Is it okay if your knees make noise when you work out?

Short answer

Noise alone was not a cause for concern. 36% of pain-free people had noisy knees, and the noise was not linked to function, pain, or knee replacement within 3 years. Its link to arthritis showed up mainly in knees that already had joint changes.

Is it okay if your knees make noise when you work out?
'Knee noise → worn cartilage → arthritis' — does this formula hold?
Many people say that popping or grinding in your knees during squats or stairs is a sign of cartilage wearing away. We checked how common knee noise is and whether it is tied to joints actually getting worse.
How common is knee noise?
Even 36% of pain-free people had it
An analysis that pooled 103 studies and 36,439 people found knee noise in 41% of the general population. Among people with no knee pain at all, it was 36%. More than one in three people deal with noisy knees.
Do noisy knees work worse?
Noise was not linked to function or pain
Researchers compared 165 people with pain at the front of the knee and 158 without. Noise was 4.19 times more common in the pain group, but within that group, noise was not linked to function, activity level, pain after 10 squats, or pain after climbing 10 stairs.
What about arthritis?
The link was strongest in knees that already had changes
In the same analysis, noisy knees had 3.79 times more arthritis on X-ray. In a 4-year study of 3,495 people with an average age of 61, knees that always made noise had 3.0 times the rate of arthritis with symptoms, but over 75% of new cases were in knees that already showed changes on X-ray.
Do noisy knees end up in surgery?
No link with knee replacement within 3 years
In a study following 4,566 people, knee noise was not linked to knee replacement within 36 months. Noisy knees lost 2% more knee-straightening strength over 4 years, but physical function and quality of life showed no difference.
What about injured knees?
Noisy knees did not get worse over 5 years
112 people were studied 1 year after knee ligament (ACL) surgery. Noisy knees had 2.7 times more cartilage damage behind the kneecap, but arthritis changes did not worsen more between years 1 and 5. Pain and function actually improved more.
Is it linked to thigh muscle?
Louder noise came with thinner front thigh muscle
Ultrasound in 60 people with front-of-knee pain showed that the more severe the noise, the thinner the front thigh muscle. But simply having noise or not was not linked to muscle thickness or knee-straightening strength. Having noise or not did not separate weaker muscles from stronger ones.
Summary: knees that only make noise are common
It is a different story when pain or loss of function comes with it
36% of pain-free people had noisy knees, and the noise was not linked to function, pain, or surgery within 3 years. The link to arthritis was strongest in knees that already had changes. For knees that only make noise without pain, no result pointed to stopping training.