Knee Flashcards
most common direction of dislocation?
anteriorly
vascular injury with knee dislocation?
commonly popliteal injury
imaging recommendation for knee dislocation?
CT angiography
anatomic patellar variants
bipartite/multipartite patella and dorsal defect
patellar fracture mechanism?
direct blow; extreme sudden tension of the extensor mechanism
classification system for tibial plateau fractures
Schatzker classification
which fractures are more stable? lateral or medial tibial plateau?
lateral plateau fractures are more stable
which horn is bigger in the medial meniscus? which horn is bigger in lateral meniscus
medial meniscus: posterior
lateral meniscus: same size bilaterally
attachment of meniscus?
anterior/posterior meniscal root; injury causes extrusion
name the meniscofemoral ligaments and the landmark?
ligament of Humphry (anterior to PCL)
Ligament of Wrisberg (posterior to PCL)
what is the red zone of menisci?
outer zone; more likely to heal bc more vascular
how to differentiate between myxoid degeneration vs tear?
tear extends to articular surface ; myxoid degeneration doesn’t
most common type of meniscal tear? location? cause?
horizontal/oblique tear most commonly occurs in posterior horn of medial meniscus
most commonly due to degenerative changes
best view to see longitudinal/vertical tears?
sagittal views; fixed distance from edge of meniscus
cause of bucket handle tear?
extension of vertical tear with a free inner edge of meniscus
most common location for bucket handle tear? where does displaced fragment commonly go?
medial meniscus; displaced fragment ends up in intercondylar notch most commonly (but can also go anterior/posteriorly)
“absent bowtie” sign
“double delta” sign
“double PCL” sign
absent bowtie: fewer than 2 bowties on adjacent slices double delta sign: anterior displacement (sagittal) posterior displacement (sagittal; medial meniscus)
vertically oriented tear perpendicular to meniscus arc
radial or transverse tear
marching cleft sign
radial tear changes position relative to edge of meniscus
may look identical to a longitudinal tear/vertical tear on a single sagittal image.
ghost meniscus sign
no meniscal tissue seen when plane of imagine is directly through the radial tear
high rate of meniscal extrusion associated with what type of tear?
radial tear –> osteoarthritis
cause of meniscal cyst?
extension of joint fluid through meniscal tear
meniscal cyst associated with what type of tear?
horizontal cleavage
what is a discoid meniscus?
congenital malformation; increase thickness of meniscus, extends into central tibial plateau
problem with discoid meniscus?
increase risk of joint line pain, clicking, locking in kids/adolescents; prone to cystic degeneration/tear
most common location for discoid meniscus
lateral meniscus
MRI diagnosis of discoid meniscus
3 contiguous sagittal slices of oval/bow-tie shaped menisci (4 mm thick, so 12 mm) ; loss of central tapering/bowtie
attachments of ACL?
femoral intercondylar notch and attaches to the anterior tibial plateau, lateral to the spine
number of fiber bundles in ACL
anteromedial band and larger posterolateral band
MRI findings ACL tear
frank discontinuity of fibers or abnormal course/signal; may also see secondary buckling of PCL due to anterior displacement of tibia (positive drawer sign)
bone contusion in the lateral femoral condyle and the posterolateral tibial plateau
O Donoghue’s Triad
ACL, meniscal, MCL tear; posterolateral corner knee injury
XR findings ACL tear
Segond fracture; lateral tibial plateau (ACL and IT band injury) avulsion fracture
detachment of lateral capsular ligament
Where does IT band insert?
Gerdy’s tubercle of tibia
Blumensaat’s line?
drawn along intercondylar roof
ACL graft course?
behidn blumensaat’s line parallel to intercondylar notch
ACL graft too steep?
ACL graft too lax?
graft impinged with leg extension by femur
graft not enough stability
cyclops lesion? postop ACL?
nodular scarring of Hoffa’s fat pad; nodular soft tissue
which is thicker? ACL vs PCL?
PCL
insertion sites of PCL
femoral intercondylar notch more anteriorly than ACL and inserts on posterior tibial plateau
MR of PCL injury
laxity of PCL; ? abnormal high T2 signal
MCL ligament attachments
posterior aspect of medial femoral condyle; medial tibial metaphysis, deep to pes anserinus
MCL is extrasynovial (not seen on arthroscopy); intlaced with medial meniscus
MCL injury grading
Grade I: sprain
Grade 2: severe sprain/tear; Grade 3: complete tear
What is a pellegrini stieda lesion?
post traumatic calcification medial to medial femoral condyle
composition of LCL
biceps femoris, LCL, IT band
posterolateral corner components
LCL complex: BFT, LCL, IT band
Arcuate ligament (Y shaped), connecting fibula to lateral femur
Popliteofibular ligaments
Popliteus tendon (lateral femur insertion)
IT band syndrome
friction between anterolateral femur/tendon of IT band; anterolatearl knee pain common in runners
insall salvati ratio?
patellar tendon length to patelar length
patella alta ratio? baja?
alta >1.2, baja < 0.8
extensor mechanism of quadriceps?
quadriceps tendon, patella, patellar tendon
quad muscles: vastus intermedius, medialis, lateralis (from femur)
rectus femoris arises from AIIS
clinical presentation of quadriceps tendon tear?
loss of extension
common site of quadriceps tear?
within 2 cm of patella; results in patella baja
cause of patella alta?
tear of patellar tendon, superior displacement of atella
jumper’s knee?
patellar tendinosis; thickening of tendon
where are bone marrow contusions from patellar dislocation? what happens to medial retinaculum
lateral femoral condyle and medial patellar facet; tearing of medial retinaculum
osteochondrosis of tibial tuercle?
osgood schlatter disease; repetitive microtrauma?
Imaging findings of osgood sclatter XR, MR
XR: tibial tuberosity fragmentation/edema
MR: increased distal patellar tendon signal, bone marrow edema, edema within hoffa’s fat pad
divide compartments of knee
patellofemoral (medial, -median ridge -lateral, odd facets)
trochlear cartilage: medial, central, lateral
medial tibiofemoral
lateral tibiofemoral
types cartilage injuries to the knee
thinning
surface irregularity, fissuring, delamination (dissecting detachment)
etiology of osteochondrosis disseicans (OCD)
repetitive trauma in adolescents….cartilage dehydration and subsequent stiffening transmitting greater force to subchondral bone during loading
common locations for OCD
knee (lateral medial femoral condyle); ankle (posteromedial/anterolateral talar dome), elbow (gymnasts; anterolateral capitellum)
unstable OCD?
fragment unattached to bone –> secondary OA
PVNS? most common location?
benign; hyperplastic proliferation of synovium within the joint; outside joint –> giant cell tumor
knee
PVNs presentation
knee swelling, recurrent dark brown effusions from hemorrhage –> hemosiderin deposits and cause blooming artifact
lipoma arborescens?
overgrowth of intracapsular synovial fatty tissue –> fatt masses –> premature OA
treatment for lipoma arborescens
synovectomy
common location for baker’s cyst? ddx?
semimembranous tendon and medial head of gastrocnemius muscle
ddx: popliteal aneurysm
tennis leg?
tear of plantaris tendon or medial head of gastrocnemius
