Can doing a lot of exercise wear out your joints?

A: Usually not. In most cases, exercise does more good than harm to joints.

Have you got creaky knees or achey hips? Do you grimace every time you have to climb a set of stairs?

Everyday movements can become a chore when the cartilage in your joints starts to break down, making them stiff and sore.

Sore joints are the hallmark of the condition known as osteoarthritis. And since it's increasingly common as we age, it's easy to assume a lifetime of activity is to blame.

But is this really the case? With every movement our limbs make, are we literally wearing our joints away?

No, says Sydney arthritis expert, Professor Patrick McNeil.

Plenty of older people who've been active all their lives never develop osteoarthritis, he points out.

And the idea our joints are like car tyres or light bulbs with a limited number of "uses" before their lifetime expires is simply untrue, McNeil says.

"I think it's a myth to make the general statement that exercise is bad for your joints or actually wears your joints out. There's no evidence for that."

Injuries and arthritis

But the relationship between exercise and cartilage loss is complex. For most people, exercise helps joints stay healthy. But in some instances, it could be harmful, McNeil says.

When the alignment of a joint is incorrect – perhaps because of weakened muscles or because you were born with unusually shaped joints – it's feasible movement might have some role in wearing cartilage away. But a person may also need to have a genetic predisposition for this to happen.

"You could be born with cartilage that will last, no matter what you do to it. Or you could be born with cartilage that's less durable."

And even if your joints are perfectly aligned, this can change after an injury.

Sports that expose joints to extreme forces, making injuries more likely, are known to raise the odds of joint trouble down the track.

For instance tears to the anterior cruciate ligament (ACL) – a major ligament in the knee – carry a 70 per cent risk of osteoarthritis within 10 to 15 years.

Even when the ligament is surgically repaired, the initial injury changes the stability of the knee permanently, so that over time it's more likely cartilage will break down.

The top three most risky sports for ACL injury are soccer, Australian football ("Aussie Rules") and netball.

Fortunately, exercises that strengthen key muscles around joints can reduce the risk of ACL tears and other injuries that predispose to arthritis by as much as 60 per cent. (For more info on these exercises read: Fighting sporty kids' arthritis risk.)

It's also worth noting that the processes leading to cartilage loss may be different in different parts of the body.

Osteoarthritis of the hands for instance seems to have a very strong genetic basis.

"Exercise doesn't seem to be relevant at all to osteoarthritis of the hands," McNeil says. "If use was a factor, you'd expect right-handed people to have more arthritis in their right hand than in their left. But that isn't the case.

"We still don't understand all the triggers."

More to gain than to lose

The bottom line is that the evidence so far doesn't suggest a strong connection between simple repetitive use of a joint and the development of osteoarthritis.

So if your joints aren't bothered by the exercise you're doing, it's unlikely you're doing them harm, McNeil says.

But if you have already been diagnosed with joint damage, or have pain that suggests it, it's possible the wrong sort of exercise could make your arthritis worse.

"If you have osteoarthritis in weight-bearing joints such as the hips, knees and lower spine for instance, high impact exercise like running can certainly aggravate symptoms and it's probable it might accelerate progression [of the damage to the joints], although I think that's still an open question," McNeil says.

"In those cases, I'd probably recommend a lower impact exercise such as swimming or bike riding that puts less stress on the affected joints."

However, stopping exercise altogether isn't recommended; it's actually one of the best treatments for arthritis, McNeil says.

Cartilage is living tissue but it does not have arteries that deliver blood. Instead it relies on movement of the joint to create a pumping action that circulates fluid containing oxygen and nutrients.

Exercise also:

·         decreases pain.

·         helps maintain the mobility and flexibility of joints.

·         improves muscle strength, which can help hold joints in their correct alignment, taking pressure off sore spots.

The other very important benefit of exercise is that it helps you maintain a healthy weight. Excess weight increases the risk of osteoarthritis by placing stress on joints (and possibly by inducing chemical changes in the body as well).

And of course exercise has proven and very significant general health benefits for everyone – whether they've got existing joint troubles or not.

"It's much better to be physically active than to hold back because of your joints," says McNeil.

Professor Patrick McNeil is a rheumatologist and the president of Arthritis Australia. He spoke to Cathy Johnson of the Australian Broadcasting Corporation in June 12, 2012.