On the swollen knee thing, that is something I actively manage to avoid on this group ride.
For this ride, I took a number of conditioning rides earlier this summer. Those proved to me that my aging self needs more time to bring up the fitness level to do longer rides at speed. A smallish hit to the ego and took some ribbing from my friends for taking the shorter route, but yeah, sometimes better to finish w/out taking the sag wagon, be last, and still be able to walk around like a normal person that night than having knee issues for a long time after.
That bit of wisdom I extrapolated/learned from a friend who once road his bike across the USA. After that success, he sort of got out of the bike riding habit, and 5 yrs later decided to do a double century with minimal preparation. Knees blew up like the aforementioned watermelons. They didn't go down very quick, and after 2 months, now just the size of volleyballs, went to get them drained. Following the the procedure, he got bactemia that really jacked him up (likely from germs on the skin that made into the
capsule from the drainage needle or he just waited too long with fluid where it shouldn't be or he didn't stay on the post op meds long enough or wasn't careful with the post op skin care at the needle sites).