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BY: DR NIKHIL BANSALRESIDENT RADIO-DIAGNOSIS
UNDER GUIDANCE OF:
DR ANAND VERMA HOD (RADIO-DIAGNOSIS)
MGMC&H
RADIOLOGICAL ANATOMY OF KNEE
JOINT
INTRODUCTION The knee joint is one of the
important weight-bearing joints of the human body
Complex and extensive movements are performed , involving numerous active and passive mechanisms.
Knee is more l ikely to be damaged than most other joints because it is subject to tremendous forces during vigorous activity.
Therefore not surprising that the knee is frequently aff ected by traumatic and degenerative condit ions
PROTOCOL Field of view (FOV) --small 10
to 14 cm
A matrix of 256 x 256 is usually standard.
Dedicated knee coil is mandatory as it improves the signal to noise ratio
Patient Positioning Supine, with the leg in full extension. The knee is placed in 10 to 15° of external
rotation(esp for sagittal image)
Slice Thickness 3-4 mm sections are used for axial, coronal
and sagittal images of the knee. Adults: 4mm Children's: 3mm 3DFT(Fourier Transformation) Sub
centimeter
Imaging Planes and Pulse Sequences
Short echo time (TE) conventional spin echo (CSE) images generally provide the best contrast for anatomical evaluation
Proton-density images are probably the most sensitive for detection of meniscal tears.
FSE T2-weighted images have demonstrated high accuracy for detection of cartilage lesions.
3D Fourier transformation (3DFT) Imaging is becoming popular
-provides the highest resolution -with an acceptable S/N ratio -allowing image reconstruction in any
plane.
Knee protocol
Fast spin echo PD and T2w in the sagittal plane (meniscal, cartilage)
STIR sequence in the coronal plane(marrow)
T1W coronal images
T2W axial images
General anatomy Knee is the largest and more complex joint of the
body Complexity is the result of fusion of three joint - lateral t ib iofemoral jo int - medial t ib iofemoral jo int
- femoropatel lar jo int It is a compound synovial joint ,incorporating two
condylar joints between condyles of femur and tibia and one saddle joint between femur and patella.
ARTICULAR SURFACEFormed by – condyles of femur , patella and
condyles of tibia
X-Ray
Sartorius
INRACAPSULAR LIGAMENTS1. Anterior cruciate ligament2. Posterior cruciate ligament3. Medial meniscus4. Lateral meniscus5. Transverse ligament
Menisci: The menisci of the knee are two
semilunar, C-shaped fi brocart i laginous disks that s i t on the per ipheral margins of t ib ia l p lateau
Upper surfaces of both menisci are concave, and they art iculate with the convex femoral condyles.
Each meniscus has two ends which are attached to t ib ia, and two borders
(a)The outer border is thick , convex and fi xed to the fi brous capsule
(b) Inner border is thin concave and free.
Micro-anatomy: Type 1 Collagen
Red Zone: 1/3White Zone: 2/3
They measure ~3 to 5 mm in height at the periphery ~1 mm or less at the free edge.
MEDIAL MENISCUS
Medial meniscus is shaped more l ike a half-c irc le.(open “C”)
The width of the medial meniscus, in contrast to the lateral meniscus, gradual ly tapers from posterior(12mm) to anterior(6mm)
Peripheral margin of the medial meniscus is more fi rmly attached to the t ibial col lateral l igament.
MRI APPEARANCEANTERIOR & POSTERIOR HORNS- Best demonstrated on sagittal viewBODY of meniscus- Best seen on coronal images
Lateral meniscus
The lateral meniscus has the same width throughout, approximately 10 mm
Peripheral margin of the lateral meniscus is attached to the capsule except poster lateral , where the popl iteal tendon crosses it , and more posteriorly and central ly near the central attachment site, where the capsule does not extend anteriorly into the joint.
Anterior horn of lateral meniscus
The anterior and posterior horns of the lateral meniscus are about equal in size
Anterosuperiorly transverse l igament is attached to it .
