Researchers at the University of Tennessee College of Veterinary Medicine evaluated 30 dogs (4 to 10 years of age and >11 kg of body weight) without a preexisting diagnosis of osteoarthritis (OA) that were admitted for dental prophylaxis. The objective of this prospective observational study was to determine the prevalence and severity of radiographic OA and affected joints in medium and large dogs. In this study, 18 out of 30 dogs (60%) had radiographic evidence of OA. Of those 18 dogs, 16 had 2 or more affected joints. Most dogs with OA had some abnormality on orthopedic examination and clinical examination of stance, walk, and trot. (Lameness was visually detectable in 83% of dogs with OA.)
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Darryl Millis, MS, DVM, DACVS, CCRP, is a professor of orthopedic surgery and director of the CARES Center for Veterinary Sports Medicine at the University of Tennessee, where he has taught orthopedic surgery for over 25 years. We asked Dr. Millis about the primary takeaways from this study and any surprises along the way.
Q: The data indicate a high prevalence of OA in this population of dogs, and the results from the questionnaire suggest that dog owners often do not recognize that their dogs have mobility issues. Veterinarians must be advocates for patients with early OA, and an orthopedic physical examination and lameness evaluation are recommended, in particular to detect bilateral OA that may not lead to gait asymmetry or visually detectable lameness. Would you consider that to be one of the primary takeaways of this study?
Yes, I would. Arthritis is one of the main conditions that affects the quality of a dog’s life; and it is often bilateral, resulting in a relatively symmetrical gait and making lameness difficult to detect because our eyes are looking for gait asymmetry. Unlike in people, arthritis in dogs is often due to a condition that begins in puppyhood, such as hip dysplasia or elbow dysplasia. In midlife, things such as cranial cruciate disease come into play. Most owners think of arthritis as an older dog or human condition, so they are not thinking about this in their 1-year-old dog. Veterinarians must be on the frontline to detect arthritis, advocate for the patient, and educate the owner. Unfortunately, despite a 60% prevalence rate, I suspect most dogs are not screened for OA during routine exams. Further, veterinary curricula seem to be deemphasizing orthopedic training with reduced numbers of lectures and making orthopedic clinical rotations elective rather than required—despite orthopedic conditions being one of the top 3 or 4 conditions seen in practice, according to insurance reports.
Q: In this study, most radiographic changes (59%) were mild/Grade 1. Nonetheless, permanent cartilage damage has likely been done by the time those changes are detected. What can general practitioners do to facilitate the identification of OA earlier?
No. 1, suspect that OA is present until proven otherwise. With more medium-and large-breed dogs having OA than not, look for it and you will find it. Early OA results in subtle lameness, and it may be hard to detect, especially if the condition is bilateral. We must rely on the history and a good orthopedic examination. Ask about some of the items in the owner questionnaire in our study that trigger suspicion of OA, such as difficulty negotiating stairs or rising from a sitting position. Practice, and be comfortable, doing a thorough orthopedic exam. Pay attention to pain with hip extension, effusion of the stifle joint, decreased flexion of the elbow, and pain with shoulder extension. Any abnormalities should be assessed for OA, and treatment should be started. Early identification and treatment may slow the progression of OA in some cases and will certainly put a pep back in the pup’s step!
Q: OA was more common in the pelvic limb joints, with only 2 of the 18 dogs with OA having it limited to their thoracic limbs. This was noted as a surprising finding because osteoarthritic lesions of the glenohumeral joints are often identified after death (studies have reported a prevalence of 32% to 74%). Do you think osteoarthritic lesions of the glenohumeral joints are underdiagnosed?
Yes, I think clinical OA of the shoulder is underdiagnosed. The findings at necropsy in various studies, and our study, suggest that lesions in the shoulder are mainly cartilage erosion without the typical findings of osteophytes seen in other joints. This makes it harder to detect on a radiograph because we only see secondary bony changes and not direct cartilage erosion (cartilage is not visible on a radiograph). Furthermore, dogs seem to handle OA better in some joints than others. For example, it seems dogs do not manifest clinical signs of OA in the shoulder like those in the stifle.
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Q: Knowing that certain breeds, higher body weight, early neutering, and aging have been identified as potential risk factors for OA, what recommendations should be given to clients to minimize the likelihood of OA?
Because OA in dogs is usually secondary to some other condition, such as hip dysplasia, elbow dysplasia, and osteochondritis dissecans, all conditions with a genetic component begin with a good breeding program—screening of the sire, dam, and puppies. Unfortunately, the genetic contribution of these conditions is complex with most having a low heritability index compared to environmental influences. As suggested, early neutering has an influence on the expression of orthopedic conditions; waiting until sexual maturity is reached before neutering or spaying is recommended. Yet this depends on the good stewardship of owners to prevent unwanted pregnancies. Beginning in early puppyhood, the body condition score should be kept to 4–5/9 (or 3/5). It is quite clear that obesity contributes to the prevalence and severity of OA. In one study, the progression of hip osteoarthritis was greatest before 2 years of age in overweight dogs compared to paired littermates kept at ideal body condition scores. After OA begins, you can’t turn the clock back. So, keep young dogs thin and exercise dogs, especially through swimming. Good muscle tone helps to control micromotions of joints and prevents fatigue, which can result in joint injury. (But make sure joints are stable first. For example, the progression of OA in a dog with a cruciate ligament injury is much greater with exercise.)
Q: Were you surprised by any findings from this study?
I don’t think there were any great surprises because our clinical suspicion was that the prevalence of OA was much higher than the widely publicized 20%. But I think the biggest surprise was the high prevalence in a population of dogs that did not have a diagnosis of OA and were not suspected to have OA by their owners. The overall prevalence of OA is probably higher when all dogs are considered. So, we have a lot of work to do, both in diagnosing and treating OA!
Q: Is there anything you would like our readers to know that has not been mentioned?
The major take-home point is to suspect that a dog may have OA, even if that is not a complaint of the owner. Early OA may not manifest as lameness. We must look for it to diagnose and treat this lifelong condition early—before joint destruction and lameness become obvious. Screen for hip dysplasia, elbow dysplasia, and osteochondritis dissecans at 6 to 9 months of age in every large and giant breed dog (PennHIP evaluation can be performed as early as 16 weeks to diagnose hip laxity). Especially with middle-aged and older dogs, ask questions while collecting the history that may suggest the dog has OA. Check the stifles for joint effusion and instability; check the hips and elbows for any discomfort or decreased range of motion. Perform a thorough gait evaluation to check for subtle lameness, including stance and the way a dog sits. If you suspect a dog has OA, it probably does.
Read the full study
Osteoarthritis has a high prevalence in dogs undergoing routine dental prophylaxis.
Millis DL, Hecht S. JAVMA | doi:10.2460/javma.25.05.0330