Indications for imaging
Trauma, bone pain, arthritis, joint replacements, soft tissue
calcifications loose bodies, osteosarcoma, Bakers cyst (a collection of synovial fluid which has escaped from the knee joint or a bursa and formed a new synovial-lined sac in the popliteal space; seen in degenerative or other joint diseases.)
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Anatomy Demonstrated
Distal femur, proximal tibia and fibula, knee joint and patella.
Rt Knee Anatomy
Meschan, I. 1955 An Atlas of Normal Radiographic Anatomy
Saunders, London
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Basic Patient Position
The patient lies supine on the table legs extended and the
affected limb aligned to the long axis of the table. The leg is
rotated inwards until the femoral condyles are equidistant from
the film or the patella is midway between the femoral condyles.
The tibia should be parallel to the film.
Lt Knee Patient position
Meschan, I. 1955 An Atlas of Normal Radiographic Anatomy
Saunders, London
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Radiation protection
Direct lead rubber gonad protection using a "half
apron".
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Central Ray
The vertical central ray should be at 90 degrees to the tibia
and is centered to the joint space which is palpable laterally,
this point is generally about 2cm below the apex of the patella
and in line with the crease of the knee.
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Exposure Factors
| Kv |
mAS |
FFD (cm) |
Grid |
Focus |
AEC |
Cassette |
| 65 |
5 |
100 |
No |
Fine |
No |
18 x 24 cm |
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Evaluation of the Image
ID and markers must be present and correct in the appropriate
area of the film
Evidence of collimation on four sides equally around the
centering point.
Limits of the examination, superiorly the distal femur,
inferiorly the proximal tibia and fibula laterally and medially
the skin surfaces.
The joint space should be visualised with the proximal articular
surface of the tibia at 90 degrees to the film, the apex of the
patella should be in line with the tibial spines.
Optimal exposure should penetrate all the bone structures and
contrast should be low enough to visualise fully the bone and
soft tissue structures.
Lt Knee Radiograph
http://www.vh.org
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Related Projections
Knee Lateral
Femur Lateral and AP
Tibia and fibula AP & Lat.
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Additional modalities
CT
MRI
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