Lateral Leg (Tibia & Fibula) is a radiography positioning projection of the Lower Extremity. Supine, turn toward affected side, knee and ankle flexed 45 degrees. SID 40". The centering point is located mid-point between knee and ankle joints on the ir.. The central ray is perpendicular to mid-leg in lateral position.. Image-quality criteria include tibia and fibula superimposed in true lateral position., knee joint space open showing anterior and posterior joint compartments.. Standard exposure ranges from 60 to 70 kVp, 4 to 7 mAs, at an SID of 40 inches (102 cm).
Anatomy demonstrated
- Distal femur and proximal tibia superimposed at knee.
- Entire tibia and fibula in superimposition.
- Knee joint space with condyles visible.
- Distal tibia and fibula in lateral relationship.
- Ankle joint in lateral position.
- Talus visible behind tibia.
Patient preparation
- Verify patient identity using two identifiers.
- Remove shoes and any radiopaque items from the leg.
- Position patient supine, turn toward affected leg side.
- Flex knee 45 degrees and place on IR in true lateral position.
- Flex ankle 45 degrees to match knee flexion angle.
Position & centering point
Mid-point between knee and ankle joints on the IR.
Central ray
Perpendicular to mid-leg in lateral position.
Exposure / technique
- kVp
- 60–70
- mAs
- 4–7
- SID
- 40" (102 cm)
- Notes
- Lateral positioning requires patient flexion at knee and ankle.
Image-quality criteria
- Tibia and fibula superimposed in true lateral position.
- Knee joint space open showing anterior and posterior joint compartments.
- Ankle joint space open and clearly visualized in lateral position.
- Interosseous space between tibia and fibula not visualized.
- Both knee and ankle clearly included on IR.
- Collimation 1.5 inches anterior and posterior, 1.5 inches above and below.
Common errors / ARRT traps
- 1 Insufficient knee flexion rotates proximal tibia.
- 2 Ankle too plantarflexed or dorsiflexed distorts distal view.
- 3 Leg not in true lateral but slightly rotated medially or laterally.
- 4 Off-centered CR omits knee or ankle joint.
Clinical indications
- Tibia or fibula fracture evaluation in lateral plane.
- Assessment of anterior or posterior knee subluxation.
- Suspected soft tissue or ligamentous injury.
- Post-operative evaluation of leg fixation in lateral view.
Aligned to the 2025 ARRT Content Specifications.