HD – Hip dysplasia

Hip Dysplasia in Maine Coon

Around 25 – 30 % 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.

Debunking some myths about HD (in Norwegian)

HD can be mild, and a cat can often live well with this, but it should not be used for breeding. In severe form HD is a very painful and disabling disease. For cats that are not too heavily affected and with no patella luxation as additional condition, there are medical or surgical treatments available.

What we do at WesterosCat

We follow the Health programme for HD started by the breed society Maine Coon-katten, now organized by PawPeds. We x-ray all breeding animals through the programme, and results are then automatically added to the PawPeds database. All interpretation of x-rays within the programme is done by the same veterinary expert Dr Per Eksell (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). We have tested out also sending the same images to OFA for comparison, in addition to PawPeds. However the OFA registry and recommendations are designed for dogs, and is less suited for cats. PawPeds is in addition a full health programme with total transparency, all results are public to the benefit of the breeder communities all over the world.

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

It is clear that x-rays and reading of the images by an expert veterinary is needed for a correct diagnosis. Some animals are diagnosed with milder degrees of HD, but show no clinical symptoms, at least not until they are older and develop ostoarthritis.

severe HD

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

How to test?

The actual x-ray scan should be performed by an experienced veterinary, and the animal should not be heavily sedated, only given a mild relaxant. A heavily sedated animal may be evaluated as being affected, even if it is not, or as having severe HD instead of mild or borderline status. A young animal might sometimes show  “joint laxity” and look as if it has symptoms, while a later scan shows healthy hips. As cats grow older, osteoarthritis will develop. Ideally the hip x-rays should be done between ages 10 months and 2 years old.

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


How common is HD in Maine Coon?

Summing up numbers from over 3000 x-rayed Maine Coons in PawPeds, and over 2700 in OFA (Loder 2017), it shows that:

  • 25-30 % of all Maine Coons have HD of some degree
  • approximately 7-10 % 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:

“gränsfall” = borderline


HD evaluation: PawPeds health programme OFA
Read by:  

1 orthopedic specialist: Per Eksell

Before 24 months age: 1 veterinary, OFA employee

From 24 months and older: 3 veterinary radiologists among 20-25consultants

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 only

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

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

Minimum age for valid 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 $ 35 pr animal

$ 30 for preliminary reading before 24 months age

Pros Consistent reading by the same vet for all cats

Orthopedic specialist in cat HD

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

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

OFA scale compared to the A-E system used by the FCI, and other Kennel club scales.


Research and Resources – Read more

List of references for the website here

Research on HD in cats

There are few scientific papers on HD in cats compared to HD in dog breeds. However, two papers from 1999 point at some important issues, and a recent article describes cat HD:

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)



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

Objectives: The aim of this study was to study the demographics of feline hip dysplasia (FHD) in the Maine Coon cat.

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.

Results: The youngest cat with FHD was 4 months of age. The majority of the radiographs (2604/2708 [96.2%]) were performed between 4 and 60 months of age. Non-borderline scores for these 2604 cats were available in 2548, and were the data used for this study. The overall prevalence of FHD was 24.9% (635/2548), and was slightly higher in males (279/1023 [27.3%]) than females (356/1525 [23.3%]) ( P = 0.025). Those with more severe dysplasia were older. The percentage of bilateral FHD was 56%, and bilateral cases had more severe dysplasia than unilateral cases but with no age difference. Month/season of birth or geographic region of origin did not influence the prevalence of FHD.

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  http://www.biomedcentral.com/1746-6148/8/10

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

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


Cornell University College of Veterinary Medicine about Hip Dysplasia

OFA Breeding Recommendations  and OFA Ratings explained

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