Knee and Patella Flashcards
Knee - AP projection
supine with leg fully extended
- toes up
femoral condyles parallel to IR
- may require 5 internal rotation
CP: 1/2 inch below patellar apex
CR: Variable
AP Knee CR angles based on hip height measurments
18 cm and below - 5 caudad
19-24 cm - perpendicular
25 cm and above - 5 cephalad
what is the other way you can determine angle of the AP knee?
match tube angle to the tibia and reduce CR angle by 5 degrees
Knee - AP evaluation criteria
open femorotibial joint space
no rotation
- femoral condyles symmetrical
- slight superimposition of fibular with tibia
- petal superimposed on femur
Knee - PA projection
Patient is prone with top of toes on table
femoral condyles parallel to IR
CR: perpendicular
CP: Exit 1/2 inch below apex
Marker face down
Knee - PA evaluation criteria
open femorotibial joint space
no rotation
- femoral condyles symmetrical
- slight superimposition of fibular with tibia
- petal superimposed on femur
Knee - AP Medial Oblique projection
rotate entire leg 45
- elevate hip at affected side
- may need to use sponge
CR: Variable
CP: 1/2 inch below apex
Knee - AP Medial Oblique evaluation criteria
open proximal tib/fib joint
both tibial plateaus
lateral femoral/tibial condyles
medial border of patella
open knee
Knee - AP Lateral Oblique projection
rotate entire leg 45
- elevate unaffected hip
- may need sponge
CR: variable
CP: 1/2 inch below apex of patella
If doing a knee series of AP, AP medial oblique and AP lateral oblique, what order should you complete the images?
AP, AP lateral oblique then AP medial oblique, as the medial oblique will change the CR angle much more than the lateral (may not change at all)
Knee - AP lateral oblique evaluation criteria
medial femoral and tibial condyles
tibial plateaus
open knee joint
lateral border of patella
fibula superimposed with lateral half of tibia
Knee - PA internal and external oblique
patient prone, full leg rotated
CR: perpendicular
Marker: face down
Knee - Lateral projection
mediolateral
affected knee bent 20-30
- maximum of 10 if patellar injury
- pretend patellar injury is not a risk for practical exam
femoral condyles superimposed
CR: 5-7 cephalad
CP: 1 inch below medial condyle
Knee - lateral evaluation criteria
femoral condyles superimposed
open femerotibial joint space
open patellafemoral joint space
fibular head slightly superimposed with tibia
How to tell if a knee is under rotated?
locate adductor tubercle of medial condyle
more superimposition of tibia and fibula
how to tell if a knee is over rotated?
locate smooth posterior surface of lateral condyle
less superimposition of tibia and fibula
Knee - Trauma cross table lateral projection
lateromedial
demonstrates fat/fluid levels
- lipohemarthrosis
turn detector so grid lines are going vertical
marker - face down
bring the leg in 5-7 degrees
CR: horizontal
CP: 1 inch distal to lateral epicondyle
What does varus mean?
towards midline
What does valgus mean?
away from the midline
What does erect imaging of the knee demonstrate?
progression of arthritis
joint space narrowing
varus and valgus deformities
Knees - AP standing projection
Bilateral, weight bearing
- no shoes
True AP - condyle parallel to the IR
CP: 1/2 an inch below the apex of the patella
CR: 5 caudad for average patient - perpendicular for larger patients
Marker: L and R and up arrow
Knee - PA standing projection
weight bearing
Legs flexed 45
- toes level to the IR
- knees against the Bucky
be careful shielding is not blocking your image
CP: Exit 1/2 inch below apex
CR: 10 caudad
Marker: facedown with arrow up
Knee - PA standing evaluation criteria
both knees without rotation
tibial plateaus in profile
intercondylar fossae visible
What is joint mince?
loose bodies in the intercondylar joint space
Knee - PA Axial Tunnel - Holmblad Method - projection
Patient kneeling on table
- unaffected knee on sponge
- affected femur bent 20 to CR, or 70 to table
CR: perpendicular
CP: crease of knee
Marker or Shielding
Knee - PA Axial Tunnel - Holmblad Method - evaluation criteria
open intercondylar fossa
posterioinferior surface of condyles
plateaus should be in profile
visible intercondylar eminence
no rotation
Knee - AP Axial Tunnel - Béclère method - projection
patient supine
- knee flexed 60 to long axis of tibia
IR non grid under knee on sponges
CR: align with tibia and reduce by 5 degrees
SID: 102 cm
CP: Knee joint
Knee - AP Axial Tunnel - Béclère method - evaluation criteria
open intercondylar fossa
posterioinferior surface of condyles
plateaus should be in profile
visible intercondylar eminence
no rotation
Knee - PA Axial Tunnel - Camp-Coventry Method - projection
patient prone
- flex knee 40-50
use sponge
CR: 35-45 caudad (plateau)
CP: exit at the apex of the patella
Marker: face down
SID: 102 cm
Knee - PA Axial Tunnel - Camp-Coventry Method - evaluation criteria
open intercondylar fossa
posterioinferior surface of condyles
plateaus should be in profile
visible intercondylar eminence
no rotation
What is the patella?
it is a sesamoid bone
develops in the quadriceps femurs tendon
it is the largest sesamoid bone
What is the fabella?
develops in the tendon of the lateral head of the gastrocnemius
Patella - PA/AP projection
patient prone or supine
- PA provides improved spatial resolution because of the OID
patella must be parallel to the IR
- 5-10 internal rotation
CR: perpendicular
Collimate to just beyond patellar borders
Patella - AP/PA evaluation criteria
patella completely superimposed by femur
no rotation
marker in correct orientation
- face down for PA and face up for AP
Patella - lateral projection
lateral knee position
knee flexed 5-10
CR: perpendicular
CP: midpatellofemoral joint
Patella - lateral evaluation criteria
evidence of proper collimation and the presence of a side marker
knee flexed 5-10
patella in lateral profile
open patellofemoral joint space
Patella - tangential - inferosuperior projections
skyline/sunrise
Hughston
Settegast
Patella - Hughston Method projection
Prone
Knee flexed 30-45 from perpendicular
CR: 15-20 from long axis of lower leg
- tangential to patellofemoral joint space
SID: 102 cm
Patella - Skyline Supine - Projection
Patient supine near end of table
Flex knees 30-45
IR on mid thigh patella to tube head
CR: 15-20 from long axis of lower leg
Patella - Skyline Sitting - projection
similar to supine version
use thyroid, thorax and gonadal shielding
Patella - Settegast method - prone - projection
prone
knee flexed 90
CR: 15-20 from long axis of lower leg
do not attempt until a transverse fracture has been ruled out
Patella - Settegast method - sitting - projection
patient sitting near end of table
knee flexed 90
use thyroid, thorax and gonadal shielding
CR: 15-20 from long axis of lower leg
do not attempt until a transverse fracture has been ruled out
Patella - tangential projections - evaluation criteria
patella in profile
- inferior and superior borders superimposed
open patellofemoral joint
anterior surfaces of femoral condyles
very good for visualizing vertical fractures
