A recent Australian study has found that “knee crepitus” – or creaky knees – is “common across all age groups”.

Overall, 41 per cent of Australians experience creaky knees – the crackling, clicking and grinding sounds made in the knee joint as one moves about – at least sometimes.

For many people, the cracking and popping isn’t accompanied by pain. But the sounds are disturbing enough to make them afraid of exercising.

La Trobe University graduate researcher and physiotherapist Jamon Couch said people with creaky knees “often felt there were more serious underlying health issues like arthritis, causing them to be fearful of exercising and using their knees”.

According to the National Library of Medicine analysis, they’re scared of putting more strain on their joints and “wearing them down” even more.

But they’re actually potentially damaging the joints if they aren’t used enough. Knees need to be exercised, even when blighted with osteoarthritis.

First, exercise increases the blood supply and metabolic processes, and supplies the joint fluid with nutrients. Second, exercise allows the joint fluid to enter the cartilage in the joint.

The cartilage “squeezes together like a sponge and releases waste products when under strain, and it absorbs nutrients from the joint fluid when released”.

This is a problem. Exercise keeps the blood going to the joint.

What causes ‘creaky knees’?

Couch said the cause of knee crepitus “has been debated for decades, yet current evidence cannot confidently determine exactly why it occurs”.

Medical News Today says it usually happens when air bubbles develop in body tissues.

The popping sound “usually comes from air seeping into the soft tissue, finding its way into the area around the joint and causing tiny bubbles in the synovial fluid”.

When a person bends or stretches their knees, the bubbles can burst with a popping or cracking sound.

It can also happen when the tendons or ligaments snap over the bony structures in the knee.

More seriously, the crunching is a result of patellofemoral pain syndrome, otherwise known as ‘runner’s knee’.

This occurs when “the pressure between the kneecap and the femur is greater than usual, the cartilage in the joint can start to soften and wear away”.

Creaky knees can also occur with torn cartilage, or osteoarthritis.

The latest study

The research, published in the British Journal of Sports Medicine this week, analysed the results of 103 studies involving more than 36,000 people and found that 41 per cent of the population had creaky knees.

(Whether or not this includes babies wasn’t made clear.)

Couch said that knee crepitus “was common in those with and without a knee injury”.

The researchers discovered “that 36 per cent of people without a knee injury had creaky knees”. However, “it was far more common in those with an injury to their knee cartilage”.

They found that knee crepitus was present in 81 per cent of those with knee osteoarthritis. For some people, creaky knees might be an early symptom of osteoarthritis.

“People with knee crepitus were more than three times as likely to be diagnosed with osteoarthritis,” Couch said.

He said investigation of the long-term consequences of knee crepitus was ongoing.

“People should generally not be concerned about their noisy knees.”

They should in fact “be encouraged to continue to exercise”. If it’s not painful, “it’s likely not doing any damage”.