So many ways knees can complain, and so many different approaches for
addressing the problems.
For me, I observe the following:
--------------------------------------------------------
Morning, just before ride: typical weight
Morning, day after ride: typical weight, maybe down one pound
Morning, two days after ride: weight up four to six POUNDS over the
previous day (*)
Morning, three days after ride: weight still up (*)
Morning, four days after ride: weight back to typical
--------------------------------------------------------
On these higher-weight days (*), my legs are tight and my knees may
hurt. It is a very "external" pain. Jeans fit more tightly. I am
clearly holding fluid (no way I've eaten that much weight in food, and
no way I've ingested 15,000 calories the day after a ride!) and a lot
of that fluid is pretty clearly in my legs. My uneducated assumption
is that my body is repairing, and using water to transport materials.
I'm just guessing, though.
(I believe I've heard Rob Hawks and Lisa-Susan McPhate talk about
similar post-ride weight swings.)
*If* I am good and do an easy recovery ride -- very gentle pedaling
for the better part of an hour -- it seems that I can often "flush"
some of this fluid sooner.
Going for a nice walk feels very good, too.
Also! Putting my legs up (lying on my back with my legs totally
vertical against a wall) any time after a ride -- immediately, next
day, etc., can help.
I now expect this whole process to happen, and don't fight it. Note
that descending stairs facing backwards, for me, can be done
pain-free. Also, ibuprofen can help, but I prefer to do the other
things -- recovery ride/walk, putting legs up, stretching, rollers,
and just taking it easy.
Good luck!
-Greg