Whats wrong with my doggie's back?

Today my doggie had been reluctant to run, climb, or jump and if you pick her up she yelps in pain. I noticed her food and water bowl had been untouched so I put it in a stool so that she didn't have to bend over to get to it and then she started eating but she won't eat it off the floor. She is a little 3 year old beagle. what could be wrong with her? it sounds like a back problem