Thanks.... I was suspecting she stepped on something, but mom said she looked the cow over and didn't see any swelling or foreign objects (the cow is relatively tame), so I figure outside of footrot and foreign objects the next option would be a pinched nerve? I've only seen heavy breds a little stiff and uncomfortable, not lame, so I wasn't sure how severe it could be. I'm not home, so mom's going on the assumption it's footrot and soaking her hoof in epsom salts for the weekend, and if she's not better by Monday she goes to the vet.
FWIW, she's a 9 y/o Holstein cow and the leg she's lame on is the same one she had a severe case of footrot in 4 years ago. She's been sound up until now however.
Any other thoughts would be appreciated.