I have arthritic cartilage degeneration in both knees (especially the meniscus), although it's moderately worse in my right knee for reasons unknown. Over the last 2 years I've tried a few steroid injections and only had minor relief, so tried the still somewhat experimental PRP therapy (where they collect some blood and centrifuge it down, taking the platelet rich plasma fraction and injecting that into the knee to stimulate growth factors which supposedly reduce inflammation), which worked pretty well for 5-6 months but the pain has returned somewhat.
During this time I went for two rounds of PT and still do about 20 minutes of knee exercises every other day, mostly building strength in the quads, which has been shown to stave off the need for knee replacements. Having said all that, the pain isn't enough to keep me from playing sports and being active (4-5 rounds of disc golf a week and once weekly soccer, plus regular walks with my wife), so I'm not quite at the knee replacement stage, but I've been thinking about it, as I'd still rather be 100% than 85% and of the dozen or more people I know who've had them, they all swear by them. So it's interesting to read all the comments here.
With regard to surgery, I did have a full rotator cuff tear repaired about 10 years ago and the first 36 hours post-op was the worst pain I ever had (after the nerve block wore off), but after that, no issue for me. People would talk about how terrible the PT was and I never thought the PT was more than a mild annoyance - I was religious about going to PT and doing PT work at home and in about 3.5 months I was back to full activity. My PT guy is one of the best in the area (works with many RU athletes): Alex Ivashenko at Professional PT.