Osteoarthritis is an ever-increasing medical condition within the canine community. According to an article published in the January 2021 Journal of the American Veterinary Medical Association (JAVMA), in dogs, unlike humans, osteoarthritis actually tends to start at a young age. This viewpoint is actually a deviation from the previous veterinary perspective wherein osteoarthritis was said to be a degenerative disease of older dogs, exacerbated by obesity.

In fact, it is now asserted that osteoarthritis in dogs mostly results from developmental problems. One of the professors featured in the article specifically stated, “Osteoarthritis is a young dog’s disease.” The inference is that these developmental problems are inherited.

At the AVMA Virtual Convention 2020 in August, professors from two veterinary colleges gave talks about treating canine osteoarthritis effectively—including by using a new staging tool—and integrating new types of treatments for pets with osteoarthritis. These experts say earlier diagnosis and treatment are pivotal to managing both the pain and the progression of the disease. The experts assert pain starts in younger dogs because due to developmental orthopedic problems, they adapt their posture to continue daily living activities. The pain results in deleterious effects such as musculoskeletal deterioration, central sensitization, and cognitive and affective decline. All of these result in increased resistance to treatment. As a means to counter these changes, the experts have developed a Canine OsteoArthritis Staging Tool (i.e., COAST).

According to the JAVMA article the four pillars of treatment for osteoarthritis in dogs are an effective analgesic such as a nonsteroidal anti-inflammatory drug, weight optimization, diet optimization, and exercise. The treatments are interdependent. An effective analgesic decreases pain, which allows for an increase in exercise. Exercise contributes to weight management, and exercise and weight management together decrease pain. Finally, a decrease in pain allows for a decrease in the analgesic requirement. Surgical correction of joint deformity is considered only when medical management has failed.

The JAVMA article refers you to additional information about the COAST and how to incorporate it into your veterinary practice. The additional COAST information brings you to an extensive advertisement to promote the use of a new nonsteroidal anti-inflammatory drug, Galliprant, marketed by Elanco Animal Health.

Healthy and Happy Dog acknowledges osteoarthritis is a problem that is being observed in young dogs today. It starts for many dogs with functional adaptations made to accommodate physical deformities that are developmental. The inference in the JAVMA article is that these developmental problems are inherited or genetic in nature. There is no mention of early spay or neuter in this article. It should have been noted that for inherited orthopedic conditions, such as hip and elbow dysplasia, or the predisposition for cranial cruciate ligament tear, removing the gonadal hormones that regulate the duration of bone elongation would be expected to alter growth patterns and subsequent joint alignment exacerbating any preexisting heritable propensity for disease.¹⁸³ 

Even if a dog has no genetic predisposition for developmental orthopedic problems, spay/neuter prior to developmental maturity will significantly increase the risk of orthopedic joint deformity/disorders. The defining issue is how spay/neuter affects the dog’s hormones. When a dog’s reproductive organs are surgically removed, the “sex hormones” they produce in large part disappear, at least temporarily.  The sex hormones are responsible for more than just sexual behavior. In fact they are known to affect bone and muscle, and one of their responsibilities is regulating growth.^60,61,89,108

On the Orthopedic Disorders page, we include a summary of the studies at UC Davis published in 2014  ⁶¹, 2016¹⁰⁸, and 2020¹⁸¹, as well as the findings of the Golden Retriever Lifetime Studies ²²² which all indicate that early spay/neuter significantly increases a dog’s propensity to develop hip dysplasia, cranial cruciate ligament tear, and elbow dysplasia. This analysis was deemed logical for pathophysiological reasons because a disruption of the growth plate closure by gonadal hormone removal in the joint developmental stage would be expected to apply to all the joint disorders.

