessive and polygenetic.

PawPeds put together this overview 25 Jan 2018, with a total of 3389 Maine Coon x-rayed between 2000-2018:

PawPeds statistics 2018

“gränsfall” = borderline

Debbie Sprenger at Macadamia Maine Coons in the Netherlands has also put together statistics and figures in her article “HD Analysis in the Maine Coon, part 1” (August 2020)


Sikre resultater for unge katter?

Studien til Corley (1997, se lenger ned under Research) viser at HD-røntgen av ung hund (12-24 mnd) gir evaluering som holder seg ved senere røntgen, i de fleste tilfeller: Normalhofter (Preliminary Excellent, Good) og dårlige hofter (Preliminary Moderate, Severe) vil vanligvis ikke få endret bedøming om de røntges på nytt ved høyere alder. Katters hofter er ferdigutviklede tidligere enn hos hund (Perry 2016), så resultatene bør være overførbare til katt. For ung katt som får resultat mellom disse (Preliminary Fair, Borderline, Mild), så er det lurt å ta ny røntgen ved 2 års alder. Det samme gjelder katter med grad 1 og grad 1-2 i PawPeds-systemet.

Reliable results for young cats?

The Corley study (1997, see below) shows that hip radiographs of young dogs (12-24 months old) in most cases give evaluations that are consistent also with later results. Healthy hips (Preliminary Excellent, Good) and bad hips (Preliminary Moderate, Severe) will normally not change if x-rayed again at a later age. Cats hips are fully formed at an earlier age than for dogs (Perry 2016) so this conclusion should be valid also for cats. For a young cat with hips evaluated with results between these (i.e. Preliminary Fair, Borderline, Mild) then new x-rays at 2 years age is strongly recommended. The same would apply for a cat with grade 1 and grade 1-2 in the PawPeds system.


PawPeds and OFA – differences

These two system have some important differences:

HD evaluation: PawPeds health programme OFA
Read by:  

1 veterinary radiologist: Elisabeth Ball (from 2020)

1 orthopedic specialist: Dr. G. G. Keller (12- 24 months age)

3 veterinary radiologists among 20-25 consultants (over 24 months age)

Number of readings: ca 300 HD evaluations for MCO pr year

over 5000 HD evaluations for MCO

ca 90 HD evaluations for MCO pr year

1242 HD public evaluations by 2018, 3215 HD evaluations total for MCO

Left-Right difference Yes Unilateral if 1 hip normal


Grade 1

Grade 2

Grade 3








Breeding recommendations  

Normal: Recommended

Grade 1: Mate with Normal only

Grade 2 and 3: Should not be used in breeding

Excellent and Good: Recommended

Fair: Mate with Excellent and Good

Preliminary Fair: Await new x-ray after 24 months age

Borderline, Mild, Moderate, Severe: Should not be used for breeding

Minimum age for final results* 10 months 24 months
Preliminary readings Yes, 6-10 months Yes, 12-24 months
Health programme Yes
signature before x-rays needed, and all results published to the benefit of all breeders

Only good results public

Published results Yes Normal only

Borderline and HD only by request

Price 150 SEK pr cat 45 USD pr animal

35 USD for preliminary reading before 24 months age

Pros Consistent reading by the same vet for all cats

All results public; full transparency

3 radiology specialists when cat/dog is over 24 months age
Cons One evaluation only Registry only, breeding recommendations developed for dogs

Bad results kept private

* See OFA recommendations for Preliminary results 12-24 months

PawPeds also used “Borderline” until around 2014. Breeding recommendations as for Grade 1.

Comparisons of actual results PawPeds and OFA

OFA started x-raying Maine Coon in 1990, and up until 2019 they have 3215 evaluations in their database, 1974 of these are hidden and not published online.

PawPeds started x-raying Maine Coon in 2000, and up until 2020 they have 5329 evaluations in their database.

PawPeds recommend never breeding grade 2 and grade 3, which means 16,1 % of Maine Coon should not be used for breeding. The total for grade 1, 2 and 3 (dysplastic hips) is over 37 %.

OFA has more vague recommendations, but normally advices to not use dysplastic hips; Mild, Moderate and Severe. That is over 25 % of Maine Coons. If only Moderate and Severe are taken out of breeding, this means ab 8,4 % should not be used for breeding. Also note that Preliminary Fair and Preliminary Mild should always be x-rayed again after the cat is over 24 months old, for a final result.