Posterior horn of lateral meniscus
It differs from medial meniscus
its attachment to the capsule is interrupted by the popliteal tendon,
Superiorly it gives origin to ligament of wrisberg ( meniscofemoral ligament) which appear as round dot adjacent to superior aspect of the posterior horn
Discoid Meniscus
A discoid meniscus refers to a meniscus, almost always the lateral one, that is not C-shaped but disklike.
it covers most of the tibial plateau to varying degrees rather than just its periphery.
is usually seen in children and adolescents, in whom it may be asymptomatic and noted incidentally.
It is prone to tearing The prevalence of discoid lateral
meniscus (1.5%-15.5%) is greater than that of discoid medial meniscus
High-resolution coronal images allow better depiction of this enlarged meniscus.
A discoid meniscus is said to be present if three or more 5mm-thick contiguous sagittal images demonstrated continuity of the meniscus between the anterior and posterior horns.
Another criteria was height difference of 2mm on coronal image.
Lateral meniscus from the periphery to the notch
Normal lateral meniscus.
Discoid lateral meniscus
Pitfalls…
The posterior horns are seen on coronal views as flat bands that should not be confused with discoid menisci
NORMAL VARIATIONS AND PITFALLS 1. Wrisberg and Humphry Ligaments: The meniscofemoral ligaments of Wrisberg and Humphry originate from the superior aspect of the posterior horn of the lateral meniscus.
The Wrisberg ligament is located posterior to the posterior cruciate ligament and seen in 33% sagittal image.
The Humphry ligament is anterior to the posterior cruciate ligament
1 of these 2------ 70 % Both---------------6%
Ligament of Wrisberg
Ligament of Humphry
Popliteus Tendon
Popliteus tendon and its hiatus separate the lateral meniscus from the joint capsule.
Signal intensity from the popl iteus tendon sheath or fl uid within its hiatus could be mistaken for a meniscal tear on both sagittal and coronal images
T 1w show the popliteus tendon. as it courses medially and inferiorly in the more medial section.
(a) Image shows the tendon above the lateral meniscus.
(b) Image shows the tendon (arrow) has moved behind the meniscus.
(c) Image shows the tendon (arrow) is inferior to the meniscus.
Transverse Ligament
Connects the anterior horns of both menisci
The signal intensity produced from the loose connective t issue between the transverse l igament and the most medial part of the anterior horn of the lateral meniscus can be mistaken for a meniscal tear.
This error can be avoided by tracing the cross-section of the l igament through the infrapatel lar fat pad on more central MR imaging sections
Sagittal fat suppressed
Medial--lateral
CENTRAL STRUCTURES OF KNEE
Anterior Cruciate Ligament
Anatomy extends from its semicircular attachment at the lateral femoral condyle to the
anterior intercondylar region of the tibia. It is just posterior to the transverse
ligament and just anterior to the central attachment of the anterior horn of the lateral meniscus where some fibers mix.
The tibial attachment is larger than the femoral and fanlike in shape.
ligament measures approximately 4 X 1 cm
may consist of two or more distinct bundles separated by loose connective tissue and fat, more prominent at the mid- and distal portions.
MRI Appearance
ACL is best seen on sagittal oblique images with slices parallel to the cortex of the lateral femoral condyle.
ACL may appear as a solid low-signal-intensity band
Coronal image
ACL as a c fanlike structure adjacent to the horizontal segment of the PCL near the medial surface of the lateral femoral condyle
Proximally, the signal intensity is uniformly low, whereas distally it may be slightly increased.
ACL: Origin to insertion
Posterior Cruciate Ligament Anatomy The PCL arises at the lateral surface of the medial
femoral condyle and extends to the posterior surface of the intercondylar region below the level of articular surface of tibia.
It is wider and thicker than the ACL. Sagittal images best show the PCL; it appears as a
uniformly low-signal-intensity structure and arcuate in shape in routine MR imaging
It has a nearly horizontal takeoff at the femoral origin and then an abrupt descent at about 45 degrees to the tibia.
