I don't think the line between sore and injured is really that black and white. He's old. His body is breaking down. He has to be paced for a 162 game season and likely pushed himself on the home-stand to try and get #600 there.
Would it accomplish anything to say that his legs are weak? Is that an injury? How about having your hamstrings bolted to your femur?
We also need to consider the newly reinforced limits thanks to HIPAA. Getting medical information is quite difficult, especially if there are no actual medical procedures being performed to treat it.
I don't mean to give Junior a free pass, but I think the idea that he's being held out for the purpose of hitting #600 at home a bit conspiracy theroyish and the insistence on getting a full description of his medical condition a bit presumptuous.