I experienced incontinence as well for about 3 months after my total knee replacement and nerve block. It gradually got better and I am back to normal now. I also experienced a numb foot on the surgery leg and that is still the same 17 weeks later.
Ten months prior to my TKR, I had a total hip replacement and was incontinent for a while after that. There was no nerve block for that one. However, I was prepared and bought a big box of Depends before the knee replacement. I am happy to hear that I was not the only one.
The opioid I had was Hydromorphone which made me very thirsty and the walker didn't take me to the bathroom fast enough. As you get stronger your pelvic floor muscles will improve.
Once you can walk on your own, things really improve. Hang in there!