Knee

Melissa Tobias

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

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.

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 caudad19-24 cm: perpendicular25 cm and above: 5 degrees cephalad

AP Images

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

Lateral Images

Nontrauma Images

AP Erect and AP Axial (Be’clere method)

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

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

Trauma Images

Lateral (External) Oblique Medial (Internal) Oblique

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

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

THE END