Diabetic Ulcers - Note that most of these ulcers occur in areas nourished by the medial branch of the posterior tibial artery.  It is the medial branch of the posterior tibial artery that is most susceptible to entrapment when the foot rolls inward and downward (abnormally pronates).  Abnormal pronation, if severe enough, can compress the medial branch against the suscentaculum tali.