Friend, the history and symptoms that you are describing could be related to many different medical conditions. Common causes are: A soft tissue (muscle, tendon or ligament) injury, joint problems (OCD), panosteitis, etc. The fact that this involves both limbs, I would place panosteitis high on the list of possible causes. We really don't know why panosteitis happens but it has been associated with puppies that are growing to fast. To diagnose she would need xrays, but, I understand your financial limitations. This is what you can try:
1- It sounds like she has a very rich diet and this may contribute to panosteitis. I would recommend you change her diet to an adult dog food.
2- Rest her for the next couple of weeks, no running or jumping. Activity should be limited to urinate and defecate on a leash.
3- I would discuss with your vet about dispensing Rimadyl (anti inflammatory) to have at hand to be used as needed. If this is related to panosteitis dogs could experience these painful episodes until they are at least 2 years old.
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