The document summarizes the radiological anatomy of the knee joint. It describes the various ligaments, tendons, bones and cartilage that make up the knee, including the medial and lateral menisci, anterior and posterior cruciate ligaments, patellar tendon, and surrounding muscles. It provides imaging protocols for MRI of the knee, covering positioning, slice thickness, pulse sequences and imaging planes used to visualize the different knee structures. Common anatomical variations and pitfalls in interpretation are also discussed.

1. BY: DR NIKHIL BANSAL
RESIDENTRADIO-DIAGNOSIS
UNDERGUIDANCEOF:
DR ANANDVERMA
HOD(RADIO-DIAGNOSIS)
MGMC&H
RADIOLOGICAL
ANATOMY OF KNEE JOINT

2. 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 likely 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 affected by traumatic and
degenerative conditions

3. 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

4. Patient Positioning
 Supine, with the leg in full extension.
 The knee is placed in 10 to 15° of external rotation(esp for
sagittal image)
SliceThickness
 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

5. 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.

6. Knee protocol
 Fast spin echo PD andT2w in the sagittal plane
(meniscal, cartilage)
 STIR sequence in the coronal plane(marrow)
 T1W coronal images
 T2W axial images

7. Generalanatomy
 Knee is the largest and more complex joint of the body
 Complexity is the result of fusion of three joint
- lateral tibiofemoral joint
- medial tibiofemoral joint
- femoropatellar joint
 It is a compound synovial joint ,incorporating two condylar
joints between condyles of femur and tibia and one saddle
joint between femur and patella.
ARTICULARSURFACE
 Formed by – condyles of femur , patella and condyles of
tibia

8. X-Ray

14. Sartorius

22. INRACAPSULAR LIGAMENTS
1. Anterior cruciate ligament
2. Posterior cruciate ligament
3. Medial meniscus
4. Lateral meniscus
5. Transverse ligament

23. Menisci:
 The menisci of the knee are two semilunar,
C-shaped fibrocartilaginous disks that sit
on the peripheral margins of tibial plateau
 Upper surfaces of both menisci are concave,
and they articulate with the convex femoral
condyles.
 Each meniscus has two ends which are
attached to tibia, and two borders

24. (a) The outer border is thick , convex and
fixed to the fibrous capsule
(b) Inner border is thin concave and free.
Micro-anatomy: Type 1 Collagen
Red Zone: 1/3
White Zone: 2/3

25. Theymeasure ~3to5mm in heightattheperiphery
~1mm orlessatthefreeedge.

26. MEDIALMENISCUS
 Medial meniscus is shaped more like a half -
circle.(open “C”)
 The width of the medial meniscus, in contrast to
the lateral meniscus, gradually tapers from
posterior(12mm) to anterior(6mm)
 Peripheral margin of the medial meniscus is more
firmly attached to the tibial collateral ligament.

27. MRIAPPEARANCE
ANTERIOR &POSTERIORHORNS
- Best demonstrated on sagittal view
BODY of meniscus
- Best seen on coronal images

28. Lateralmeniscus
 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 popliteal tendon crosses it, and more
posteriorly and centrally near the central
attachment site, where the capsule does not
extend anteriorly into the joint.

29. Anterior hornoflateralmeniscus
 The anterior and posterior horns of the lateral
meniscus are about equal in size
 Anterosuperiorly transverse ligament is
attached to it.

30. Posteriorhornoflateralmeniscus
 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

31. DiscoidMeniscus
 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

32.  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.

33. Lateralmeniscusfromtheperipherytothenotch
Normal lateral
meniscus.
Discoid lateral meniscus

34. Pitfalls…
 The posterior horns are seen
on coronal views as flat
bands that should not be
confused with discoid
menisci

35. NORMALVARIATIONSANDPITFALLS
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%

36. Ligament of
Wrisberg Ligament of Humphry

37. PopliteusTendon
 Popliteus tendon and its hiatus separate the
lateral meniscus from the joint capsule.
 Signal intensity from the popliteus tendon
sheath or fluid within its hiatus could be
mistaken for a meniscal tear on both
sagittal and coronal images

38.  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.

39. TransverseLigament
 Connects the anterior horns of both menisci
 The signal intensity produced from the loose
connective tissue between the transverse
ligament 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 ligament through the
infrapatellar fat pad on more central MR
imaging sections

40. Sagittal fat suppressed
Medial--lateral

41. CENTRAL STRUCTURES OF KNEE

42. AnteriorCruciateLigament
 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.

44.  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.

