I'm sorry your Dad is having a rough time and I'm glad that he has already seen his Doctor. I am also on Avandia and my main side affect has been weight gain and fluid retention. I don't mean to rag on medical docs, but so many will automatically diagnose back pain as a pulled muscle...been there done that! Does he have an Endocrinologist? The back pain "Could" come from so many sources, but with diabetes everything seems so much more complicated...lucky us
LOL. My mind automatically goes to nerve damage as that has happened to me. I have had lower back pain off and on for years but for the past few, the pain going down my legs has worsened. When the Endo did a nerve conduction test, my right lower back seems to be all messed up....and I mostly have pain on the left...go figure. Seeing the neurologist next month. Hopefully your Dad will just have a plain old pulled muscle, I will keep my fingers crossed for him.