I get something like that when I am bleeding a lot for a long time. I've equated it with my anemic times. And, I've also read that RL can sometimes be associated with low iron. My doc just put me on iron supplements and my legs are normal again.
--40 year old female, dx as UC in '04 (1st symptoms in '03), switched to Crohn's in '05, 1 fistula, crohn's colitis, limited to large intestine
--rejected (reaction/didn't work): Asacol, AZA, 6-MP, MTX, Remicade, Humira, prednisone
--methylpred - finally off 6/15/08, tried Prochymal in Phase III study (can't wait til it's approved!)
--started Tysabri 3/21/08, started Xifanan 5/24/08
--single mom to 10-yr-old girl