Author: Primrose Moss
Primrose Moss shares an insight into this prevalent cause of chronic pain in the first of this two-part series.
Arthritis is a prevalent cause of chronic pain in dogs, affecting up to 20% of dogs over one year of age. The early symptoms can be subtle, with many cases going undiagnosed for a long time. While it can’t be cured, early diagnosis and management of arthritis can significantly impact dogs’ quality of life. So, what exactly is arthritis, and what can we do about it?
What is arthritis?
Arthritis is a general term used to describe inflammation of the joints. This includes infectious and immune-mediated forms of arthritis. However, the term arthritis is most commonly used to refer to osteoarthritis, which is by far the most common form and is the focus of this article. Osteoarthritis (referred to as arthritis for the rest of this article) is a degenerative joint disease that affects a large proportion of primarily elderly dogs (and cats). However, it can occur in younger dogs.
Unlike humans, dog arthritis usually results from an underlying problem rather than a primary disease (i.e., it’s not usually caused by just wear and tear). It’s the ‘common endpoint’ for a whole range of different underlying problems, all of which contribute to the eventual degeneration and inflammation of the complex joint structure. It can affect just one or multiple joints and often affects joints bilaterally (e.g., both hip joints).
One of the critical components of arthritis is the erosion and breakdown of the cartilage that covers the bones’ ends, causing friction during movement; however, many other complex interactions and inflammatory molecules are involved. Arthritis is also characterised by the formation of small bits of new bone at the edges of the joint, which sometimes break off and float within the joint space.
These cause the ‘crunchy’ feeling (crepitus), often palpable when affected joints are moved through their range of motion. Arthritis is a slowly progressive disease that can’t be cured – but the good news is that it can be managed effectively, and its progression slowed, with many affected dogs living long and happy lives. As always, prevention is better than cure, so if your dog is young, it’s still worth reading on to find out how you can reduce the risk of arthritis later in life.
What causes it?
The causes of arthritis can be broken down into a few categories:
- Normal wear on an abnormal joint – e.g., dogs with underlying joint dysplasia.
- Abnormal wear on a normal joint – e.g., secondary to an injury, excessive very high-level exercise or the increased load on joints caused by obesity.
- Abnormal wear on an abnormal joint – a combination of the above.
- Normal wear and tear on a normal joint – this is not believed to be significant in dogs, unlike humans.
Due to its prevalence in older dogs, it’s a common misconception that arthritis is mainly due to wear and tear. While this contributes, the evidence suggests that dogs with normal, healthy joints performing typical daily activities are unlikely to develop arthritis solely due to age-related wear and tear. So, what are some of the causes of either abnormal joints or wear?
Joint dysplasia
Joint dysplasia describes the abnormal development of one or more joints. It’s mainly seen in large, giant dogs, primarily the hips and elbows. It’s not a congenital condition, as it develops during growth, but it does have a strong genetic component. Labradors, for example, are commonly affected by both hip and elbow dysplasia. The dog’s size, growth rate, excessive feeding and exercise are also thought to contribute.
Dogs affected by hip dysplasia are born with normal hips, but increased laxity develops at around 4-5 months of age, allowing the head of the femur (the first leg bone) to shift out of the hip socket slightly. This shifting creates inflammation and causes the joint to remodel, creating a permanently abnormal joint.
Owners may notice some lameness as the joint remodels, but dysplasia is often not picked up on until later in the dog’s life when secondary arthritis develops. A similar process of abnormal joint development occurs in dysplastic elbows and shoulders, with symptoms beginning at 4-8 months of age. If dysplasia is detected in a young dog, surgery may be possible to correct it; alternatively, conservative treatment can help to minimise long-term problems and delay the progression of subsequent arthritis. Pre-breeding screening programmes run by the British Veterinary Association and UK Kennel Club are essential in reducing the rate of hip and elbow dysplasia in some breeds.
Injuries
A past injury can contribute to arthritis through direct joint damage (for example, a fracture affecting the end of the bone) or through chronically abnormal loading (e.g. shifting weight onto one leg to reduce weight bearing on the other). For example, ligament damage, like cruciate ligament disease, can also contribute via joint instability.
Patellar luxation
Patellar luxation, where the kneecap ‘flicks’ in and out of its groove on the front of the knee, is common in small breeds like Jack Russell Terriers. In many cases, it doesn’t cause significant lameness and is often not painful, but the abnormal movement predisposes affected dogs to secondary arthritis. In severe cases, surgery may be recommended earlier in life to correct the movement of the patella and minimise this risk.
Obesity
Last but by no means least, obesity is a significant cause of arthritis in dogs. It’s easy to see how obesity increases the load on joints and can worsen arthritis, but the full picture is a little more complex. Starting at a young age, excessive weight gain in puppies have been correlated with joint dysplasia and subsequent arthritis. As they age, it’s been suggested that being overweight or obese not only places excessive load on the joints but also increases levels of inflammatory molecules within the body, which may also contribute to the development of arthritis.
Once arthritis has developed, a vicious cycle of weight gain due to lameness and reduced activity often begins; however, this doesn’t need to be the case. The primary driver of obesity is excessive calorie intake, so a controlled diet can keep these dogs in good condition and reduce their pain. One study of obese dogs with arthritis showed an improvement in lameness when dogs lost 6-9% of their body weight.
How can you tell if a dog has arthritis?
First things first – dogs with painful arthritis rarely yelp, cry or ‘tell us’ they’re in pain. In severe cases, they may become reactive to touch or vocalise in response to an excruciating movement, which is relatively rare. For most dogs, arthritis is a slow, insidious, progressive condition. Owners often report that their dog is ‘just slowing down’ due to age rather than pain. Nobody
“For most dogs, arthritis is a slow, insidious, progressive condition.”
wants to think they’ve missed signs of pain in their beloved pet, so there’s sometimes an understandable resistance to accepting that the signs you thought were ‘just old age’ may be pain related. However, the sooner arthritis is detected, the better your dog’s quality of life can be.
Notably, many arthritic dogs, especially in the early stages, will still be very keen for walks and may tear around when excited just like they always have – but they’ll often pay the price for this behaviour later that day or the next day, once the excitement is over. The inflammation and pain have had a chance to develop. Diagnosis of arthritis is typically based on the history and a physical examination, although X-rays are sometimes helpful for confirmation or to rule out other problems. For conditions like joint dysplasia, x-rays and CT scans are more beneficial to identify whether further interventions might be required.
Reproduced with permission from one of our favourite partners Edition Dog, Issue 64 2024, Author: Primrose Moss - find out how you can read more amazing canine content at Edition Dog
