Motor neuropathy is less frequent. It can cause weakness of the small muscles that maintain normal foot shape resulting in a change to foot shape. The foot may develop a high arched shape with clawing of the toes (Pes cavus). A foot with Pes cavus is characterised by a high arch and retracted toes. The change of shape in the foot results in increased pressure on the metatarsal heads in the forefoot, this can lead to an excessive build up of callus, resulting in the tissues breaking down and an ulcer developing.