Descriptions from the OFA website:


Research and Resources – Learn more

List of references for the website also here

Research on HD in cats

There are few scientific papers on HD in cats compared to HD in dog breeds. However,  a large study was published autumn 2019 to describe prevalence and hereditability, based on PawPeds data and including over 5000 Maine Coons. Also two papers from 1999 point at some important issues, and two recent articles from 2016 describes cat HD.


Low et al. 2019. “Demography, heritability and genetic correlation of feline hip dysplasia and response to selection in a health screening programme.” Nature Scientific Report. Direct link.

“Feline hip dysplasia (FHD) is a debilitating condition affecting the hip joints of millions of domestic cats worldwide. Despite this, little is known about FHD except that it is relatively common in the large breed Maine Coon. We used 20 years of data from 5038 pedigree-registered Maine Coon cats in a radiographic health screening programme for FHD to determine, for the first time, its heritability, genetic correlation to body mass and response to selection. FHD prevalence was 37.4%, with no sex predilection; however, FHD severity increased with age and body mass. Heritability of the radiographic categories used to classify FHD severity was 0.36 (95%CI: 0.30–0.43). The severity of FHD symptoms was also genetically correlated with body mass (0.285), suggesting that selection for a large body type in this breed concurrently selects for FHD. Support for this was found by following generational responses to selective breeding against FHD. Not only did selective breeding successfully reduce the severity of FHD symptoms in descendants, but these cats were also smaller than their ancestors (−33g per generation). This study highlights the value of breeding programmes against FHD and cautions against breed standards that actively encourage large bodied cats.”


Smith G. K. 1999. “Evaluation of the association between medial patellar luxation and hip dysplasia in cats.” In: Journal of American Veterinary Medicine. 1999 Jul 1;215(1):40-5.

Clinically normal cats may have a certain degree of laxity in the stifle joint, evident as medial patellar subluxation (< grade 1). There is a weak association between MPL and HD, and both conditions may develop, alone or in combination, more frequently than has been reported.


Keller G. G. 1999. Hip dysplasia: a feline population study. In: Veterinary radiology & ultrasound. 1999 Sep-Oct;40(5):460-4.

This study of 684 cats of 12 breeds conclude that “the radiographic appearance of hip dysplasia in cats is different than in dogs. A shallow acetabulum with remodeling and proliferation involving the cranio-dorsal acetabular margin were the most common radiographic signs. Minimal remodeling of the femoral neck was seen.”


Perry, Karen L. 2016. “The Feline Hip. How is it different from the canine?

This article describes how cat hip dysplasia is very different from HD in dogs.

  1. In cats it is present at birth (like for humans) whereas for dogs it develops during day 30-60 in predisposed puppies.
  2. In cats the shallow acetabulum is the main problem, not the subluxation of the femoral head (like in dogs)

Perry, Karen. 2016. “Feline Hip Dysplasia: A Challenge to Recognise and Treat

The reported incidence of hip dysplasia (HD) in cats varies dramatically between studies, but the condition is likely more common than we realise. There is little doubt that cats with HD and associated osteoarthritis (OA) suffer pain, and this warrants appropriate therapy.

Clinical signs of HD in cats are often gradual in onset, making them difficult to appreciate, but may include inactivity, pelvic limb lameness, difficulty jumping and climbing stairs, and reluctance to squat to defecate. Often lameness is bilateral, and can be particularly difficult to recognise. The most common radiographic finding is an abnormally shallow acetabulum. Subluxation, however, is not consistently associated with OA in cats and therefore the role that joint laxity plays in disease progression remains uncertain. Degenerative changes of the femoral head and neck seem to develop later than in the dog, and are less marked.

The majority of cats respond to non-surgical management with environmental modulation, physical therapy, dietary modulation, weight loss, nutraceuticals and drug therapy. Should non-surgical management not provide sufficient relief, two salvage surgical options are available: femoral head and neck excision (FHNE) and total hip replacement (THR). While there is a risk of complications with micro-THR, the positive outcomes that have been reported indicate that it should be considered in the treatment of coxofemoral pathology in cats in the same way that THR is considered for larger dogs, especially given the inconsistent results associated with FHNE. Monitoring the effect of treatment is challenging as the assessment of pain in cats is complex and there is no validated scoring system or owner-completed questionnaire yet available for cats.

