Part 1: The Disease
Arthritis tends to be a fact of life for many of our older pets. Current statistics indicate that 20% of dogs over the age of one year have some degree of degenerative joint changes that lead to arthritis and 90% of cats over the age of 12 have evidence of arthritis on radiographs. The cause is simply progressive damage to the joints over the life of the pet – some pets are predisposed to a faster onset of the condition due to conformation (bone structure), others due to obesity and still others due to high impact activity over a long period of time. These lead to stress damage to the joints at a cellular level.
Joints are fluid filled sacs between bones lined with cartilage – a tough substance that cushions impact and has low friction surfaces to allow free movement of the bones within a certain range of movements. Joints have certain predefined shapes depending on the range required. Examples include ball and socket (hips, shoulders), hinge-type (elbows, knees) and fibrous (vertebrae). The carpal or wrist is more complex involving multiple joints between several smaller bones.
Damage, stress or instability within a joint causes subtle changes in the structure of the cartilage that builds up over time. The changes result in a loss of the cushioning and increased friction; the more it progresses, the more we start to see inflammatory changes. Gradually the cartilage becomes more damaged and loses some of its protective properties. Towards the later stages we see modification in the bone structure with proliferation and roughening of the bone at the joint margins.
This is all very technical: what we see in our pets is stiffness and decreased mobility. Often, the day after a long walk our dogs will take a lot longer to get up and start moving in the morning. Both cats and dogs may avoid jumping as much as they used to and will become more sedentary. In some cases we may see a visible lameness or a change in the pet’s gait and hesitation going up and down stairs. In humans, we have a number of ways of reducing the pain and inflammation to improve mobility and the same is true of pets.
by Dr. Gawen Thompson
