The Ankle Radiograph

Anatomy

First, we’ll refresh our bony anatomy to contextualize the radiographic images. The ankle is composed of the distal tibia and fibula and the superior talus, which is stabilized by several ligaments and the fibrous syndesmosis.

Image source: Sports Medicine for the Emergency Physician A Practical Handbook

The standard ankle radiographic series consists of the AP, mortise and lateral views.

The AP View

Evaluates the ankle mortise, lateral process of the talus and soft tissue edema adjacent to the malleoli
Image is obtained with the foot in dorsiflexion
The adequate AP view should have:
- Distal tibiofibular overlap (normal is >6 mm)
- The lateral and medial malleoli in view
- Tibiotalar joint space open, but the mortise is not completely visualized
  - If the mortise if completely visualized then it is an AP mortise view

The Mortise View

Evaluates the ankle mortise, which is made up by the articulation of the tibia and two malleoli with the talar dome
Image is obtained with the leg in internal rotation at 15-20 degrees with the foot in slight dorsiflexion
Normal findings:
- Joint space width is uniform and measures 4 mm throughout
- Assessing the talus:
  - Surface of the talar dome is smooth without irregularities
  - Medial and lateral tubercles of the talus are intact
- Assessing the tibiofibular interosseous membrane
  - Tibia and fibula overlap to some degree
    - Separation here suggests a torn interosseous membrane
  - The space between the distal fibula and tibia at 1-cm proximal to the tibial articular surface should measure ≤ 6mm
    - Measurements > 6mm suggest a torn interosseous membrane

Source: Accident and Emergency Radiology: A Survival Guide

The Lateral View

Evaluates for fractures, dislocations, joint effusions and calcaneal fractures
Image is obtained with the patient in a lateral decubitus position and foot in dorsiflexion
Normal findings:
- The lateral malleolus is superimposed on the medial malleolus and extends more inferiorly than the medial malleolus
- The posterior tubercle (posterior malleolus) of the tibia is visualized
- The calcaneum is demonstrated and used to measure Bohler’s angle (normal >30°)
  - A reduced Bohler’s angle suggests a calcaneal fracture
- Base of the 5th metatarsal is included

Image source: Accident and Emergency Radiology: A Survival Guide

References

Davenport M, Galasso MM. Ankle. In: Sherman SC. eds. Simon’s Emergency Orthopedics, 8e. McGraw Hill; 2019. Accessed January 04, 2023. https://accessemergencymedicine-mhmedical-com.eresources.mssm.edu/content.aspx?bookid=2455&sectionid=193455124

Feger J, Knipe H, El-Feky M, Tibiofibular overlap. Reference article, Radiopaedia.org (Accessed on 04 Jan 2023) https://doi.org/10.53347/rID-77885

Gorton S, Jones J, Bell D, et al. Ankle (AP view). Reference article, Radiopaedia.org (Accessed on 04 Jan 2023) https://doi.org/10.53347/rID-40728

Gorton S, Jones J, Bell D, et al. Ankle (mortise view). Reference article, Radiopaedia.org (Accessed on 04 Jan 2023) https://doi.org/10.53347/rID-40730

Gorton S, Bell D, Er A, et al. Ankle (lateral view). Reference article, Radiopaedia.org (Accessed on 04 Jan 2023) https://doi.org/10.53347/rID-40861

Patel P, Russell TG. Ankle Radiographic Evaluation. [Updated 2022 Apr 28]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK557462/

Raby Nigel, Berman L, Morley S, de Lacey G. Ankle & Hindfoot. Accident and Emergency Radiology: A Survival Guide,3e. Saunders Ltd; 2015. Accessed January 04, 2023.

Sports Medicine for the Emergency Physician A Practical Handbook, pp. 242 – 272 DOI: https://doi.org/10.1017/CBO9781316084328.008[Opens in a new window]. Publisher: Cambridge University Press. Print publication year: 2016