w11 knee, patella, notch

plate size and orientation for knee

P 24x30

grid or non grid for knee

depends on thickness

pt positioning for AP knee

supine, legs extended, epicondyles equidistant, knee/ankle/hip aligned

how to find correct CR angle for AP/oblique knee

measure from ASIS to table

knee CR if ASIS to table is less than 18cm

5 degrees caudad

knee CR if ASIS to table is 19-24cm

perp

knee CR if ASIS to table is more than 25cm

5 degrees cephalad

goal of applying the angle for the AP knee

tibial plateau margins SI = open joint space

CP for AP knee

1cm inferior to patellar apex

if you can’t feel the patellar apex when finding the CP for the AP knee, what else can you use

1 inch distal to medial epicondyle

structures included for AP knee

1/4 femur, 1/4 tib/fib, ST

proper AP knee alignment

LA of knee to LA of IR

main goal for assessing good BTP for AP knee

anterior and posterior tibial margins SI prox/dist (aka open femorotibial joint)

for assessing good BTP for the AP knee, we want an open femorotibial joint. what else can we look at

top of the fibula should be midway between tibial plateau and point where metaphysis arises

when applying a beam angle to the AP knee, which structure will be projected (ie which one is hit first)

anterior tibial margin

what does too much cephalic angle look like on the AP knee

anterior margin is proximal to the posterior margin

what does insufficient cephalic angle look like on an AP knee

anterior margin is distal to the posterior margin

too much cephalic angle of AP knee is which type of E/D

ankle elevated to knee

insufficient cephalic angle of AP knee is which type of E/D

ankle depressed to knee

what is the main goal for assessing no rotation of the AP knee

femoral condyles are symmetrical

the main goal for assessing no rotation of the AP knee is symmetrical femoral condyles. what else do we look at (2)

tibia SI 1/2 of fibular head, intercondylar eminences are centered within the fossa

what does internal rotation of the AP knee look like (2)

lateral femoral condyle magnified, less SI of fibular head on tibia

what does external rotation of the AP knee look like (2)

medial condyle magnified, more SI of tibia and fibula

what does excessive cephalic angle of an AP knee do to the fibular head (2)

foreshortens it, places it lower on the tibia

what does insufficient cephalic angle of an AP knee do to the fibular head

distorts it, fibula too high on the tibia

why does an excessive cephalic angle of the AP knee make the fibular head lower on the tibia and not higher

beam angle hits the tibia first, projecting the tibia more proximal = fibula looks lower

pt positioning for medial oblique knee

from AP, medially rotate 45 degrees. elevate/support affected side hip if needed

CR for AP oblique knee

same as AP

CP for AP medial oblique

1cm inferior to patella apex + midway between lateral and medial borders of the knee

structures included for medial oblique knee

1/4 femur, 1/4 tib/fib, ST

main goal for good BTP for medial oblique knee

anterior and posterior tibial margins SI (aka open joint)

the main goal for good BTP for medial oblique knee is that the joint is open. what else do we look for

top of the fibula is midway between the tibial plateau and the point where the metaphysis arises

main goal for good medial obliquity of the knee

fibular head free of SI on the tibia (ie proximal tibiofibular joint is open)

the main goal for proper obliquity of the medial oblique knee = fibular head is free from tibia. what else do we look at (2)

1/2 patella free from the medial condyle, lateral condyle is in profile with no SI over the medial

what does excessive rotation look like on a medial oblique knee (4)

closer to lateral, femoral condyles more SI ant/post, can’t see fossa, more than ½ of the patella is free from the femur

what does insufficient rotation look like on the medial oblique knee (4)

closer to AP, condyles almost equal in symmetry, less than 1/2 of the patella is free of SI, fibular head slightly SI on tibia

pt positioning for the lateral oblique knee

from AP, rotate 45 degrees laterally. elevate/support the unaffected hip

CR for lateral oblique knee

same as AP

CP for lateral oblique knee

1cm inferior to patellar apex + midway between medial and lateral borders of the knee

structures included for lateral oblique knee

1/4 femur, 1/4 tib/fib, ST

main goal for good BTP for lateral oblique knee

anterior and posterior tibial margins SI (aka open joint)

the main goal for the lateral oblique knee having good BTP is an open joint space. what else do we look at

the top of the fibula is midway between the tibial plateau and the point where the metaphysis arises

what does good external obliquity look like for the lateral oblique knee (main goal)

fibula aligned with the anterior edge of the tibia

the main goal for assessing proper rotation for the lateral oblique knee is the fibula being aligned with the anterior edge of the tibia. what else do we look at (2)