45. MRIAppearance
 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

46. Coronalimage
 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.

47. ACL:Origintoinsertion

48. PosteriorCruciateLigament
 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.

49. AXIAL SECTION SAGITTAL SECTION

50. SagittalMRimagesofPCL
posterior cruciate ligament bows posteriorly
In extension but is straight (taut) in flexion.
extended knee 50 degree flexed knee

54. MRI
Axial Section

55. Tibial tuberosity
Saphenous nerve
Great saphenous vein
Medial gastrocnemius
Lateral gastrocnemius
Soleus
Tibia
Tibialis anterior
Fibula

57. Patellar tendon

63. Lateral tibial condyle
Iliotibial tract
Medial tibial condyle
Sartorius tendon
Gracilis tendon
Semitendinosus tendon
Semimembranosus tendon

68. Medial femoral condyle
Lateral femoral condyle
Infrapatellar fat pad Patellar tendon
Popliteus tendon

71. Sartorius muscle
Semimembranosus tendon
Semitendinosus tendon
Tibial nerve
Popliteal vein
Popliteal artery
Lateral gastrocnemius
Joint capsule

76. Superior medial geniculate artery
Superior lateral geniculate artery
Patella
Synovial fluid

78. Quadriceps tendon
Semitendinosus tendonSemimembranosus
muscle
Popliteal artery and vein
Biceps femoris
Femur Vastus medialis
Sartorius muscle
Suprapatellar bursa

79. Sagittal Section

80. Vastus medialis
Medial gastrocnemius
Sartorius

81. Vastus medialis
Medial femoral condyle
Medial meniscus
Tibia
Medial
gastrocnemius
Gracilis tendon
Sartorius muscle

82. Vastus medialis
Medial femoral condyle
Medial meniscus
Tibia
Semitendinosus tendon
Medial
gastrocnemius
muscle
Gracilis tendon
Medial gastrocnemius
tendon

83. Posterior horn of medial meniscus
Joint capsule
Anterior horn of medial meniscus
Semimembranosus
tendon
Semitendinosus
tendon
Semimembranosus
muscle

87. Shaft of the tibia
Shaft of the femur

89. Infrapatellar fat pad
Patella
Oblique popliteal
ligament
Posterior cruciate ligament
Popliteus muscle

90. Posterior cruciate
ligament
Popliteal artery
Anterior cruciate ligament
Patellard tendon
Quadriceps tendon

91. Tibial nerve
Popliteal vein
Anterior cruciate ligament
Popliteal
artery
Popliteus muscle

92. Posterior horn of
lateral meniscus

93. Quadriceps tendon
Patella
Patellar tendon
Tibia
Femur

95. Popliteus muscle
Popliteus tendon
Posterior horn of
lateral meniscus
Head of fibula
Anterior horn of lateral meniscus
Lateral femoral condyle

96. Common
peroneal nerve
Lateral head of
gastrocnemius muscle
Biceps femoris muscle

97. Tendon of the lateral
head of gastrocnemius
Common peroneal
nerve
Lateral meniscus
Vastus lateralis muscle

98. Superior tibiofibular
joint
Tibialis anterior muscle

102. Coronal Section

103. Biceps femoris tendon
Biceps femoris
Popliteal artery
Lateral head of
gastrocnemius muscle
Head of fibula
Semimembranosus
muscle
Gracilis
tendon
Semimembranosus
tendon
Medial head of
gastrocnemius
muscle
Semitendinosus
tendon

104. Lateral superior geniculate artery
Sartorius
muscle
Medial inferior geniculate
artery
Popliteal artery
Popliteus muscle
Biceps femoris tendon

105. Lateral femoral condyle
Great
saphenous
vein
Popliteus muscle

106. Lateral gastrocnemius tendon
Medial
gastrocnemius
tendon
Medial
femoral
condyle
Sartorius
tendon
Gracilis
tendon
Posterior cruciate ligament
Lateral tibial plateau
Semimembranosus
tendon
Medial tibial plateau
Great
saphenous
vein

107. Lateral meniscus
Head of the fibula

108. Anterior cruciate ligament
Lateral collateral ligament Medial collateral
ligament

109. Medial femoral
condyle
Lateral femoral condyle
Popliteus tendon

110. Lateral
intermuscular
septum
Anterior cruciate ligament
Lateral meniscus
Lateral intercondylar tubercle
Medial intercondylar tubercle
Posterior
cruciate
ligament

111. Vastus medialis muscle
Anterior cruciate ligament

112. Iliotibial band

114. Iliotibial band

115. Anterior horn of
medial meniscus

116. Infrapatellar fat pad
Vastus lateralis tendon

119. Lateral retinaculum

120. Patella
Lateral retinaculum
Infrapatellar fat pad
Patellar tendon
Medial retinaculum
Quadriceps tendon