Gyps back legs are cramping/shaky/stoved up?!?

Just yesterday I noticed when pulling up to my pens that my gyp was walking around stretching her back legs out. I opened the door to let her run thinking her legs maybe fell asleep and all she did was walk out. This gyp is 100 mph all day! She went and ate some grass for a few and I called her up and she seemed to walk fine. Again she's not running around at this point. I searched over her pads for anything. Pads were in good cond. rubbed her down stretching her legs and all. I pulled a tick off her chest no biggie. Thinking hey maybe that joker bit into a nerve. Again she acts like her legs are cramping and maybe her rear end is shaky. She a has a pump handle tail that goes 100 mph as well but it seem more shaky than normal. Also I had to buy an emergency bag of pedigree from Walmart this past Sunday. All it did was make all their number 2 run. Maybe it threw her system off. She just healed up from a decent from shoulder cut but she was on keflex and a topical ointment from the first night. I doubt there is any internal infection. The shoulder is a slight swollen but she did get rocked hard that night. Throwing this out there if anyone has had this problem or situation. Thanks JD