popping sound

I started working out at a gym for the first time in my life and I was warming up doing the leg press.  Sadly as it is i was leg pressing 90+ pounds and there was a popping noise coming from both my knees.  Any idea what this would be?

I have about 6 ideas which come directly to mind but even if I were a doctor, its not really cool for me to try to diagnose you over a forum and I am not to be diagnosing at all, no med degree......teehee.
Here are some ideas I can throw out your way, I would need to see your knees and their rom and see the move which is causing this, watchyou do it but form is one question, tight ligamints like the lateral or medial collateral......patellar tendon tracking issues, hamstring and ham attachment issues......could be a number of things.
Linda

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