Knee - AP

Radiographic Positioning

Adult

Other related pages of interest Applied Radiography Radiographic Anatomy Radiographic Protocols

Name of projection	Knee - AP
Area Covered	Distal femur, proximal tibia & fibula, patella, and knee joint.
Pathology shown	Any fractures, lesions, or bony changes secondary to degenerative joint disease.
Radiographic Anatomy	Knee Radiographic Anatomy
IR Size & Orientation	18 x 24cm Portrait
Film / Screen Combination	Detail (CR and DR as recommended by manufacturer)
Bucky / Grid	No
Filter	No
Exposure	60 kVp 8 mAs
FFD	100 cm
Central Ray	Directed parallel to the tibial plateau, approximately 1.5cm distal to apex of the patella Central ray angle 5° caudad for thinner leg 0° for normal leg 5° cephalad for thicker leg
Collimation	Centre: Shutter A: Open to film size superiorly and inferiorly Shutter B: Open to include lateral skin margins
Markers	Distal and Lateral Marker orientation AP
Shielding	Gonadal (check your department's policy guidelines)
Respiration	Not applicable
Positioning	Patient supine on the X-ray table Cushion for head Align and center leg and knee to CR and to midline of IR. Rotate leg internally 3° to 5° for true AP (or until interepicondylar line is parallel to plane of IR.) Place sandbags by foot and ankle to stabilise if needed.
Critique PACEMAN	Positioning No rotation will be evident by the symmetric appearance of the femoral and tibial condyles and the joint should be superimposed by the tibia. The intercondylar eminence will be seen in the center of the intercondylar fossa. Area Covered The distal femur and proximal tibia and fibula are shown. The femorotibial joint space should be open, with the articular facets of the tibia seen on end with only minimal surface area visualized. Collimation The collimation field should align with the long axis of the IR. The center of the collimation field should be to the midknee joint space. Exposure Optimal exposure will visualise the outline of the patella through the distal femur, and the fibular head and neck will not appear overexposed. No motion should exist; trabecular markings of all bones should be visible and appear sharp. Soft-tissue detail should be visible.
Special Notes