Associations between fracture patterns are important and can ensure proper diagnosis and guide treatment. Occult posterior malleolus fractures associated with distal spiral tibia fractures often are underrecognized and the morbidity of a missed posterior malleolus injury can be substantial. We determined the association between the two injuries and evaluated the ability of a new protocol to improve management of these associated fractures. Of 62 consecutive patients with fractures of the distal third of the tibia, we retrospectively evaluated the first 39 patients and prospectively used a diagnostic protocol including computed tomography of the ankle in the subsequent 23 patients. The minimum followup was 3 months (mean, 25 months; range, 3–68 months). Twenty-four patients (39%) had fractures of the posterior malleolus. Before initiation of the protocol, intraarticular fractures were recognized in 33% (with one delayed diagnosis and one missed diagnosis), and after institution of the protocol, the detection rate was 48% with no known missed injuries and complete followup; however, with the limited power the detection rates were similar without and with the protocol. A spiral distal tibial shaft fracture with a proximal fibula fracture should alert the surgeon to investigate an occult ankle injury, particularly of the posterior malleolus. A protocol including computed tomography of the ankle may detect more injuries in a larger study.