MRI of Knee Flashcards
essential MRI sequence for examining the menisci
sag T1 or PD
knee should be in what position during MRI
externally rotated about 5 to 10 degrees
3 MRI sequences to examine cruciate ligaments and cartilage
FSE, T2 or T2* GRASS
used to examine the collateral ligaments and cartilage and look for meniscocapsular separations
coronal images
used for viewing the patellofemoral cartilage, identifuing bursal fluid collections and for a second look at the cruciate and collateral ligaments
axial images
a fibrocartilaginous, C-shaped structure that is uniformly low in signal on both T1 and T2 weighted images
menisci
meniscal signal that does not disrupt an articular surface is representative of
instrasubstance degeneration
high signal in meniscus disrupts the superior or inferior articular surface
meniscal tear
most common type of meniscal tear
oblique horizontal tear extending to the inferior surface of the posterior horn of the medial meniscus
type of meniscal tear that occurs along a plane perpendicular to the long axis of the meniscus and involves at least tje inner free edge portion of the meniscus; if large, a radial tear may extend across the full width of the meniscus
parrot beak or radial tear
ACL tears usually happens at the
periphery of the menisci
lateral meniscus tears happen at what portion of the menisci
posterior horn
longitudinally-oriented tear of the mensicus resulting in inner free edge of the meniscus becoming displaced towards the intercondylar notch
Bucket-handle tear
only one image is present that has the bow-tie appearance of the body segment of the meniscus
Bucket-handle tear
normal size of meniscus
9 to 12 mm wide and 4- 5 mm thickness
large meniscus that can have many different shapes; lens-shaped, wedged, flat
discoid meniscus
discoid meniscus is commonly seen in what meniscus
lateral meniscus
lateral meniscus often has what appears to be a tear on the anterior horn near its upper margin, which is a ______ from the insertion of the transverse ligament
pseudotear
seen in the intercondylar notch as a linear, predominantlly low signal structure on T1. often shows some linear striations onto the medial tibial spine when viewed on sagittal images
ACL
when ACL is torn, it appears
it is not visualized
partial tears or sprains of the ACL are manifested by
high signal and/or laxity within an otherwise intact ligament
gently curved, homogeneously low-signal structure that is infrequently torn or even less frequently repaired by surgeons. when torn, it appears thickened and it has diffuse intermediate signal throughout
posterior cruciate ligament
normal size of PCL
6 mm or less in diameter
when PCL is torn, it has a thickness of
7mm or thicker
low-signal, round structure often seen just anterior or poterior to the PCL, as seen in sagittal views. a loose body or displaced fragment of a piece of torn meniscus can have this appearance
meniscofemoral ligament
a meniscofemoral ligament passes infront of PCL, it is called _____; if it passes behind the PCL, it is called _____
ligament of Humphrey (anterior), ligament of Wrisberg (posterior)
originates in the medial femoral condyle and inserts on the tibia. it is closely applied to the joint and is intimately associated with the medial joint capsule and medial meniscus
MCL
injuries to MCL usually occur from
valgus stress to the lateral part of the knee (such as clipping injury in football)
grade of MCL injury: mild sprain and is diagnosed on MR by the presence of fluid or hemorrhage in the soft tisue medial to the MCL. ligament is otherwise normal
grade 1
grade of MCL injury: partial tear and is seen as high signal in and around the MCL on T2 and T2* coronal sequences. ligament is intact, altho the deep or superficial fibers may show minimal disruption
grade 2
grade of MCL injury: complete disruption of MCL
grade 3
speckled appearance of anterior horn of lateral menscus, normal or abnormal
normal variant
occurs when the medial meniscus is torn from its attachment to the joint capsule. this occurs most commonly at the site of MCL and often occurs concomitantly with an MCL injury
meniscocapsular separation
this ligament consist of 3 parts; most posterior is the tendon of biceps femoris, which inserts onto the head of fibula. next, anterior to the biceps, which extends from the lateral femoral condyle to the head of fibula
LCL
anterior to the fibullar collateral ligament is the _____, which extends into the fascia more anteriorly and inserts onto Gerdy tubercle on the tibia
iliotibial band
patellar cartilage commonly undergoes degeneration, cuasing exquisite pain and tenderness. this is called
chondromalacia patella
a frequent cause of a patellar cartilage defect is
dislocation of patella
normal structure seen in over half of the population, which is an embryologic remnant from when the knee was divided into three compartments. it is a thin fibrous band that extends from the medial capsule towards the medial facet of the patella
patellar plica
when a patellar plica cause clinical symptoms that are indistinguishable from those of a torn meniscus, it is termed
plica syndrome
represents microfractures from trauma. they are easily identified on T1W images as subarticular areas of inhomogeneous low signal. in T2, it demonstraes increased signal for several weeks depending on its severity
bone contusions
bone contusions can progress to _____ if they are not treated with decreased weight bearing
osteochondritis dissecans
a commonly seen bone contusion is one that occurs on the posterior part of the lateral tibial plateau with an associated “kissing” contusion in the central to anterior lateral femoral condyle. this has been called
“pivot-shift” contusion pattern
a fracture that is almost always associated with an internal derangement is the _____. A small, bony fragment pulled off the lateral tibial joint line by an avulsion of the lateral joint capsule, it is almost always associated with an ACL tear
Segond fracture
an abnormality that can cause joint pain and clinically mimic plica syndrome or a torn meniscus is
bursitis
an uncommon medial bursa; three tendons– the sartorius, gracilis and semitendinosus—insert onto the anterior medial aspect of the tibia in a fan-shaped manner that has been likened to a Goose’s foot. the bursa lies beneath the insertion site, which can be inflamed and cause medial joint line or patellar pain and can be confused clinically with a torn medial meniscus
pes anserine bursa
much more common medial bursa that occurs at the medial joint line and often mimics a meniscal cyst. it has a characteristic comma shape as it drapes over the semimembranosus tendon
semimembranosus tibial collateral ligament bursa
