All in I was off work for about three months from the Opp to the return of my medical certificate.
Its important to get the knee moving ASAP so if you can get yourself into a hydrotherapy pool it will make recovery less arduous.
I also had an American licence and was advised to carry a letter stating that I had been prescribed morphine based drugs under medical supervision in case I got drug tested by the FAA. Apparently evidence of these drugs hangs about in the body for quite sometime.