For many, the clicking and clunking of their joints as they hurry around a football pitch is a pretty normal occurrence.
For some, it could even be the first thing they hear when they get out of bed on a morning.
Sit inside the dressing room of any Sunday morning football team this weekend and there will be at least a few players complaining of this type of thing.
Sit inside the dressing room of an over 40's team and the chances of it happening have probably increased ten fold.
Clicks and clunks in knee joints are where these sounds are particularly audible and some people even take great delight in trying to reproduce the sound to an audience.
To any one who will listen, family, team mates, or even a physio, the clicking and clunking is often proudly displayed and for some grassroots players is nothing more that an inevitable consequence of years of twisting and turning.
The question of "why does my knee click"? is one of the most popular I get inside my physio room from my patients and is one of the easiest to understand.
It's wear and tear in your joints.
The knee joint is designed to offer support and cushion and even absorb the shock it receives from the impact of hard surfaces or twisting repeatedly.
But over time, and as you clock up the games, this cartilage wears thin and instead of the ones in your knee rubbing softly against each other, somewhere around the age of 40 these bones are now rubbing directly against each other.
And because these bones are very tough and very hard, inevitably it causes a noise.
It can also happen because the muscles in your leg become weak.
When a muscle is not as strong as it could be, the knee cap isn't held in the right position and it to can clunk and crack its way into and out of position as your knee bends. Still, its pretty normal and very common.
But the noises aren't necessarily associated with pain. It's often just the first sign that trouble is on the way.
Eventually the bones clunking and rubbing together will have the same effect as two bits of sandpaper rubbing together and you could end up with rough surfaces and even holes in the bones.
This is where the pain sets in and your knee begins to swell and will take longer to recover after games.
The next step for the grassroots player is to opt for the knee support and this will help, but only for a while.
Inevitably these things have a habit of getting more and more painful and eventually the only option is to go under the knife with a surgeon and have the knee cleared out with keyhole surgery.
Cartilage injuries are pretty common in the professional game too. Hartlepool United's Jordan Richards last week went under the knife for a cartilage problem and is likely to be out for the remainder of the season.
Because of his young age, it's very unlikely that he is suffering from the degenerative type of knee problem I've just described, although it is possible in rare cases.
Somebody in their early 20's is more likely suffering from one of the shock absorbers, called the meniscus, being damaged by an impact or a twist in which the cartilage is directly torn, as opposed to slowly wearing away.
If you're suffering from the former, the degenerative type of cartilage problem, and the clicks and clunks are happening, my advice is to strengthen the knee muscles, your quads and hamstrings, as much as possible.
The stronger that those muscles are the more likely your knee will work in the correct position and the less likely that you'll get the sounds.
Crucially you'll be reducing the risk of the sand paper effect and the pain that awaits.