Forearm Lateral is a radiography positioning projection of the Upper Extremity. Seated, forearm lateral on IR with thumb up. SID 40". The centering point is located at the midpoint of the forearm, approximately 1 inch proximal to the elbow joint, in the lateral position.. The central ray is perpendicular to ir at the midpoint of the forearm, 1 inch proximal to the elbow joint.. Image-quality criteria include entire radius and ulna visible in true lateral position., radius and ulna superimposed in posterior aspect only.. Standard exposure ranges from 60 to 70 kVp, 2 to 4 mAs, at an SID of 40 inches (102 cm).
Anatomy demonstrated
- Entire radius in true lateral projection.
- Entire ulna from styloid to olecranon.
- Radial tuberosity visible and lateral.
- Radiocarpal joint at the wrist.
- Distal radioulnar joint articulation.
- Elbow joint in true lateral position.
Patient preparation
- Verify patient identity using two identifiers.
- Remove watches, bracelets, and radiopaque items from the arm.
- Seat the patient at the end of the table.
- Place forearm on the IR in lateral position with thumb up.
- Adjust table so humerus, elbow, and forearm rest in the same plane.
Position & centering point
At the midpoint of the forearm, approximately 1 inch proximal to the elbow joint, in the lateral position.
Central ray
Perpendicular to IR at the midpoint of the forearm, 1 inch proximal to the elbow joint.
Exposure / technique
- kVp
- 60–70
- mAs
- 2–4
- SID
- 40" (102 cm)
- Notes
- Tabletop technique. Include both wrist and elbow joints.
Image-quality criteria
- Entire radius and ulna visible in true lateral position.
- Radius and ulna superimposed in posterior aspect only.
- Wrist and elbow joints included and open.
- Radial tuberosity facing lateral and visible.
- Bone trabeculae sharp, no motion blur.
- Collimation: 1 inch on all sides of the forearm.
Common errors / ARRT traps
- 1 Pronation or supination rotates the radius off true lateral.
- 2 Lifting the shoulder closes the elbow joint.
- 3 Off-center CR clips the wrist or distal humerus.
- 4 Shifting the forearm forward or backward changes the alignment.
Clinical indications
- Suspected radius or ulna fracture in lateral plane.
- Forearm trauma assessment when AP is inconclusive.
- Post-operative follow-up of forearm fracture fixation.
- Elbow effusion or fat pad evaluation.
Aligned to the 2025 ARRT Content Specifications.