Indications for imaging
Trauma, bone pain, arthritis, joint replacements, soft tissue
calcifications loose bodies, osteosarcoma, Bakers cyst (a collection of
sensorial fluid which has escaped from the knee joint or a bursa and formed a new
sensorial-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.
Lt Knee anatomy
Meschan, I. 1955 An Atlas of Normal Radiographic Anatomy
Saunders, London
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Basic Patient Position
(Non Trauma)
The patient lies on the affected side and the upper limb is
flexed maximally and drawn up over and in front of the affected
limb and supported suitably. The knee of the affected side is
flexed 45 degrees. The femoral condyles should be in
vertical alignment and the tibia parallel to the table.
(Trauma cases require a horizontal ray lateral)
With the patient supine on the table and the affected limb
aligned to the long axis of the table. A small support is placed
under the knee to raise the knee and support it in approximately
25 degrees of flexion.
Rt Knee Lateral Patient position (Non trauma)
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
(Non Trauma)
The vertical central ray is centered to the palpable joint space
immediately above the palpable tibial expansion.
(Trauma cases require a horizontal ray lateral and usually a
latero medial central ray))
The horizontal central ray is centered to the joint space
approximately 2 cm below the femoral condyle, note this
projection may be medio lateral or latero medial.
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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 femoral condyles should be superimposed, the lower border
superimposition is affected by the angle between the femur and
the central ray whilst alignment of the posterior borders is
affected by the amount of rotation along the axis of the femur.
optimum positioning will superimpose the anterior half of the
fibula head on the tibia The tibia spines should be
superimposed and the tibia plateau should be seen end on. The
patella should be in profile and not superimposed on the femur.
Optimal exposure should penetrate all the bone structures and
contrast should be low enough to visualise fully the bone and
soft tissue structures.
Rt Knee Lateral Radiograph
http://www.vh.org
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Related Projections
Knee AP
Femur Lateral and AP
Tibia and fibula AP & Lat.
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Additional modalities
CT
MRI
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