walking sideways

Question
Our 4 year old Cocker has started twisting her hind end around when she walks, not all of the time and doesn't seem to be in any pain.
Most of the time she walks fine she is very active and loves to go outside, I've checked her paws for foreign objects and there are none.
It is pronounced when she walks this way, any suggestions?

Answer
Do you know when she does this?  For instance, after eating? After exercise?  In the morning?  Is she avoiding jumping?

How long has she been doing this?  Appetite?  

I'd check her all over by gentle but increasing pressure on her back and legs.  Bend her legs at the "knee" too. Go slow - start with an almost massage like pressure and gradually increase to see if there's an area that reacts.
Delores