Q: "I have sent you a copy of the e-mail i sent [NAME OMITTED], bcause [NAME OMITTED], told me that hip dysplasia is not a problem in America... i du not agree that ferrets don't have the weight/muscle/bone growth imbalance like large dogs. Do you agree with [NAME OMITTED]? Hip dysplasia is a problem in ferrets in Denmark, but they do not show any pain what so ever, and i think that is why the problem does not exist in America, because no x-rays have been taken." A: First, I am not a veterinarian; I am a zooarchaeologist intensively trained in comparative osteology (among other things). Most of the vets on this list know far more about hip dysplasia than I do. I hope they will speak up and correct any mistakes I might make in this response. Hip dysplasia (HD) is a progressive, degenerative joint condition found in large breeds of dogs, although it is not unheard of in smaller canines and other animals. The Hip Dysplasia Registry of the Orthopedic Foundation for Animals (OFA) at the University of Missouri, Columbia sets standards for hip dysplasia in dogs, and reviews and grades hip dysplasia in canines and other animals. Researchers at the University of Pennsylvania (PennHip) are also looking at the condition, as well as numerous veterinarians and animal scientists. Hip dysplasia has been noted in Maine Coon cats, but is not limited to that variety. Dysplasia has been reported in pigs, sheep, other domestic animals, and even in humans. According to Dr. Greg Keller of the OFA, hip dysplasia has NOT been reported in ferrets (at least to the OFA), and he does not know of any peer-reviewed literature that suggests the condition has ever been reported. My own extensive and protracted search has found none. I am not going to discuss the causes of hip dysplasia; how could I explain in a few paragraphs a disease that in 1996 one of the top researchers, Dr. James A. Baker, called "baffling?" Thought to be heritable, caused by multiple genes at multiple locations (polygenic), hip dysplasia is not limited to hips, but can effect all joints, especially those of the shoulder, knee and between the vertebrae. Regardless of the obvious genetic influence, there is a strong environmental aspect controlling gene expression--hip dysplasia can be controlled or prevented by reducing growth during development by limiting food intake. From my point of view (as a zooarchaeologist), it is extremely difficult to identify pathological cause in prepared skeletons. Veterinarians have the advantage in that they can inspect X-rays taken from living individuals, and physically inspect affected individuals for pain, mobility, range of motion, and other symptoms. All I can do is note the presence of osteoarthritis on individual bones and realize some sort of degenerative changes have taken place, but without usually being able to say WHAT caused the problem. That is to say, I can easily note the presence of arthritic changes, but I usually can't say what caused them. However, in cases of animals having hip dysplasia, I CAN identify the cause in maybe 70% of the cases (based on blind tests), based on a number of criteria: no obvious presence of injury or infection, presence of osteoarthritis in shoulder, knee, and intervertebral joints, and specific changes to the femoral-acetabular structures. I have found these changes in the skeletons of large dogs, a few smaller ones, sheep, and a few cats, but as of yet, I have never seen them in a ferret, and I have inspected hundreds of ferret skeletons. That is not to say I haven't found arthritic changes in ferret hips; they are common enough in older ferrets for me to consider their presence as a typical condition. However, in the example of dysplasia I have inspected, the walls and floor of the acetabulum are eroded, and the neck and head of the femur are significantly changed. The only time I have seen those changes in ferret skeletons have been because of injury or infection; not because of a heritable condition. I have a few thoughts on the issue. While dysplasia is found in most breeds of dogs, it tends to affect the larger breeds most often. The same is true with dysplasia in cats. These animals have been selectively bred to be significantly larger than their progenitors (gray wolf and wildcat). Ferrets have, to date, been spared the human desire to manipulate size. Second, ferrets, as with other small mustelids, have "loose joints"; that is, ferret limbs are designed to twist and turn in ways impossible for cats or dogs (or at least quite painful). This is because ferrets evolved chasing animals down burrows and follows other adaptations allowing hunting in small, narrow spaces, such as a unified internal carotid, small external ears, powerful neck, and extremely supple vertebral column. Because of this, there are subtle differences in how the femur is attached in the hip when compared to dogs or cats. For example, the acetabulum is shallower, which allows the femur greater range of motion; this "looseness" allows the legs great flexibility when wiggling down burrows. The neck of the femur is also comparatively longer in ferrets, aiding extension of motion. These differences MAY preclude the types of problems seen in the joints of large cats and dogs. Third, the problems found in cats and dogs can be largely eliminated by slowing growth by limiting diet in developing individuals. Ferret size is ALREADY limited by diet and neutering, so the rapid growth that imbalances the weight/muscle/bone ratios in dogs and other domesticated animals is not typically seen in ferrets. Therefore, I strongly agree with your original respondent that hip dysplasia is not a problem in American ferrets. As for the lack of observation of dysplasia in American ferrets being due to a lack of X-rays: I disagree. X-raying ferrets is common in veterinary care because it is a relatively rapid and cheap method to check for obstructions, masses, organ enlargement, and bone problems. While vets may not be primarily looking for signs of hip dysplasia, they WOULD notice the changes in the joints associated with the disease. Maybe not every vet, but enough would notice so that a warning would be mentioned in ferret health literature. Remember, osteoarthritis is PAINFUL; even without significant osteological changes, animals suffering from hip dysplasia are in obvious pain from movement or physical manipulation. If, as you mention, ferrets are not in pain, it is doubtful they are actually suffering from dysplasia. I wonder if the laxness in the ferret hip joint--normal compared to dogs or cats--is confusing the issue. Personally, while I think ferrets COULD potentially suffer from dysplasia of the hip (or other joints), they just haven't been subjected to the same type of selective breeding for size as in cats or dogs (or other domestic animals). From an outsider's perspective, it seems that breeding for size triggers the problem. However, as an owner of EXTREMELY large ferrets, I worry about the current trend of some ferret owners trying to breed ferrets much larger than typically found. It may be that if the trend continues, ferrets will suffer dysplasia as genetic defects are increased with inbreeding for size. However, I have some good news. If ANYONE on this list (or reading this post) suspects a ferret has hip dysplasia, I can offer some unoffical help. Unofficially, for a limited time, if you forward the x-rays (or a good copy) to me, then a "volunteer" experienced with rating joints for dysplasia will inspect them to see if dysplasia actually exists. This is in effect a free consultation by someone highly experienced and trained in the subject. Obviously, I am trying to protect the identity of the person making this offer so they are not inundated with phone calls or mail by ferret owners by-passing their personal vet, trying to get a free consultation. So inundate me--I will forward all serious inquires, x-rays, and contact information to the proper person(s). Bob C Illustration of the hips can be found in back messages by using the search engine at http://groups.yahoo.com/group/Ferret-Health-list . [Posted in FML issue 3644]