The joints in our bodies can make a weird and wonderful array of perplexing sounds.
Perhaps you like to crack your knuckles. Or your knees creak when you go up stairs. Or you might have a strange popping sound in your ankles when you run.
But do we need to see someone about those snaps, clicks or crunches? Or are your noisy joints best ignored?
Usually, if there are no other symptoms, you don’t need to lose sleep over noisy joints, says Dr Michael Vagg, clinical senior lecturer in medicine at Victoria’s Deakin University and a pain specialist with Victoria’s Barwon Health.
But there are so many different sorts of sounds, it’s hard to give a blanket answer.
The most common noises are what Dr Vagg calls “benign pops or high-pitched snaps”.
These are thought to occur when the fluid-filled sac within joints gets stretched by a sudden change in position. The resulting pressure and volume change causes gases dissolved in the fluid to form bubbles.
But whether it’s the creation of the bubbles or their collapse that forms the popping sound has been hotly debated.
If you’re someone who loves to crack knuckles, you can take heart that evidence from long-term knuckle crackers suggests it’s harmless (apart from the annoyance to those who don’t like listening to it).
But you don’t have to deliberately crack your knuckles to create these sounds.
Any movement that causes a sudden change in joint volume will do it.
But it has to be rapid; the same movement done more slowly won’t produce a crack.
“For example, my ankle sometimes cracks when I run,” Dr Vagg said.
“It doesn’t crack when I walk. The same movement with a bit more weight on the joint, changes the volume more quickly so it happens.”
Muscle tightness in the neck can also cause these pops: “As you try to turn your neck, there is resistance, which builds up pressure in the joint and then the joint moves suddenly and creates a pop.
Rubbing and grinding
While pops are probably innocuous, other rubbing or grinding noises, known as “crepitus”, can be a sign of damaged cartilage or inflammation.
When cartilage deteriorates it creates a rough surface and can even leave parts of bone exposed, Dr Vagg says.
The creak and grind of crepitus occurs when the rough surfaces or exposed parts of bone rub against each other.
This is osteoarthritis and the noise is most common in the knee and the neck. And it can progress.
Unfortunately, once you become aware of these grinding sounds, there’s little you can do to prevent further cartilage deterioration.
Osteoarthritis is primarily controlled by your genes, although keeping your weight under control can help reduce symptoms.
Confusingly, your degree of cartilage degeneration may not correlate closely with the amount of pain you feel, Dr Vagg says.
It seems to depend on how pain signals are amplified or dampened down in the brain, but no-one’s sure what influences that.
Severely painful crepitus is best checked out by a health professional. In rare cases it can be caused by a fracture; the two broken fragments of bone rubbing together is what makes the noise.
But if worn cartilage is thought to be the cause, you should try to continue to be as active as possible, Dr Vagg says.
This is because cartilage has a poor supply of blood and “relies on movement to milk blood in and out” and so, obtain nutrients.
But it would be wise to minimise high-impact activities — sports like basketball, netball or anything involving repetitive jumping — which can aggravate symptoms and possibly speed up the deterioration in cartilage.
Some forms of painful crepitus might be helped by physiotherapy to correct muscle weaknesses affecting the stability of joints.
Tendons rubbing over bones can also cause crepitus.
This usually happens only when the tendon is quite inflamed from repetitive movement, so you will probably notice the pain before the noise.
It commonly occurs in the Achilles tendon at the back of the ankle — especially in long-distance runners — or in the long tendon in your forearm (often seen in weekend kayakers).
“The sheath of the tendon gets irritated and swells really significantly and you get this real grinding noise. It’s because the tendon is not gliding smoothly in the sheath,” Dr Vagg said.
If this happens, a short burst of over-the-counter anti-inflammatory tablets or rub-on gels may be helpful.
You might also want to try cold packs to help reduce inflammation and speed healing.
You are best to nurse it along by reducing activities rather than giving the tendon complete rest, Dr Vagg says.
And the loudest sound any human joint is likely to make is when the Achilles tendon ruptures. It can sound like a gun being fired because of the enormous tension the tendon is under when it’s released.
“I’ve heard it,” he says of a tennis match he was watching when the injury struck a female player.
“It was incredible. She went down like she was shot. She was in agony.”
The bottom line
The bottom line is that noise plus pain is much more likely to be an indication of a problem needing medical input than a noisy joint alone.
But if in doubt, ask your doctor or physiotherapist to check it out.
Loud, low-pitched clunks can be a warning sign of serious joint problems, especially in children.
“In children, there are some clunks that can be quite important,” Dr Vagg cautions.
Partially dislocated hips that are not diagnosed for instance can wear cartilage out at a very young age, causing life-long disability.
“But if you’re an adult hearing just a bit of crepitus or cracking, it is more likely to be just a bit of getting old.”