The purpose of this case report is to describe a physical therapy approach designed to reduce the mechanical pressure at the site of a diabetic plantar ulcer. The patient was a 69-year-old man with diabetes mellitus of 24 years, insensitive feet, and a right plantar ulcer at the first metatarsal head for 21 months. He had a fixed equinus and rear-foot varus deformity, which seemed to place increased pressure in his forefoot. The patient was treated with total contact and showed progressive healing until he refused additional casting. One week later, the ulcer was considerably larger. He consented to resume cating, and the ulcer was completely healed in 85 days from the initial treatment. We provided the patient with extra-depth shoes with rigid rockerbottom soles and a polyethylene-lined ankle-foot orthosis. The ulcer remained healed at one-week and six-month follow-up visits. The primary cause of diabetic plantar ulcer is often excessive pressure on an insensitive foot, and physical therapists should utilize biomechanical principles to reduce these excessive plantar pressures.