Knee Flashcards
routine views
AP view
Lateral view
PA “Tunnel” view
tangential “Sunrise” view of the patella
what to notice in an AP view
- patellar apex at level of joint line
- joint space heights (should be equal)
- tibiofemoral alignment
- view parallel to tibial plateau
AP view outline
Femur:
- epicondyles
- condyles
Proximal tibia
- condyles
- intercondylar tubercles
Proximal fibula
-head, neck, shaft
Patella:
- base
- apex
what to notice in a lateral view
- medial femoral condyle magnified (further from the plate)
- patellar tendon length=patellar length +/- 20%
- patellar alta (superiorly shifted)
- patellar baja (shifted inferiorly)
lateral view outline
Femur:
-condyles
Proximal tibia
- intercondylar eminence
- tibial tuberosity
Proximal fibula
-head, neck, shaft
Patella
Fabella (sesamoid bone in the gastroc)
PA tunnel view is best for:
- intracondylar notch should be U shape
- loose bodies in the joint
- joint space narrowing
- tibial plateau
*pt prone with knee flexed ~45 deg
PA tunnel view outline
Femur:
- epicondyles
- condyles
- intercondylar fossa
Tibia
- condyles
- intercondylar eminences
Fibula
- head
- neck
Tangential “sunrise” view of the patella is best for showing:
patellofemoral joint space (cartilage thickness)
patellar alignment
- sulcus angle
- congruence angle
- patellar tilt
*pt supine w/ knee flexed 45 deg
sulcus angle
(apex at point A)
-lines between the deepest point of the groove and the highest points of each femoral condyle
Normal= 138 deg (+/- 6 deg)
congruence angle
(angle cab)
- bisect sulcus angle (line ab)
- line between apex of sulcus angle and most posterior point on patella (line ac)
negative= medial
normal= -6 deg
lateral sublux= +16 deg
patellar tilt
(angle T)
angle between a line connecting medial and lateral edges of the patella, and the horizontal
normal= <5 deg
patellar malalignment
- spec=92%, sens=85%
- accuracy=89%
tangential “sunrise patella view outline
Femur:
- lateral condyle (lat. trochlear ridge)
- trochlear groove
- medial condyle (med. trochlear ridge)
Patella:
- lateral facets
- medial facets
Measure:
- sulcus angle
- congruence angle
- patellar tilt
distal femur fractures
supracondylar
- nondisplaced
- impacted
- displaced
- comminuted
condylar
intercondylar
fracture of the tibial plateau
often hard to see actual fracture, but can see the abnormal fat and blood within the capsule (MRI is better)
meniscal tears
common sports-related injuries. isolated tears present with intermittent clicking, locking, effusion and pain.
occur during shear, rotary, and compression forces.
medial meniscus is more frequently injured bc of its greater peripheral attachment and decreased mobility, impairing its ability to withstand imposed forces.
kinds of meniscal tears
vertical bucket handle peripheral horizontal discoid meniscus
normal ACL- MRI
- normal lat –> med course makes visualization of entire length difficult
- should be “ruler straight” possibly very slightly convex inferiorly
- segond fracture??
some reference measurements:
- Blumensaat line angle
- anterior tibial line
segond fracture
=fracture of the lateral tibial plateau
-often associated with internal derangements of the knee (mostly ACL)
blumensaat line angle
The ACL Blumensaat line angle is the angle between a line drawn parallel to the posterior surface of the femur a line along the margin of the ACL
this angle has a negative value when its apex is pointed superiorly and a positive value when its apex is pointed inferiorly
normal= -13 deg
*if 0: probability or normal=91%, probability of torn=9%
anterior tibial line
sagittal view half way through the lateral femoral condyle
- vertical line from posterior margin of tibia
- should not cut through
acute torn ACL- MRI
note the hemorrhage in intracondylar notch area
-bone bruises can often be seen in T2 weighted images
partial ACL tears
chronic partial ACL tears are difficult to see in absence of:
- segond fracture
- bone bruises
- hemorrhage
Blumensaat line angles can be normal
adjacent images can look OK
results in false negative reports
torn MCL
more commonly injured
by a valgus force
if deep and superficial layers are torn should be able to note the edema and joint effusion
lateral collateral ligament complex
LCL arcuate ligament fabellofibular ligament popliteus tendon biceps femoris tendon
patella alta
patella is too high
expect to see decreased strength bc patella isn’t acting as a good spacer to increase moment arm- quad may be too short
pittsburgh knee rules for conventional radiographs
History of blunt trauma/fall
AND EITHER OR BOTH OF:
- age 50
- inability to walk 4 WBing steps
sensitivity=99% (if you have it the test will be positive)
specificity= 60% (if you don’t have it the test will be negative)
Ottawa knee rules for conventional radiographs
(not to be applied if age 50
- tenderness at the fibular head
- isolated tenderness of the patella
- inability to flex knee to 90 deg
- inability to walk 4 WBing steps immediately (from hx) AND in clinic
sensitivity=97%
specificity= 27%