1/2 of the patella is free from the lateral condyle, the medial condyle is in profile with no SI of the lateral

what does excess rotation look like on the lateral oblique knee

fibula in the posterior of the tibia, more than 1/2 of the patella is free

what does insufficient rotation look like for the lateral oblique knee

fibula not quite SI the tibia, more of the patella is SI

pt positioning for the lateral knee

pt lies on affected side, flex affected knee 20-30 degrees, patella perp to IR, femoral condyles SI

when standing, which femoral condyle projects more distally

none; they’re in the same transverse plane

when imaging in a supine position, which femoral condyle projects more distally

medial

what is the CR for a lat knee

5-7 degrees cephalad

why is the CR for the lat knee a cephalad angle

beam hits the medial condyle first and projects it upwards towards the lateral so the joint space appears open

CP for lat knee

knee joint (crease), midway between ant/post surface

structures included for lat knee

1/4 femur, 1/4 tib/fib, patella, tibial tuberosity, ST

when positioning the pt for a lat knee, why is a 20-30 degree flexion needed (ie what happens if there is less/more than this)

patellofemoral joint will close, distortion of bursa and fat pads occurs

what is the proper alignment for lat knee

site dependent; either femur, patella, or tib/fib will be aligned to the LA of the IR

good BTP for lat knee

femoral condyles SI prox/dist (open knee joint)

main goal for adequate rotation for lat knee

anterior aspects of femoral condyles SI ant/post (open patellofemoral joint)

main goal for good rotation for the lat knee is anterior aspects of femoral condyles SI ant/post. what else do we look for

1/2 fibular head SI over tibia

main goal for knee F/E for the lat knee

open patellofemoral joint

main goal for F/E of lat knee is open patellofemoral joint. what else do we look for

patella is proximal to the patellar surface of the femur

on the lat knee projection, how are we able to tell the medial condyle from lateral condyle

medial condyle has the adductor tubercle on the posterior/superior edge. it is also rounded and larger

what important structure must we see on the lat knee

suprapatellar fat pads

for the HB lat knee, which direction is the beam going

lateromedial

CR for HB lat knee

5-7 degrees caudad

why is the CR for the HB lat knee caudad, whereas the CR for the mediolateral knee cephalad

when we go lateromedial (in the HB one), the beam hits the lateral condyle first, so we need to project it downwards towards the distal medial condyle

PA knee pt position

pt prone, either feet off the table or feet on and dorsiflexed

pt position for AP WB knee

standing, back of knees to bucky, toes forward, condyles equidistant

CR for WB AP knee

perp

why is the CR perp for the AP WB knees

tibial plateau is flat when we stand, so we don’t need an angle

plate size and orientation for patella

P 18x24

what are the alternate names for the tangential patella (3)

skyline, sunrise, axial

pt positioning for tangential patella

sitting with sponge behind their back, knee flexed 40-60 degrees, femur/tibfib in straight line, IP has lead behind it

CR for tangential patella

parallel to the anterior patella surface (apex and base SI)

CP for tangential patella

mid patella at the level of the patellofemoral joint

good BTP for tangential patella

apex and base of patella SI (joint open)

what does too much cephalad angle do to the tangential patella

apex is anterior to base

what does insufficient cephalad angle do to the tangential patella

apex is posterior to base

good rotation for tangential patella

lateral femoral condyle is slightly anterior to the medial one

what does external rotation look like on the tangential patella

lateral condyle in the same horizontal plane as the medial one

what does internal rotation look like for the tangential patella

lateral condyle is much more anterior than the medial one

what does good knee flexion look like for the tangential patella

tibial tuberosity is posterior to the intercondylar surface

what does under flexion look like on the tangential patella

tibial tuberosity starts to appear in the joint space, patellofemoral joint will narrow

plate size and orientation for intercondylar fossa/notch

P 24x30

positioning for the AP notch

from AP flex pt leg by 60 degrees, put IP on a sponge under the leg, align hip to ankle

CR for AP notch

perp to the tib/fib

CP for the AP notch

knee joint

structures included for the AP notch

fossa, femoral condyles, proximal tib/fib, ST

goof BTP for the AP notch view (2)

fossa is open (no patella SI), tibial plateau is SI prox/dist

what does too much of a cephalad angle look like on the AP notch (2)

narrowed joint space, fibular head is too distal to the plateau

what does insufficient cephalad angle look like on the AP notch

narrowed joint space, fibular head too proximal to the plateau

what does good rotation look like for the AP notch (2)

medial and lateral surfaces of the fossa are in profile, 1/2 of fibular head SI by tibia

what does internal rotation look like for the AP notch

lateral condyle is wider, less SI of fibula on tibia

what does external rotation look like for the AP notch

medial condyle is wider, more SI of fibular head on tibia

what does good knee flexion look like for the AP notch

patellar apex is just proximal to the fossa

what does excess knee flexion look like for the AP notch

patellar apex moves into the fossa