Abby is a Australian Shepherd/Labrador/Pittbull mix. She will be 7 years old this August. She weighs 42 pounds of solid muscle, and is very energetic when playing with the younger dog. Every now and then she limps. She never cries out in pain, and has no problem with me touching whatever leg she's favoring. This morning she was favoring her back right leg. I massaged her for a bit and she seemed to get a little better. Should I take this as a warning that she's developing an issue, or does it sound like she's just over exerting herself and getting aches and pains? I know I wake up kind of stiff in the mornings myself. I've heard of some people giving their dogs aspirin (or maybe ibprofren, not sure) sometimes for aches or stiff joints. Is this something I should be doing for her?