Dr said no squats, what now?

So I've been having a lot of pain in my knees over the past year and a bit. Went to doc, got ultrasounds and xrays, nothing, so went for MRI. Turns out I've got fissures in the cartilage behind my patella, which gets pulled apart when I put load on my knees, even going up a set of stairs.

So doctor says no squats until we figure it out, but I don't want to do nothing, otherwise I'll lose all the strength in my legs. I'm thinking leg extensions and ham curls should still be okay, right? Any other recommendations? I can't do anything that'll put either leg under load, which is annoying, coz I'd just joined the double plate club and was on a roll.

Edit: not looking for treatment, my doctor is talking to a specialist atm.