Knee click when doing bicycle crunches?

Something I noticed in my Workout today was my knee kept clicking every time I did bicycle crunches - is that anything to be concerned about?

It wasn't painful, though it did feel unpleasant. I know Kelli and Daniel always say clicking joints aren't a concern if they're not painful, but given how careful we have to be with knees I was wondering if they're an exception? Anyone know what I should be doing?

On the plus side, FB Bodyweight Week 2 Complete! 😀 loving this program so far!

Thanks 💙