Diabetic polyneuropathy (DN) is one of the most severe complications of diabetes. It is yet uncertain why patients either suffer from painful (PDN) or painless (NPDN) diabetic polyneuropathy. We prospectively performed magnetic resonance neurography of the sciatic nerve in 120 patients suffering from DN of varying severity and correlated the results with clinical symptoms and electrophysiological data. We found a higher load of lesions to the sciatic nerve in PDN compared to PDN (p<0.0001), extending over longer distances (p<0.0001). This indicates that proximal nerve damage is one of the main contributors to the development of PDN.