AP Medial Oblique Mortise Ankle is a radiography positioning projection of the Lower Extremity. Supine, leg internally rotated 15-20°. Talus between malleoli. SID 40". The centering point is located midway between the malleoli. leg internally rotated 15-20 degrees so intermalleolar line is parallel to ir.. The central ray is perpendicular to the ankle joint.. Image-quality criteria include talus centered between medial and lateral malleoli., medial and lateral malleoli symmetric in their relationship to talus.. Standard exposure ranges from 60 to 70 kVp, 4 to 7 mAs, at an SID of 40 inches (102 cm).
Anatomy demonstrated
- Medial malleolus in direct profile.
- Lateral malleolus in direct profile.
- Talus centered in mortise between malleoli.
- Syndesmotic space between tibia and fibula.
- Distal tibia and fibula.
- Tibiotalar articulation.
Patient preparation
- Verify patient identity using two identifiers.
- Remove shoes and any radiopaque items from the foot and ankle.
- Position patient supine with ankle extended on the IR.
- Internally rotate the entire leg 15-20 degrees so intermalleolar line is parallel to IR.
- Ensure full ankle extension and proper rotation.
Position & centering point
Midway between the malleoli. Leg internally rotated 15-20 degrees so intermalleolar line is parallel to IR.
Central ray
Perpendicular to the ankle joint.
Exposure / technique
- kVp
- 60–70
- mAs
- 4–7
- SID
- 40" (102 cm)
- Notes
- Mortise view shows talus centered between medial and lateral malleoli.
Image-quality criteria
- Talus centered between medial and lateral malleoli.
- Medial and lateral malleoli symmetric in their relationship to talus.
- Tibiotalar joint space open and uniform width bilaterally.
- Distal tibia, fibula, and talus all clearly visible.
- Syndesmotic space visible between distal tibia and fibula.
- Collimation 1 inch on sides, 1.5 inches beyond ankle.
Common errors / ARRT traps
- 1 Insufficient rotation fails to center talus between malleoli.
- 2 Excessive rotation distorts the mortise relationship.
- 3 Off-centered CR clips the malleoli or talus.
- 4 Ankle plantarflexion or dorsiflexion alters the joint angle.
Clinical indications
- Ankle fracture evaluation, especially lateral malleolus or syndesmotic injury.
- Assessment of the ankle mortise integrity.
- Ligament injury evaluation with stress views.
- Post-operative hardware inspection and alignment check.
Aligned to the 2025 ARRT Content Specifications.