AP Weight-Bearing Ankle is a radiography positioning projection of the Lower Extremity. Upright on a low platform, heels against the IR, toes forward. SID 40". The centering point is located center of the IR, both ankles included, heels against the IR. The central ray is perpendicular to the center of the IR, with both ankles standing. Image-quality criteria include both ankles symmetrically positioned and centered on IR, medial mortise open, lateral mortise closed; tibia and talus partly over the distal fibula. A sample technique is 70 kVp with DR 1.8 or CR 3.2 mAs, at an SID of 40 inches (102 cm).
Anatomy demonstrated
- Both ankle joints.
- Distal tibia and fibula.
- Medial mortise open.
Patient preparation
- Verify patient identity using two identifiers.
- Remove shoes and any radiopaque items from the foot and ankle.
- Have patient stand upright on both feet on a low platform, with proper support. Never stand the patient on the radiographic table.
- Heels back against the IR, toes pointing straight ahead toward the tube.
Position & centering point
Center of the IR, both ankles included, heels against the IR.
Central ray
Perpendicular to the center of the IR, with both ankles standing.
Exposure / technique
- kVp
- 70
- mAs
- DR 1.8 / CR 3.2
- SID
- 40" (102 cm)
- Notes
- Shows ankle joint space narrowing and the distal tibia-fibula relationship under weight. Merrill's weight-bearing section prints no SID or technique; this borrows its general chart's tabletop Ankle AP row. Sample technique: DR 1.8 / CR 3.2 mAs at 70 kVp, 40 in SID, for an 11 cm part. Adjust for your equipment.
kVp and mAs are sample values. Use caution when applying them in your department.
Image-quality criteria
- Both ankles symmetrically positioned and centered on IR.
- Medial mortise open, lateral mortise closed; tibia and talus partly over the distal fibula.
- Both ankle joints and the distal tibia and fibula included.
- Collimation: 1 inch outside the feet, 8 inches vertically to include the heel (Merrill's).
Common errors
- 1 Heels not pushed back against the IR.
- 2 Toes not pointing straight ahead toward the tube.
- 3 Both ankles not centered on the image.
Clinical indications
- Ankle joint space narrowing under weight-bearing, with side-to-side comparison.