Yes, this can be caused by diabetes.
I developed a thigh pain last March that got worse and I ended up being unable to sleep due to cramps/aches in my legs (I'd wake up in agony, literally screaming in pain.) As soon as I got up and walked around the pains went away. (Gp said it was 'wear and tear') Spent a lot of time sitting downstairs in the early hours drinking tea and watching Star Trek on Netflix as I couldn't sleep.
Anyway, two weeks after diagnosis of T2D (August) and a low-carb diet the pain reduced dramatically (Pretty much went away) and I could sleep again (Six or so months without sleep probably did not help.). I did get a weird 'itching' on my legs when I sat down that slowly faded away over the following three to four months. I also had a lot of weird bone clicking and could see my muscles pulsing.
It's all gone now and I feel back to normal.
Not sure what was going on there (Proximal neuropathy sounds close, at least the thigh pain aspect ) but the GPs didn't seem interested and the Diabetic nurse just shrugged when I told her and said "It can happen." She did some checks and said I had a strong pulse in my feet ("They're in better condition than mine!"), but to tell them if it happened again.
The fact it went away so quickly as soon as I started low-carb does indicate that it was a consequence of high blood sugar.
How are you blood sugars?