Possibly something wrong with cat? please help!?

I adopted a beautiful year old cat at the aspca the other day. I have a vet appointment scheduled for this coming weekend. I am extremely worried though because I feel there is something wrong with her. She walks "silly" with her back legs. Almost as though she has no balance. She is all wobbly. Now keep in mind, she was in a cage for 6 months of her life. Could her muscles be atrophied? I am so worried that it could be hip dysplasia. I do not know what I would do without her, I am already so so attached. Any advice on what it could be or if anyone has had similar problems with caged up shelter cats?