247 patients with a Weber type B1 malleolar fracture were randomized to immobilization for either 3 weeks in an orthosis, 3 weeks in a cast, or 6 weeks in a cast. The purpose of this study was to determine whether 3-week immobilization led to noninferior functional outcome over 52-week follow-up when compared to 6-week immobilization. Primary analysis suggested noninferiority of both 3-week immobilization protocols compared to the 6-week protocol with respect to Olerud-Molander Ankle Score after 52 weeks. In additional, all other secondary outcome measures of patient reported pain, function, and quality of life demonstrated no significant between group differences. The only significant difference noted between groups at 52 weeks was a higher range of plantar flexion in the 3-week orthosis group versus the 6-week cast group. Rate of nonunion did not significantly differ between groups.