As an Rn, i cannot medically diagnose a patient-thats a md's or DO's job-but i start my head to toe physical exam by asking if he has had bloodwork done...and if they are wnl's. then i would get an mri or ct of that leg.
i would consider that hes a diabetic that is untreated-is he overweight? does he exercise and eat a healthy diet?
are his renal and liver functions wnl? does he have a hx of hypertension? i would take him to get another opinion-if it is peripheral neuropathy they can help him with meds.
i have low potassium blood levels- and if i dont take in enough K+, i get muscle cramps and stinging in my legs.. is he on any meds that flush water out of his system? (like Lasix) they rob your body of potassium-causing muscle pain, eventually cardiac dyssrhythmias.
does he have any history of thrombus (bloodclots) in his legs? is just one leg swollen, and the other isnt? any signs of shortness of breath? that would be a clot in the leg-it can travel to the lungs. you said he hurt one leg, that makes me wonder if either there is a hairline fracture or a clot trapped in it.
it has to be either a CNS problem-(neuro) or physiologic problem-muscle, bloodflow, vasoconstriction of the peripheral vessels- or can be a chemical imbalance.
i tell you what, if you know any nurse practicioners, i would take him to one. they are worth their weight in gold.. and troubleshoot better most (not all lol) doctors ive ever worked with-then again i work with lazy, burnt out docs lol. dont take just one or two doctors answers... go see a few more. i wish you the best, and wish i could help, but to be able to even help i would have to talk to him, get a good history and do a physical exam.. then start troubleshooting from there..
please keep us up to date--- i know you can find the right answer!