MRI KNEE JOINT ANATOMY

MRI KNEE JOINT ANATOMY

1. By: dr nikhil bansal resident radio-diagnosis UNDER GUIDANCE OF: DR ANAND VERMA 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) 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

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 and T2w in the sagittal plane ( meniscal, cartilage) STIR sequence in the coronal plane (marrow) T1W coronal images T2W axial images

7. General anatomy 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. ARTICULAR SURFACE Formed by – condyles of femur , patella and condyles of tibia

8. X-Ray

9. Sartorius

10. INRACAPSULAR LIGAMENTS Anterior cruciate ligament Posterior cruciate ligament Medial meniscus Lateral meniscus Transverse ligament

11. 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

12. 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

13. They measure ~3 to 5 mm in height at the periphery ~1 mm or less at the free edge.

14. MEDIAL MENISCUS 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.

15. MRI APPEARANCE ANTERIOR & POSTERIOR HORNS - Best demonstrated on sagittal view BODY of meniscus - Best seen on coronal images

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

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

18. 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

19. 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

20. 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.

21. Lateral meniscus from the periphery to the notch Normal lateral meniscus . Discoid lateral meniscus

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

23. NORMAL VARIATIONS AND PITFALLS 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%

24. Ligament of Wrisberg Ligament of Humphry

25. Popliteus Tendon 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

26. 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.

27. Transverse Ligament 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

28. Sagittal fat suppressed Medial--lateral

29. CENTRAL STRUCTURES OF KNEE

30. 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 .

31. 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.

32. 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

33. 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 .

34. ACL: Origin to insertion

35. 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.

36. AXIAL SECTION SAGITTAL SECTION

37. Sagittal MR images of PCL posterior cruciate ligament bows posteriorly In extension but is straight (taut) in flexion. extended knee 50 degree flexed knee

38. MRI Axial Section

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

40. Patellar tendon

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

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

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

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

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

46. Sagittal Section

47. Vastus medialis Medial gastrocnemius Sartorius

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

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

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

51. Shaft of the tibia Shaft of the femur

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

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

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

55. Posterior horn of lateral meniscus

56. Quadriceps tendon Patella Patellar tendon Tibia Femur

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

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

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

60. Superior tibiofibular joint Tibialis anterior muscle

61. Coronal Section

62. 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

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

64. Lateral femoral condyle Great saphenous vein Popliteus muscle

65. 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

66. Lateral meniscus Head of the fibula

67. Anterior cruciate ligament Lateral collateral ligament Medial collateral ligament

68. Medial femoral condyle Lateral femoral condyle Popliteus tendon

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

70. Vastus medialis muscle Anterior cruciate ligament

71. Iliotibial band

72. Iliotibial band

73. Anterior horn of medial meniscus

74. Infrapatellar fat pad Vastus lateralis tendon

75. Lateral retinaculum

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