Pure Ankle Dislocation: A Rare but Important Orthopedic Injury

Ankle injuries are among the most frequent orthopedic presentations in emergency departments worldwide. However, pure ankle dislocation—a complete dislocation of the tibiotalar joint without any associated fracture—is an extremely rare event. Despite the ankle’s robust ligamentous support and the bony stability of the ankle mortise, certain extreme mechanisms of injury can lead to this unusual condition.

What Is Pure Ankle Dislocation?

Unlike typical ankle dislocations that are accompanied by malleolar fractures, pure ankle dislocation occurs when the talus is displaced from its articulation with the tibia and fibula without breaking any surrounding bones. These cases are not only rare but often misdiagnosed due to their similarity to other hindfoot injuries and the lack of specific ICD coding.

How Rare Is It?

A large-scale systematic review and hospital data audit estimated that pure ankle dislocations account for:

• Only 0.065% of all ankle injuries
• And 0.46% of all ankle dislocations

At a tertiary referral hospital with a catchment population of over 1.3 million people, only 3 confirmed cases of pure ankle dislocation were recorded in a 12-year span. Even when including possible but unconfirmed cases, the incidence was still less than 1 in a million per year.

What Causes Pure Ankle Dislocation?

Most commonly, pure ankle dislocations result from high-energy trauma, such as:

• Motor vehicle accidents
• Falls from a height
• Sports injuries, especially football, basketball, or high-impact landings

The typical biomechanical mechanism involves a combination of:

• Axial loading (a downward force through the leg)
• Plantarflexion (pointing the foot downward)
• And either inversion or eversion (twisting of the ankle inward or outward)

These forces can rupture key ligaments around the ankle without fracturing the surrounding bones.

A Case Example

One recent case involved a 22-year-old male who suffered a closed pure ankle dislocation after falling from a stair step—just one meter in height. The injury resulted in posteromedial dislocation of the talus, and MRI later showed a rupture of multiple ligaments, including the anterior talofibular ligament (ATFL), calcaneofibular ligament (CFL), and partial tear of the deltoid ligament, along with a small osteochondral lesion.

How Is It Diagnosed?

Initial imaging involves plain radiographs (X-rays) in both anteroposterior and lateral views to confirm the dislocation and rule out fractures.

• CT scans post-reduction help detect hidden fractures or syndesmotic widening.
• MRI can reveal soft tissue damage including ligament tears and osteochondral lesions.

Neurovascular assessment is critical before and after reduction, as approximately 19% of cases involve temporary vascular compromise.

Direction of Dislocation

Among 154 reviewed cases, the posteromedial direction was the most common (46%), followed by:

• Posterior (15%)
• Medial (20%)
• Lateral (12%)
• Other types (anterior, superior, anterolateral) were far less frequent.

This directional variability is closely tied to the injury mechanism.

Classification System (Fernandes)

Fernandes proposed a classification based on direction and mechanism:

Type	Direction	Mechanism
I	Posteromedial/Medial	Axial loading, plantarflexion, internal rotation
II	Lateral	Axial loading, plantarflexion, external rotation
III	Superior	Axial loading, dorsiflexion, external rotation
IV	Anterior	Axial loading, plantarflexion, anterior force

Management and Treatment

Closed Injuries

Most closed pure ankle dislocations are treated non-operatively:

1. Immediate reduction under sedation
2. Short leg cast immobilization (typically 6 weeks)
3. Functional rehabilitation with focus on range-of-motion and peroneal strengthening

In the case described earlier, the patient began weight-bearing at 6 weeks and returned to full function by 12 months post-injury.

Open Injuries

These require more aggressive management:

• Wound debridement
• IV antibiotics
• Tetanus prophylaxis
• Possible primary or delayed ligament repair

Half of all reviewed pure dislocations were open injuries, and they showed higher complication rates—including infections (8%), stiffness (23%), and posttraumatic arthritis (14%).

Do Ligaments Need to Be Surgically Repaired?

One of the key takeaways from the literature is that surgical ligament repair does not significantly alter outcomes. In a large review, only 2.7% of patients had ankle instability after treatment—regardless of whether ligament repair was performed.

The consensus is that ligament repair should only be considered in cases of chronic instability, not as a routine primary intervention.

Outcomes and Prognosis

The outlook for patients is generally excellent:

• 59% of patients reported no symptoms after treatment
• 18% experienced ankle stiffness
• 10% developed arthritis
• Only 2.7% had lasting instability

Patients with closed injuries fare better than those with open dislocations. Additionally, early weight-bearing and shorter immobilization (2–3 weeks) may reduce stiffness without increasing instability.

Recommendations for Clinicians

For Closed Injuries:

• Immediate reduction
• Short leg cast (2–6 weeks)
• Begin functional rehab early

For Open Injuries:

• Emergency reduction
• Surgical debridement per Gustilo-Anderson classification
• Consider syndesmosis fixation if required
• Avoid unnecessary ligament repair unless instability persists

Conclusion

Pure ankle dislocation is a rare but significant orthopedic injury. Awareness of this condition is essential for prompt diagnosis and management. The evidence suggests that conservative treatment, when applied properly, leads to excellent functional outcomes in most cases—especially in closed injuries.

While surgery may be required in open injuries or cases of neurovascular compromise, routine ligament repair is generally unnecessary. Early recognition, appropriate imaging, and structured rehabilitation are the cornerstones of successful recovery.