AXIAL SECTION SAGITTAL SECTION
Sagittal MR images of PCL
posterior cruciate ligament bows posteriorly In extension but is straight (taut) in flexion.
extended knee
50 degree flexed knee
MRIAxial Section
Tibial tuberosity
Saphenous nerve
Great saphenous vein
Medial gastrocnemiusLateral gastrocnemius
Soleus
TibiaTibialis anterior
Fibula
Patellar tendon
Lateral tibial condyle
Iliotibial tract
Medial tibial condyle
Sartorius tendon
Gracilis tendon
Semitendinosus tendonSemimembranosus tendon
Medial femoral condyle
Lateral femoral condyle
Infrapatellar fat pad Patellar tendon
Popliteus tendon
Sartorius muscle
Semimembranosus tendon
Semitendinosus tendon
Tibial nerve
Popliteal veinPopliteal artery
Lateral gastrocnemius
Joint capsule
Superior medial geniculate arterySuperior lateral geniculate artery
PatellaSynovial fluid
Quadriceps tendon
Semitendinosus tendonSemimembranosus muscle
Popliteal artery and vein
Biceps femoris
Femur Vastus medialis
Sartorius muscle
Suprapatellar bursa
Sagittal Section
Vastus medialis
Medial gastrocnemius
Sartorius
Vastus medialis
Medial femoral condyle
Medial meniscus
Tibia
Medialgastrocnemius
Gracilis tendon
Sartorius muscle
Vastus medialis
Medial femoral condyle
Medial meniscus
Tibia
Semitendinosus tendon
Medialgastrocnemiusmuscle
Gracilis tendon
Medial gastrocnemiustendon
Posterior horn of medial meniscus
Joint capsule
Anterior horn of medial meniscusSemimembranosustendon
Semitendinosustendon
Semimembranosusmuscle
Shaft of the tibia
Shaft of the femur
Infrapatellar fat pad
Patella
Oblique poplitealligament
Posterior cruciate ligament
Popliteus muscle
Posterior cruciateligament
Popliteal artery
Anterior cruciate ligament
Patellard tendon
Quadriceps tendon
Tibial nerve
Popliteal vein
Anterior cruciate ligament
Popliteal artery
Popliteus muscle
Posterior horn oflateral meniscus
Quadriceps tendon
Patella
Patellar tendon
Tibia
Femur
Popliteus muscle
Popliteus tendon
Posterior horn oflateral meniscus
Head of fibula
Anterior horn of lateral meniscus
Lateral femoral condyle
Commonperoneal nerve
Lateral head ofgastrocnemius muscle
Biceps femoris muscle
Tendon of the lateralhead of gastrocnemius
Common peronealnerve
Lateral meniscus
Vastus lateralis muscle
Superior tibiofibularjoint
Tibialis anterior muscle
Coronal Section
Biceps femoris tendon
Biceps femoris
Popliteal artery
Lateral head of gastrocnemius muscle
Head of fibula
Semimembranosusmuscle
Gracilis tendon
Semimembranosustendon
Medial head ofgastrocnemius muscle
Semitendinosustendon
Lateral superior geniculate artery
Sartoriusmuscle
Medial inferior geniculateartery
Popliteal artery
Popliteus muscle
Biceps femoris tendon
Lateral femoral condyleGreatsaphenousvein
Popliteus muscle
Lateral gastrocnemius tendon
Medial gastrocnemius tendon
Medial femoral condyle
Sartorius tendon
Gracilistendon
Posterior cruciate ligament
Lateral tibial plateau
Semimembranosus tendon
Medial tibial plateau
Great saphenous vein
Lateral meniscus
Head of the fibula
Anterior cruciate ligament
Lateral collateral ligament Medial collateralligament
Medial femoral condyle
Lateral femoral condyle
Popliteus tendon
Lateral intermuscularseptum
Anterior cruciate ligament
Lateral meniscus
Lateral intercondylar tubercleMedial intercondylar tubercle
Posteriorcruciate ligament
Vastus medialis muscle
Anterior cruciate ligament
Iliotibial band
Iliotibial band
Anterior horn ofmedial meniscus
Infrapatellar fat pad
Vastus lateralis tendon
Lateral retinaculum
Patella
Lateral retinaculum
Infrapatellar fat pad
Patellar tendon
Medial retinaculum
Quadriceps tendon