Additionally, independent of the joint disorders, a spayed/neutered dog will have a greatly increased likelihood of becoming obese. The aforementioned studies, as well as a 2019 review, summarize the effects of spay/neuter on cancer, orthopedic, and immune disorders and evaluate the relevance of body weight. The 2019 review of the relevant research confirms that with respect to orthopedic joint disorders, weight did not exacerbate nor ameliorate the risk associated with spay/neuter.¹⁸³

The previous theory that veterinarians espoused was that obesity was responsible for the prevalence of osteoarthritis. The new viewpoint in the JAVMA article is that developmental orthopedic problems are more relevant to the development of osteoarthritis than is obesity. This new theory is consistent with the latest studies; the issue is that the JAVMA article fails to include early spay/neuter as the most prevalent reason for developmental orthopedic problems. Failure to include that information is unconscionable.

Expanding upon the problem of osteoarthritis is the failure of the JAVMA article to address the prevalence of osteoarthritis even after the developmental problem has been corrected surgically. On the Obesity page, we point out that in dogs that are not overweight, osteoarthritis often follows injury even if a reparative procedure is performed. Using dog Billy as an example, although he was at an ideal weight, he still sustained a  cranial cruciate ligament tear which required TPLO surgery.

Unfortunately, his TPLO surgery did not prevent arthritis in the repaired joint. In fact, studies show arthritic changes start almost immediately after surgery.⁶⁴  The American College of Veterinary Surgeons confirms rupture of the CrCL  is one of the most common reasons for hind limb lameness, pain, and subsequent knee arthritis.

The salient point is that rupture of the cranial cruciate ligament generally occurs as a result of improper bone growth due to a deficiency of sex hormones during development. Obesity is not responsible for an orthopedic deformity such as this. Building upon the JAVMA theory regarding canine osteoarthritis, why would a dog develop osteoarthritis after reparative orthopedic measures are implemented? Could deficient sex hormone levels affect healing after reparative surgery? Apparently so.

Utilizing the “Canine-Human Connection“, we looked to see if research on humans took into consideration sex hormone levels when evaluating the incidence of osteoarthritis. With respect to humans, in addition to age, obesity, genetics and other factors, Medscape specifically lists “reduced levels of sex hormones” as a primary risk factor for osteoarthritis. Interest in estrogens was stimulated by the dramatic rise in osteoarthritis prevalence among postmenopausal women. Research is ongoing to obtain a better understanding of the role that estrogen and its deficiency plays in menopause-induced osteoarthritic changes. Both experimental and observational evidence support a relevant role for estrogens in the homeostasis of joint tissues and, hence, in the health status of joints. ¹⁷⁸

A study published in the journal Arthritis and Rheumatism ¹⁷⁹ looked at how sex hormones (estrogen and testosterone) can affect people with osteoarthritis. In this study, researchers wanted to look at chondrogenic progenitor cells (CPCs). These cells are in tissue that’s affected by osteoarthritis, and they can help the tissue regenerate itself – if they’re activated by sex hormones.

The researchers found putting estrogen or testosterone into the tissue cell did increase the regenerative properties of the CPCs. Tissue from women was most influenced by estrogen; tissue from men was most influenced by testosterone.

Applying the results of human studies to our canine companions, it does appear that a deficiency of sex hormones in spayed/neutered dogs may enhance the development of osteoarthritis. Injured cartilage cannot regenerate or heal in the absence of adequate sex hormones. In cases of injury like CCL tear, even if reparative procedures are undertaken (e.g. TPLO surgery), the absence of adequate sex hormones precludes regeneration/healing of cartilage in the affected joint, and osteoarthritis is the unfortunate result.

Sadly the failure by the veterinary community to acknowledge the underlying issue of hormone depletion and its association with osteoarthritis will interfere with the prevention of osteoarthritis, as well as the optimal treatment of osteoarthritis. Further, the premise of the JAVMA article that dogs are not like humans with respect to osteoarthritis is a violation of the Human-Canine Connection. Remember, dogs are typically utilized in studies to benefit humans, and that would include cardiovascular studies, heart and lung research, genetic studies, age-related research, pulmonary studies, cancer research and orthopedics (e.g., the development of prosthetic devices for hip and knee replacements, vertebral fusion models, cervical disc degeneration). Recently, MRI studies ⁸⁵ have established that our dogs’ brains work much as ours do. There is no reason to believe that osteoarthritis is the one circumstance where dogs differ dramatically from humans, and there are no credible studies to back up this theory promulgated in this JAVMA article.