So, I have no cartilige behind my knee cap

Guess it’s kind of important.

I wrecked myself marching in a long parade, and was just almost barely able to walk afterwards. Off to the doc. Xrays, lots of manipulation, cortisone and a huge brace. Instructions to ice it, which is weird since it happened about 2 weeks ago, but he says there’s fluid.
Long/short…I don’t need a replacement joint. They will be injecting fillers behind the knee caps for cushioning. Anyone else have this done?