Bimalleolar Ankle Fracture: Causes, Surgery, and Recovery After Breaking Both Ankle Bones

Medically reviewed by Dr. Tom Biernacki, DPM — Board-Certified Podiatric Surgeon — Balance Foot & Ankle, Howell & Bloomfield Township, MI. Last updated April 2026.

What Is a Bimalleolar Ankle Fracture?

The ankle mortise—the socket that cradles the talus—is formed by three bony structures: the medial malleolus (inner ankle bump, part of the tibia), the lateral malleolus (outer ankle bump, the end of the fibula), and the posterior malleolus (the back edge of the distal tibia). A bimalleolar ankle fracture involves fractures of both the medial and lateral malleoli simultaneously. When the posterior malleolus is also fractured, the injury is termed a trimalleolar fracture. These combined fractures produce significant ankle instability because multiple bony and ligamentous stabilizers are disrupted, typically resulting in the talus shifting out of the ankle mortise.

Mechanism of Injury

Bimalleolar fractures most commonly result from rotational forces applied to the ankle—twisting falls, sports injuries, and motor vehicle accidents are the most common mechanisms. The Lauge-Hansen classification system describes four distinct fracture patterns based on foot position at the time of injury (supinated or pronated) and direction of deforming force (adduction, external rotation, or abduction). Understanding the fracture pattern helps surgeons predict associated ligamentous injuries and plan surgical fixation.

Diagnosis

Standard three-view ankle X-rays (AP, lateral, and mortise views) identify the fracture pattern, assess displacement of the malleoli, and evaluate the width of the medial clear space (widening indicates deltoid ligament disruption or medial malleolus fracture). CT scan is obtained when posterior malleolus fracture size is uncertain or complex fracture patterns require more detailed planning. MRI may identify syndesmotic ligament injuries that are not apparent on X-ray.

Surgical Treatment: ORIF

Surgical open reduction and internal fixation (ORIF) is indicated for the majority of displaced bimalleolar fractures to restore anatomic alignment of the ankle mortise, which is essential for long-term ankle joint health and function. Surgery is typically performed 5–14 days after injury, after soft tissue swelling has partially resolved to reduce wound complication risk.

The fibula is typically fixed first through a lateral incision, using a precontoured lateral fibular plate and screws to restore fibular length, rotation, and alignment. The medial malleolus is then reduced and secured through a medial incision using one or two partially threaded cancellous screws or a tension band wire construct. The syndesmosis (the fibrous joint between the tibia and fibula above the ankle) is assessed by intraoperative stress testing; if disrupted, it is stabilized with one or two transcortical screws or newer suture-button devices that allow controlled syndesmotic motion.

Recovery and Rehabilitation

Patients are typically non-weight-bearing for 6 weeks postoperatively to protect the fracture fixation during initial bone healing. Progressive weight-bearing in a walking boot begins at 6 weeks with X-ray confirmation of healing. Transition to supportive footwear and physical therapy at 8–10 weeks. Physical therapy focuses on restoring ankle range of motion (dorsiflexion is typically most limited), strength, proprioception, and gait normalization. Return to light activity at 3–4 months; sports and physically demanding work at 6–9 months. Most patients achieve good functional outcomes, though some residual stiffness and weather-related aching is common. Post-traumatic ankle arthritis is possible over the long term, particularly with fractures involving significant articular surface damage.

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Ankle Fracture Surgery in Michigan

Bimalleolar ankle fractures — involving both the inner and outer ankle bones — typically require surgical fixation to restore joint alignment and prevent arthritis. Dr. Tom Biernacki performs expert ORIF (open reduction internal fixation) ankle fracture repair at Balance Foot & Ankle.

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Clinical References

1. Donken CC, et al. “Surgical versus conservative interventions for treating ankle fractures in adults.” Cochrane Database Syst Rev. 2012;(8):CD008470.
2. Egol KA, et al. “Ankle fractures: a practical approach to treatment.” AAOS Instructional Course Lectures. 2008;57:23-39.
3. Michelson JD. “Fractures about the ankle.” J Bone Joint Surg Am. 1995;77(1):142-152.

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