The various causes of leg pain are atherosclerosis, deep vein thrombosis - leg pain
on walking (A blood
clot in a deep vein), Leriche syndrome (block in abdominal aorta and/or main leg artery), limb ischaemia (low oxygen to limbs), sciatica, spondylitis of lower vertebrae and peripheral vascular disease (arteries of limbs are involved). Your doctor did the right thing in doing Doppler tests. This, rules out the possibility of involvement of an artery or vein.