3.2 yr old dd's knee is clicking

[steviesotherhalf]

I've only just noticed today that her left knee is clicking when she bends it. Never heard it do it before. I find myself worrying about everything sometimes and I just wondered whether this is normal from time to time. She isn't complaining that it hurts or anything. I know dc at this age have very 'soft' joints, but is this normal?

Any ideas or experience yourselves? Thanks.