Knee pain

Sounds like a classic torn cartilage to me. The ring like buffer called the miniscus probably has a small tear in it and this interfers with the joint movement causing pain and often swelling (self protection). The tear means there is less buffer area and so there is more chance of bone to bone contact resulting in the clicks and grinding.
Get it x-rayed and MRI scanned to be certain and then keyhole surgery will most likely be suggested. You are presumably a young person and will be in almost perfect shape afterwards.
I had a similar op. a couple of weeks ago and whilst the pain and swelling has gone I doubt I will be leaping around again as I am in my 60s and there is some degeneration of the cartilage in general. This shouldn't apply to you.
By the way my damage was almost certainly caused by deep squats doing Tai Chi .... there's a lesson there for us somewhere 🙂
Best of luck,
M

Hi Muntjack, thank you for replying and for your advice. My knees a lot better since I have stopped doing the squats, but I still get some pain, sometimes.

Thanks again.

I am actually having the same problem. My right knee is killing me and I just stopped going to the gym waiting the pain will go away. I it's pretty common injury from doing squats. The thing is I am using ankle weights and cycling so I don't know what is the exact problem. Right now I just decided not to do anything and maybe then give up the squats and ankle weights.

doesnt sound like catalidge to me, more likely tension caused by quadriceps tightness, do you do any antagonist exercise to work hamstrings, this will maintain balance of muscles, the grinding will usually occur due to the patela being misplaced due to the tighness of quads, try researcing patella pain syndrome or corrective exercises,
regards
Gaz