Cocker Spaniel Pup/3 months

Question
My cocker spaniel started limping yesterday for no apparent reason. She does not express any pain when her rear legs are pulled, so I am at a loss as to why she is limping. She still plays w/the children, but isn't as active as she has been in the past. She normally can stand on her two hind legs for treats, etc and since yesterday she has not attempted to stand on her hind legs. Any advice, etc.

Answer
At her age she may well have just taken a tumble and hurt herself.
So don't panic :) and try to keep her as quiet as possible for a couple of days.  If she's eating and still reasonably active but just avoiding certain "positions" then I'd strongly suspect she's bruised herself.

My own boy, as a puppy, took a fall off a kitchen chair - seemed fine - I checked him over but the next day was limping.  So take her hind leg and just gently feel it all over and gradually put more gentle pressure on it and see if you can find out precisely where it's hurting.  If you don't see improvement within a few days then I'd take her to the vet.
Delores