Böhler Angle (Calcaneus)
Assesses the tuber joint angle of the calcaneus on a lateral foot radiograph to detect depression of the posterior facet in calcaneal fractures.
Böhler tuber joint angle is the classic radiographic measure of calcaneal height on the lateral projection. A normal calcaneus maintains a well-defined superior contour; when the posterior facet is depressed by an intra-articular fracture the angle flattens or reverses. It is a rapid, reproducible screening measurement that flags subtle fractures which might otherwise be missed.
🧮 Interactive Calculator
📐 Formula
Böhler angle = angle between (a) line from highest point of posterior facet to highest point of anterior process and (b) line from posterior facet to superior tuberosity.
When to Use
- Lateral foot or ankle radiograph after axial-loading trauma (fall from height, road traffic collision).
- Suspected calcaneal fracture where the fracture line is not obviously displaced.
- Follow-up assessment of reduction after operative fixation of a calcaneal fracture.
How It Works
- Draw a line from the highest point of the posterior articular facet to the highest point of the anterior process.
- Draw a second line from the highest point of the posterior facet to the most superior point of the calcaneal tuberosity.
- The angle subtended between the two lines is the Böhler angle.
- Compare with the contralateral side when the diagnosis is equivocal.
Interpreting the Result
- Normal Böhler angle is approximately 20–40°.
- An angle < 20° indicates loss of calcaneal height and is suggestive of a depressed intra-articular calcaneal fracture.
- A flattened or reversed (negative) angle indicates severe posterior facet depression.
- An angle > 40° is uncommon and may reflect measurement error or normal variant.
Limitations & Pitfalls
- Sensitive to projection and rotation; a mal-positioned lateral can falsely lower or raise the angle.
- A normal angle does not exclude a non-displaced or extra-articular fracture — CT remains the standard for surgical planning.
- Inter-observer variation exists in identifying the reference points.
References
- Böhler L. Diagnosis, pathology, and treatment of fractures of the os calcis. J Bone Joint Surg. 1931;13:75-89.
- Knight JR, Gross EA, Bradley GH, et al. Boehler’s angle and the critical angle of Gissane are of limited use in diagnosing calcaneus fractures in the ED. Am J Emerg Med. 2006;24(4):423-427.
⚕️ For clinical decision support only. Always verify calculations and apply clinical judgment.