Is Animal osteoarthritis different from that of humans? We’re told that many people have a lot of osteoarthritis with little or no pain, while others have little osteoarthritis but a lot of pain. Is it because humans have different levels of pain sensation?

This question is related to this post on Facebook.

Osteoarthritis is a condition that compares favorably from one species to another, at least in mammals, and this includes humans. We speak of translational value, e.g. from dog to human, and vice versa. A study (Gordon et al. 2003) on 41 dogs reported a lack of correlation between the level of structural damage (radiographic) and pain perception (assessed by podobarometric gait analysis). The latter is recognized as a standard (reference) measure in arthritic dogs and cats, and consists of a measurement of the ground reaction forces generated by each step and each leg of the animal. The authors concluded that pain levels in dogs could be high in the presence of little damage, and vice versa. So it seemed to fit well with what you’re reporting.

However, in 20 years, knowledge of osteoarthritis pain has evolved enormously, and we now understand that not all pain stimulation will be integrated in the same way by each individual. What happens is that this stimulation will trigger a series of inhibitory and/or facilitatory controls which will determine a genuine pain signature. If inhibitory controls are effective, then pain perception will be low, even in the face of severe joint damage. Conversely, small lesions can generate a highly facilitated signal, accompanied by a high pain perception. With prolonged stimulation, it appears that said inhibitory controls fatigue, and so we end up with severe pain, and a sensitized patient profile. This is why a certain percentage of human patients (around 15%), even after receiving a corrective joint prosthesis, continue to perceive a high level of pain. These are exactly the same phenomena we find in our arthritic veterinary patients!

Better understanding of osteoarthritis pain will ultimately benefit both our pets and their owners, as new pain relief developments target this awareness and improve its control by the best analgesic available – the one produced by the body.