I had to have my kneecap removed back in 1979 after a previous surgeon had drilled holes into it to relieve pressure! Unfortunately the holes had all disintegrated into one large hole! The OS who did my tkr said that I was only the third person that he'd operated on that didn't have a kneecap and the the wouldn't be able to use a replacement, so no kneecap.
I still take meds although l had cut back last week before l had my fall. I take naproxen, paracetamol and codeine (15mg) - only take codeine when l need to.