Broken or injured leg?

Hi, I'm new here, btw... but I'll get straight to the point, perhaps trolling the forums a bit at a later time... :wink:

So, I woke up today, and, when I saw my rat, Bob, he seemed to have some trouble using his left back leg. He had trouble scratching himself or using it to move himself around. So I sort of put a splint on it, so it he wouldn't move around too much and make it worst. But, he's now lying on his back with his feet in the air, I don't think he likes it :?

Any tips, or information is appreciated!

-Moose