There is a paucity of clinical reports focusing solely on HD in cats. The author draws on a combination of published studies, in cats, dogs and humans, as well as personal clinical experience.


Research revealing statistics

Loder, Randall et al. 2017. “Demographics of hip dysplasia in the Maine Coon cat“.  In: Journal of Feline Medicine & Surgery, April 2017 DOI: 10.1177/1098612X17705554

Methods: The complete hip dysplasia registry (public and private) collected by the Orthopedic Foundation for Animals through April 2015 was accessed. There were 2732 unique cats; 2708 (99.1%) were Maine Coons, and only these were studied. Variables analyzed were sex, month/season of birth and hip dysplasia score. Two groups were created: those with and without FHD. P <0.05 was considered statistically significant.

Conclusions and relevance: This is the largest demographic study of FHD in the Maine Coon cat. The overall prevalence in the Orthopedic Foundation for Animals registry was 24.9%, and slightly higher in males (27.3%) than females (23.3%). Dysplasia was more severe in bilateral than unilateral cases and with increasing age. Caution should be used when extrapolating these findings to other feline breeds or other groups of Maine Coon cats. Further studies need to be performed among other breeds and geographic locations to better understand the demographics of feline hip dysplasia.”

2708 Maine Coons screened for HD showed that 24,9 % had hip dysplasia.



Other research

Corley, EA, et al. 1997. “Reliability of Early Radiographic Evaluation for Canine Hip Dysplasia Obtained from the Standard Ventrodorsal Radiographic Projection.” JAVMA. Vol 211, No. 9, November 1997.

This study of dogs shows that early age for HD screening is reliable, and we can assume that numbers for cats are similar.

Researchers found a “100% reliability for a preliminary grade of excellent being normal at 2 years of age (excellent, good, or fair). There was 97.9% reliability for a preliminary grade of good being normal at 2 years of age, and 76.9% reliability for a preliminary grade of fair being normal at 2 years of age. … For normal hip conformations, the reliability was 89.6% at 3-6 months, 93.8% at 7-12 months, and 95.2% at 13-18 months. These results suggest that preliminary evaluations of hip joint status in dogs are generally reliable. However, dogs that receive a preliminary evaluation of fair or mild hip joint conformation should be reevaluated at an older age (24 months).


Lascelles et al. 2012. “Relationship of orthopedic examination, goniometric measurements, and radiographic signs of degenerative joint disease in cats.” In: BMC Veterinary Research 2012, 8:10

This study shows that a clinical examiniation is not enough to discover which cats has joint problems – Degenerative joint disease (DJD).

“Joints with DJD tended to have a decreased range of motion. The presence of pain increased the odds of having DJD in the elbow (right: 5.5; left: 4.5); the presence of pain in the lower back increased the odds of spinal DJD being present (2.97 for lumbar; 4.67 for lumbo-sacral).

Conclusions:  Radiographic DJD cannot be diagnosed with certainty using palpation or goniometry. However, negative findings tend to predict radiographically normal joints. Palpation and goniometry may be used as a tool to help to screen cats, mostly to rule out DJD.”


Indrebø, Astrid 2013. HD-index (in Norwegian)

Astrid Indrebø er rådgivende veterinær for NKK. Hun skriver om viktigheten av et bredt bilde: En hund med HD men der foreldre og kullsøsken alle har normalhofter er et bedre avlsdyr enn en hund med normalhofter, der HD fins hos foreldre og søsken. Jo flere individer som er HD-røntget, desto bedre og sikrere avgjørelse kan tas.


Further info

Beuchat, Carol. 2019. Blogpost on HD research in dogs, and updates. Institute of Canine Biology.


Breeds at risk

These breeds are recommended to x-ray hips before breeding:

By FIFe Health and Welfare Commission: PER/EXO, MCO, NFO, ABY/SOM, BEN, DRX

Also known risk: SIB, BRI (BSH, BLH), SRL/SRS

Breeds with HD results in the PawPeds database 2013



PawPeds HD Health programme

Cornell University College of Veterinary Medicine about Hip Dysplasia

OFA Breeding Recommendations  and OFA Ratings explained

Winn Feline about Hip Dysplasia (PDF)

Dr Karen Perry, Michigan State University on Feline Hip Dysplasia


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