AP Distal Femur is a radiography positioning projection of the Lower Extremity. Supine, leg extended in true AP. Knee joint included. The centering point is located midway between hip and knee on the affected femur. knee joint must be on the ir.. The central ray is perpendicular to mid femur, centered to include the knee joint.. Image-quality criteria include distal two-thirds of femur including knee joint visible., femoral condyles symmetric with no rotation.. Standard exposure ranges from 70 to 80 kVp, 8 to 14 mAs, at an SID of 40 inches (102 cm).
Anatomy demonstrated
- Distal two-thirds of the femoral shaft.
- Medial and lateral femoral condyles.
- Patella over the distal femur.
- Knee joint space and tibial plateau.
- Trabecular pattern of the distal femur.
Patient preparation
- Verify patient identity using two identifiers.
- Remove radiopaque items from the leg.
- Position patient supine with leg fully extended.
- Leg in true AP with no rotation of the foot.
- Confirm pregnancy status when applicable.
Position & centering point
Midway between hip and knee on the affected femur. Knee joint must be on the IR.
Central ray
Perpendicular to mid femur, centered to include the knee joint.
Exposure / technique
- kVp
- 70–80
- mAs
- 8–14
- SID
- 40" (102 cm)
- Notes
- Grid required for adult femur. 14"x17" lengthwise IR.
Image-quality criteria
- Distal two-thirds of femur including knee joint visible.
- Femoral condyles symmetric with no rotation.
- Joint space between femur and tibia open and clear.
- Patella centered over the distal femur.
- Trabecular detail of distal femur visible.
Common errors / ARRT traps
- 1 Rotation of the leg distorts the femoral condyles.
- 2 Failure to include the knee joint on the receptor.
- 3 Off-center CR clips the distal femur.
- 4 Inadequate exposure obscures cortical detail.
Clinical indications
- Suspected distal femoral fracture or stress injury.
- Evaluation of femoral shaft pathology near the knee.
- Post-surgical follow-up of distal femur hardware.
- Assessment of bone lesions in the distal femur.
Aligned to the 2025 ARRT Content Specifications.