Like BB I have had a TKR and thankfully seem to have had far less discomfort, I ditched the pain relief drugs quite quickly to the surprise of the medical staff but this probably reflects the pain levels prior to the procedure.
Getting the Knee moving ASAP is key to a good recovery and to this end hydrotherapy is very good as you can walk in the hydrotherapy pool in the normal way while your body weight is largely supported by the water.
My procedure was done twelve years back and I was back to flying with a class one medical after three months , my company wanted me to demonstrate controlling the aircraft at MTOW with an engine failure at V1 and then fly a visual circuit to a landing without using rudder trim as this covered the worst posable scenario they could think of. Once the CAA had the all clear they re-issued my medical.
It took about a year for me to get very nearly the full range of movement back in my Knee and it was about nine months before I could comfortably ride my motorcycle, that was all twelve years back and now the only drawback is I get the full search from security each time I go to work.