For two years prior to this fast I suffered from mild pain in my left knee which made it very difficult to get up from the floor or run for more than a few minutes. Two weeks into the fast, that knee began to hurt like crazy. By day 16 I was unable to bend it. But that was somewhat expected. Many peopl who undertake a prolonged fast report what is referred to as a "healing crisis"- when the body is in a state of self healing during which pre-existing symptoms flare up as the body works to get rid of them.
Who knows what I had in my knee. Gout, pre arthritis, some nasty build up of fluids... Either way, it's all gone. After 3 days of being unable to stand or even slightly bend that knee - it all disappeared. I woke up on day 19 and it was as if I had a new knee. All symptoms are gone since then and I have resumed my hiking and biking activities and am glad I let it heal itself.
And to answer your other question, at 5'9 I weighted 182 at the beginning of the fast and 147 on day 23. I wasn't terribly overweight, and now at my ideal weight.
And day 21 is far from being at the point of true starvation. That doesn't normally happen until at least day 45.