What is arthritis ?

16 September 2022

You’ve heard of it, but do you really know what it is? Affecting approximately 20% of dogs over one year old, 60% of cats over 6 years old and 90% of dogs over 12 years old, osteoarthritis is likely to become part of your four-legged friend’s daily life one day. What structures does it affect ? How and why does it develop? How do you recognise it ? Find the answers to your questions.

The structure of a joint

A joint is made up of all the soft parts (such as the ligaments and the joint capsule) and hard parts (the bone and its cartilage) by which two or more bone ends are joined together.

These joints ensure, for the most part, the mobility of our skeleton. They are stabilised by the muscles and their tendons, by the ligaments and, to a lesser extent, by their joint capsule which contains the synovial fluid. This is produced by the synovial membrane and helps lubricate the joint and nourish the cartilage.

Composed mainly of water and cells (called chondrocytes), all held in a framework of collagen and proteoglycans, the cartilage absorbs shocks and helps the bones slide against each other.

A vicious circle

Osteoarthritis is a degeneration of the joint structure. This chronic and irreversible disease evolves in painful attacks. It leads to inflammation of the affected joint, and in an advanced stage to rigidity, loss of muscles and reduced mobility.

The disease begins with the erosion of the collagen framework, the outer layer of cartilage. As the erosion progresses, it loses its qualities, which significantly affects compressive strength. As the chondrocytes attempt to repair the damage, they produce inflammatory molecules that leak out of the erosions, become immersed in the synovial fluid and accumulate in the joint. A cascade of inflammation then sets in and progressively spreads, affecting the various structures of the joint. Also, an imbalance between synthesis and degradation of the cartilage and subchondral bone sets in, allowing both bone growths (osteophytes) and areas of erosion to appear.

A trauma affecting the joint, a chronic inflammatory disease (such as that induced by overweight or obesity), a developmental disorder in young people, an infectious disease, repeated stress or “simply” the natural ageing of the joint: there are many causes of the appearance of osteoarthritis, but it is not always easy to identify them.

Symptoms not always obvious

Osteoarthritis develops slowly and quietly. In the beginning, the signs are discreet and inconsistent. Your four-legged friend may simply give the impression that he has settled down. As the inflammation and lesions set in, he becomes reluctant to run after his ball or join you on the sofa. One day, he may even be reluctant to go for a walk or have difficulty getting out of his basket or even doing his own toilet.

Osteoarthritis is therefore not easy to detect, and this is even more true in cats, who express very little joint pain, even at an advanced stage.

Bibliography:

Radiographic evidence of degenerative joint disease in geriatric cats : This article in the Journal of the American Veterinary Medical Association aimed to determine the prevalence of radiographic signs of degenerative joint disease in cats over 12 years of age.

Understanding the pathophysiology of osteoarthritis : This literature review examines the physical, enzymatic and molecular changes that occur in pets affected by OA.

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The importance of diet for skin and coat quality in dogs and cats

The skin is the body's largest organ, representing between 12% and 24% of the animal's weight, and its surface area in a dog weighing around thirty kilograms is close to one square meter. It's hardly surprising, then, that the quality and quantity of the dog's diet can have an impact on this organ, and in the event of a deficiency can lead to problems that go far beyond a simple visual appearance.

Key nutrients for healthy skin and coat

Among the macro-nutrients, proteins play a crucial role. They provide amino acids, including sulphur amino acids, which are essential for the structure of the skin and coat. These are the main components of collagen, which gives the skin its suppleness and resistance, and of keratin, which plays a part in the effectiveness of the skin barrier. Lipids are also important; they make up the bulk of cell membranes and, in the skin, contribute significantly to the effectiveness of the cutaneous barrier. Among lipids, omega-3 and omega-6 fatty acids help maintain healthy skin, modulate inflammatory mechanisms and promote a shiny, soft coat. Vitamins and minerals are also involved. Vitamin A is necessary for cell renewal, as is vitamin D, which also plays a part in the skin's natural defences. Vitamin E acts as an antioxidant, while B vitamins and biotin are essential co-factors in the synthesis of various skin elements such as ceramides, keratin and collagen. Among the minerals, zinc is involved in synthesis, protection against free radicals and immune defence mechanisms.

Disorders linked to inadequate nutrition

Inadequate or poor-quality food can lead to skin problems in our pets. A deficiency in essential fatty acids leads to dry, flaky skin, a dull coat and brittle hair. When it's the vitamins and minerals that are in short supply, synthesis is affected, the skin barrier can be less effective and the breeding ground for infections and inflammations that can lead to itching. On the other hand, these nutritional benefits can be used to compensate for individual sensitivities and improve the quality of the skin and coat in the event of dermatological disorders or diseases.

Conclusion

The quality of a dog's skin and the beauty of its coat are directly influenced by the quality of its diet. However, some dogs and cats have increased needs, and it is therefore necessary to provide them with greater quantities of useful nutrients. This is particularly true in the case of certain dermatological disorders, to help compensate for imbalances and accompany the medical treatments prescribed by your vet.