186 patients with a severe lateral ankle sprain (type III) were randomized to treatment to 3 weeks of rigid immobilization with a walking boot followed by 3 weeks of immobilization with a functional brace, or to a functional brace for 6 weeks. The purpose was to compare these two conservative treatment methods for outcomes in pain, function, and ankle stability up to 12 weeks after the injury. AOFAS scores were better for the first 6 weeks in patients receiving the functional brace, and pain and comfort outcomes also benefited within the first few weeks from using a functional brace. By 12 weeks, ankle stability was re-established effectively and similarly between the two groups.