Differentials
Lateral ankle ligament tear (anterior talofibular ligament and calcaneofibular ligament)
SIGNS / SYMPTOMS
Minimal lateral malleolar posterior bony tenderness. There may be a positive anterior drawer sign of the ankle or increased talar tilt depending on extent of the tear. Uncommonly there is significant deformity to the ankle.
INVESTIGATIONS
Plain x-rays will not identify a fracture.
MRI examination or musculoskeletal ultrasound may show oedema with or without a tear to the lateral ankle ligaments (anterior talofibular ligament and calcaneofibular ligament).
Achilles tendon rupture
SIGNS / SYMPTOMS
No malleolar tenderness. There may be a gap in the Achilles tendon and a positive Thompson's test.
INVESTIGATIONS
Plain x-rays demonstrate no fracture, and an MRI or musculoskeletal ultrasound of the Achilles tendon will demonstrate a tear.
Talar fracture
SIGNS / SYMPTOMS
There may be no malleolar tenderness. There may be a deformity to the ankle and hindfoot.
INVESTIGATIONS
Plain x-rays demonstrate a fracture of the talus.
Syndesmotic disruption
SIGNS / SYMPTOMS
There may be no malleolar tenderness. External rotation test and calf squeeze test may demonstrate pain in the syndesmosis.[38]
INVESTIGATIONS
Plain x-rays demonstrate no fracture but may show tibiofibular widening.
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