X-ray Projections Of The Knee Flashcards
What does the knee include?
(4)
Femoral condyles
Tibial plateau (the flat bit at the top of the tibia)
Fibula head
Apex of the patella
What are the projections of the knee?
(3)
AP
Lateral
Skyline patella
How can we do an AP projection of the knee?
(2)
Seated/supine
Weight bearing
Why is the patella important?
It protects the knee from friction when doing flexion and extension
How can we do a lateral knee projection?
(2)
Turned
HBL
How do we position a patient for an AP knee?
(5)
Patient seated with knees extended
Patient stood for weight bearing views
Affected knee’s patella is rotated to be midway between the condyles
The detector is as close to the back of the knee as possible
Centre the beam 2.5am below the apex of the patella
Label the information for an AP knee:
What do we do if the patient if they can’t extend their knee?
Raise the detector then angle the tube so it stays perpendicular to the tibial plateau
How do we position for a lateral knee projection?
(5)
From the AP position, turn the patient 90 degrees towards the affected side
Flex the knee to 90 degrees
Raise the foot with a small pad to ensure that the tibia is parallel to the detector if needed
Adjust the femoral condyles so they’re superimposed
Central beam 2.5cm below and behind the apex of the patella
Answer the information on doing a lateral knee x-ray:
How should an AP knee x-ray look like?
How should a lateral knee x-ray look like?
How do we know that the condyles aren’t superimposed meaning we need to redo the x-ray?
(3)
Too much of the fibula is visible, so the patient is externally rotated too much
Not enough of the fibula is visible, so the patient is internally rotated too much
Check that the tibia is parallel to the detector
How can we adapt technique for a trauma patient’s knee x-ray?
Horizontal beam lateral (HBL)
How do we do a HBL knee x-ray?
Place the detector between the patient’s legs and direct the beam medially
Why would a HBL projection be used?
(2)
Trauma patient
Lipohaemathrosis (there’s fractures within the joint capsule that release blood and fat from the bone marrow, causing the blood to sink and fat to float)
How do we position for a skyline patella?
(4)
Assess the retro-patella joint space
Flex the knee 30-45 degrees
Ask the patient to hold the detector
The central ray is slightly cranially (bent upwards)
What are orthopaedic special requests for a knee x-ray?
(2)
Intrcondylar notch (tunnel) view
Rosenberg knee view
How do we position for an intercondylar notch (tunnel) view?
(3)
The patient is supine with knees flexed to 40 degrees
The detector is under the knee (like in AP)
The central beam is perpendicular to the tibial plateau
Why is an intercondylar notch (tunnel) view done?
To visualise the tibial plateau and femoral intercondylar spaces
How do we position for a Rosenberg knee view?
(4)
PA weight bearing (use PA marker)
Knee at 45 degree flexion
The centre beam is 15 degrees caudad
Centre 1.5cm below the apex of the patella
Why is a Rosenberg view done?
Because the joint space is narrowing
What type of bone is the patella?
A sesamoid bone
What does a loss of joint space/osteoarthritis look like?
