2. Important Information
Number of projections:
Trauma series knee: 4 projections
Nontrauma series knee: 4 projections
The projections include: AP, AP Erect, Lateral Knee, Medial
Oblique, Lateral Oblique, AP Axial (also known as Be’clere)
Prep:
No internal or external preparations are necessary for this exam.
Clothing (specifically pants) need to be removed if the patient
is unable to pull their pants above their knee for the x-rays.
Reasons for study:
Helps to determine reasons for pain, swelling, or discomfort. Also
to look for broken bones or dislocated joints. May either be
required before knee surgery or after to assess the results of the
operation. Also, a knee X-ray can help to diagnose later stages
of infection, as well as cysts, tumors, or other diseases in the
bone.
Length of study: Should be a fairly quick procedure
3. Patella
The patella is a
very important part
of the knee
because a lot of
the projections that
are being
reviewed are
centered near the
patella.
The base is superior
to the apex.
4. AP Image
Used for both trauma and nontrauma related
Image receptor: 10 x 12
SID: 40 inches
Patient will be lying supine, pelvis not rotated
Central Ray: ½ inch inferior to the patellar
apex (which will center the IR to the joint
space), also at a variable angle because you
will measure between the anterior superior
iliac spine (ASIS) and the table top to find
degree of the angle of the central ray.
Shield gonads
18 cm and below: 5 degrees caudad
19-24 cm: perpendicular
25 cm and above: 5 degrees cephalad
6. Lateral Image
Used for both trauma and nontrauma projections
Image receptor: 10 x 12
SID: 40 inches
Patient will be lying on affected side, bring knee
forward and extend the other limb. Flex affected
knee between 20 and 30 degrees to show
maximun volume of joint cavity. Only flex it 10
degrees if the knee is newly injured or unhealed
Central ray: directed to
knee joint 1 inch distal to
the medial epicondyle at
an angle of 5-7 degrees
cephalad.
Shield gonads
9. AP Erect
Used for nontrauma
pictures
Image receptor: 14 x17
(book shows bilateral
positioning)
SID: 40 inches
Patient stands straight up,
feet at a good distance
apart, knees fully
extended.
Central ray: will be placed
horizontally and
perpendicular to the
center of the IR, entering
at a point ½ inch below
the apices of the patella
10. AP Axial or Be’Clere
Used for nontrauma
knees
Image receptor: 8 x 10
crosswise
SID: 40 inches
Patient is supine, flex
affected knee enough
to place the long axis of
the femur at an angle
of 60 degrees
Central ray:
Perpendicular to the
long axis of the lower
leg, entering the knee
joint ½ inch below the
patellar apices.
Shield gonads
12. Lateral (External) Oblique
Used for trauma views
Image receptor: 10 x 12
SID: 40 inches
Patient is in a supine
position, externally rotate
the leg 45 degrees
Central ray: will enter ½
inch inferior to the
patellar apex, and again
the angle is based on the
measurement between
the ASIS and the table
top.
Shield gonads
13. Medial (Internal) Oblique
Used for trauma views
Image receptor: 10 x
12
SID: 40 inches
Patient is lying supine,
medially rotate the
affected side to a 45
degree angle
Central ray: will enter
½ inch inferior to the
patellar apex, angle is
variable and based on
the measurement
between the ASIS and
the table top
Shield gonads
