At the time of my "dead" legs, I was deep into the clinical depression but in major denial over it. So I didn't have any of the meds yet to straighten the brain out. As a note, I had next to no energy at all, it just seemed that the weakness in my legs whenever I walked was the most taxing. The way I see it, the signals to my legs were out of whack and wasn't telling the legs to function the way I needed them to. So they were heavy and almost like dead weights. Slow, weak plodding along as I had to mentally work each step and make sure the foot and leg were stable before taking the next step with the other foot. Once the meds started to get into the system, my strength VERY slowly returned.
However, your concern about diabetes is one I also have. The circulation in my legs improves when on low-carb diets, making them stronger and warmer. I also deal with lymphedema in my legs which is also a circulatory problem and makes my legs weak. But this weakness is quite different from the weakness from the clinical depression. Diabetes is scary stuff - All these Christmas snacks aren't doing me any good right now. Let's get the sugar out of our systems and see how we both feel.