Why is that some joints, in some people, wear out quicker than others? I’ve seen people in their thirties with joints that when X-rayed or scanned look twice their age. Yet they have not suffered any previous injury, or other condition to explain such a premature deterioration. Similarly we often see people who have significant damage to the joint on one side, but much less on the other. Clearly simple ‘wear and tear’ is not sufficient to explain this, a problem doctors and scientists have wrestled with for years. They have looked at the structure of the bone and cartilage to see whether some people are more durable than others, whether other disorders make them more likely to develop arthritis and they have even explored a number of other possibilities, such as a genetic disposition.

As we might expect all these factors have their place, as does one of the more recent discoveries, called biomechanics. It sounds and is a complicated subject but a very important one that we will all hear more and more about in the next few years. Seemingly minor problems like one leg fractionally shorter than the other, a damaged tendon or ligament that heals marginally weaker than it was, or a problem in the spine that twists the pelvis may all cause minimal but important stresses on the skeleton that the body reacts to by making movement compensations. This produces further, opposing stresses which progressively distort and over time can damage the bones and their cartilage. What starts as a minor problem often unnoticed, progresses to painful disabling arthritis.

The problem with ‘wear and tear’ is that it sounds inevitable, and therefore tempting to do nothing about, especially in the early stages. Across the whole of medicine one piece of advice recurs. Don’t leave it too late, and this is as true here as anywhere. Since terms like wear and tear, or joint degeneration, are not very accurate descriptions of the underlying causes of arthritis, we would all do well to heed joint pain or disability early, when the treatment options are greater and the possible outcomes better.