Understanding joint health

Joints are amazing pieces of biological engineering

They allow varying degrees of movement between bones in the body.

The basic anatomy of a joint is given in the diagram below.

In reality, the design of joints differ in different parts of the body from the spine to the stifle (knee) or from the cranium to the carpus (wrist). The important components of a joint are given in the diagram below:

All movement in the body requires energy to produce an impulse or signal to be sent along a nerve to cause a muscle to contract. For example, This causes the blink of an eye or the heart to beat.

For locomotor movement, skeletal muscles have firm attachments via their tendons beyond the joints that are required to move. The joint’s direction of movement is dictated by the shapes of the bone ends that fit together and the joint is stabilized by the attachment of ligaments. Lubrication and friction free movement of the joint is essential and this is facilitated by two very important components of the joint: the articular cartilage and the synovial fluid.

Because of the complexity of joints things can go wrong at any level.

Acute problems

Sprains can occur to ligaments and tendons when these strong but elastic structures are stretched too far or fractures can occur to bones when the (abnormal) forces they experience are too much for them to maintain their integrity or if normal forces cause abnormal bones to fail for example, if they have become more brittle with age. Acute problems like these occur quickly and bring about immediate lameness. It is important to take weight off the limb when these occur and your pet will normally do this themselves.

The prognosis is good for such acute conditions provided they are rested (assessed by your veterinary surgeon) and treated correctly.

Chronic problems

An initially more gradual, long term and unfortunately progressive condition can occur with joints, which is known as osteoarthritis (OA).

Previous injury or simply wear and tear can lead to joints becoming inflamed and painful. As the disease progresses it can lead to wear and breakdown of the protective cartilage. This can expose the underlying bone which no longer has a friction-free covering leading to more pain. Fragments of diseased cartilage in the synovial fluid can compromise its lubricating action which can lead to less efficient cushioning of forces and so the whole process can be self perpetuating without veterinary intervention.