What happens to you when you have had all of your knee cartilage removed?

Osteoarthritis. When cartilage is removed you are bone on bone which is painful and will eventually need joint replacement.
Bad things. It is exceedingly unlikely that all of the cartilage would be removed. Nothing good comes from having all the cartilage removed from a joint. Unfortunately when joints degenerate the cartilage surfaces can just fall off and then become a source of continued locking and joint irritation. If conservative treatment fails and symptoms are severe enough joint replacement is the only option.