Elbow AP Oblique (Lateral Rotation) is a radiography positioning projection of the Upper Extremity. Arm extended, rotated 45 degrees laterally until 1st/2nd digits touch the table. The centering point is located mid-elbow joint with the arm rotated 45 degrees laterally from a true ap position.. The central ray is perpendicular to the mid-elbow joint.. Image-quality criteria include radial head, neck, and tuberosity free of superimposition by the ulna., capitulum visible in profile.. Standard exposure ranges from 60 to 75 kVp, 3 to 6 mAs, at an SID of 40 inches (102 cm).
Anatomy demonstrated
- Radial head, neck, and tuberosity.
- Capitulum of the humerus in profile.
- Proximal radioulnar joint space.
- Distal third of the humerus.
- Open humeroradial joint.
- Coronoid process partially seen.
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.
- Extend the arm over the IR, palm up, in true AP first.
- Rotate the entire arm 45 degrees laterally until 1st and 2nd digits touch the table.
Position & centering point
Mid-elbow joint with the arm rotated 45 degrees laterally from a true AP position.
Central ray
Perpendicular to the mid-elbow joint.
Exposure / technique
- kVp
- 60–75
- mAs
- 3–6
- SID
- 40" (102 cm)
- Notes
- Lateral rotation opens the proximal radioulnar space and frees the radial head.
Image-quality criteria
- Radial head, neck, and tuberosity free of superimposition by the ulna.
- Capitulum visible in profile.
- Open elbow joint space.
- Distal humerus and proximal forearm both included.
- Bone trabeculae sharp, no motion blur.
- Collimation: 3 inches proximal and distal to the joint.
Common errors / ARRT traps
- 1 Rotation under 45 degrees leaves the radius partially overlapping the ulna.
- 2 Rotation past 45 degrees foreshortens the radial head.
- 3 Failure to keep the digits touching the table tells you the rotation is short.
- 4 Lifting the shoulder closes the joint space.
Clinical indications
- Suspected radial head or radial neck fracture.
- Evaluation of the proximal radioulnar joint.
- Post-trauma assessment when AP shows overlap.
- Follow-up of radial head fixation.
Aligned to the 2025 ARRT Content Specifications.