RE: Dog limping, please help
I trust that your dog has been on a flea/tick medication.
However, it is still posible with any medication that a tick survives.
Rocky Mnt Spotted fever causes symtoms that you are describing.
No Defects and no obvious pain. just loss of control and soreness in the backend.
The treatment for this is Tetracycline 3x a day for 14 days
100 mg per 10lbs of body weight
I am not a vet and hopefully it is something simple.
I encourage you to seek a professional opoinon asap
Diagonis for this runs betwwen 150-350
blood work will have to be sent to a lab