Page 9 - Chiron Autumn 2018
P. 9

   This article is the first in a two part series that will look at Osteoarthritis (OA), in the dog. This article will cover the risk factors, root causes and diagnosis of OA in dogs, whereas the follow up article will cover treatment options including holistic lifestyle changes and pharmaceutical interventions. The aims of the articles are to raise awareness of the condition, improve the knowledge of the general dog handler/owner and increase the welfare of affected dogs.
A simple definition of OA is the degeneration of cartilage or bone causing pain and stiffness.
OA may affect up to 20% of all dogs in the UK. One interesting risk factor for the diagnosis of OA is having your dog insured. This is likely a demographic influence as more affluent owners are more likely to cover the cost of radiographic (x ray), diagnosis. It is likely however, that OA is under diagnosed as there are no national studies to record this.
Many breeds including the Labrador Retriever, German Shepherd and Springer Spaniel have been shown to be at risk of developing OA, as well as generally larger breed dogs are more at risk. Many people believe this to be largely influenced by weight with heavier dogs being more at risk. The figure to the right shows some normal canine hips on x rays.
The effect of obesity is well understood as a factor influencing OA. Think of each joint (elbow/hip etc), to be a load bearing structure. When comparing two identical structures the structure bearing more weight will fail first. Conformation defects such as Elbow or Hip dysplasia will also affect the load bearing capacity of the structure. Combine a heavier weight through an already defective structure and it is obvious that the structure will fail, or in this analogy OA will start to develop. The x ray below shows a young dog with a severe conformation defect (hip dysplasia), that has led to an early onset of osteoarthritis. The ball of the joint does not fit into the socket and the socket is misshapen. Progressive damage to the joint has lead to bony changes in and around the joint which inevitably leads to pain.
As with people trauma to a specific joint, whether that be surgery to correct a defect (rupture of the cranial cruciate ligament), or a traumatic break, is a common cause of OA . Neutering of animals may also have an effect but it is unclear as to why this happens.
Two theories are proposed, the first being that neutered animals are far more likely to become overweight and as discussed this is a risk factor towards the development of OA. The second is that the sex hormones may have a protective effect on cartilage. The benefits of neutering females not destined for breeding far outweigh any risk but the neutering of males is equivocal in terms of medical benefits. Neutering does not affect drive to work or aggression
levels with correct positive reinforcement training procedures.
Preventing OA is largely weight management. Regularly weighing your dog will help to track any changes, as is condition scoring. The World Small Animal Veterinary Association (WSAVA), has an easy to find condition scoring chart that is readily accessible. Dog should aim to be condition score 4 or 5. Where condition score or weight is increasing, decreasing rations and repeating the condition score/ weight check at regular intervals will help to maintain this.
The World Small Animal Veterinary Association (WSAVA), has an easy to find condition scoring chart that is readily accessible
Where young dogs are showing signs of lameness in specific joints (elbow or hips), congenital conformation defects should be suspected and investigated with x rays as a minimum. Elbow dysplasia does not always show up well on x rays and so further imaging either CT or arthroscopy and corrective surgery is required for certain problems.
This images to the right are of a six month old Labrador Retriever. The growth plates have not yet closed hence the fracture like appearance on the back part of the elbow.
Images A, and B to the right show subtle changes indicated by the white arrow suggesting underlying pathology. Image C does not show huge changes. D and E are the CT scan of the same below showing a fragmented part of bone in the elbow of the same dog. F shows the bone with the human eye using an arthroscope. Arthroscopy was then used to remove the fragment. If missed this would have lead to an early onset of OA at a younger age.
Readers should now have an appreciation of the condition OA and readers should have an idea of the risk factors and diagnosis plan. Diagnosis is not always straight forwards as the images above prove. The next article will look at treatment options and possible prevention.
The x ray below shows a young dog with a severe conformation defect (hip dysplasia), that has led to an early onset of osteoarthritis. The ball of the joint does not fit into the socket and the socket is misshapen. Progressive damage to the joint has lead to bony changes in and around the joint which inevitably leads to pain. Courtesy of Fitzpatrick Referral.
Osteoarthritis (OA) in the dog
Capt James Wright BVSc CertAVP PgC VPS MRCVS
     Images A, and B to the right show subtle changes indicated by the white arrow suggesting underlying pathology. Image C does not show huge changes. D and E are the CT scan of the same below showing a fragmented part of bone in the elbow of the same dog. F shows the bone with the human eye using an arthroscope. Arthroscopy was then used to remove the fragment. If missed this would have lead to an early onset of OA at a younger age. Courtesy of Villamonte et al, 2015.
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