1. MR Imaging of the knee
Dr.Ajai Perti MD.
Chief Radiologist & Medical Director
Vita Diagnostics Ltd.
MR & CT Imaging Centers,
Cochin, Thrissur, Vaikom,Calicut

3. Knee pathology
• Meniscal pathology
• Ligament injury
• Cartilage lesions
• Bony and tendinous lesions.

4. Technique
• Dedicated extremity coil
• Small FOV – 18 cm
• 4mm slices / 1mm gap
• 224 x 256 matrix
• Sequences : coronal T2*, STIR, sagittal T1, T2, T2*, axial
T2 ; optional PD / T1 3D GRE fat sat.

5. Meniscal anatomy

6. Lateral meniscus Medial meniscus

7. Grading of meniscal signal
Grade I : Globular intrasubstance increased
signal intensity, not extending to
articular surface.
Grade II : Linear , may communicate with
capsular margin.
Grade III : Sharp linear, extending to articular
surface

8. Grade I
Grade II
Grade III

10. Meniscal tear
• Horizontal
• Vertical
- Radial
- Longitudinal
- Oblique
• Complex

12. Radial tear

13. Radial tear at
meniscal root

14. Radial tear at
meniscal root

16. Longitudinal tear

18. Complex tear

19. Bucket handle tear

20. Anterior flipped horn

21. Discoid meniscus
• Dysplastic; Disc like configuration
• Commonly affects lateral meniscus
• Imaging:
- Radial diameter >12mm
- Visualised in 3 or more sag. Slices
- Loss of tapering

22. Discoid lateral meniscus

23. Parameniscal cyst

24. Pseudo meniscal tears

25. MR imaging accuracy
Sensitivity Specificity
Neg.pred.
value
Medial
meniscal tear 93-98% 84-91% >95%
Lateral
meniscal tear 80-96% 91-99% >95%

26. Normal ACL

27. ACL avulsion

28. Mid substance tear

29. Proximal ACL tear

30. Interstitial tear

31. Chronic ACL tear

33. Cartilage erosions
in ACL tear

34. ACL ganglion cyst

35. Tibial tunnel determines
impingement
Femoral tunnel determines
isometry

37. Normal PCL
PCL injury
• Less common – 5-20%
• Associated with other injuries

38. Partial PCL tear Complete PCL tear

39. PCL avulsion

40. MCL injury
Grade I : Edema & hemorrhage superficial to lig.
Grade II : Displacement of lig. fibres from bone
Grade III : Complete lig. discontinuity.

41. Grade II
Grade I
Grade III

42. LCL tear

43. Posterolateral corner injury ……

44. O’Donoghue’s triad

45. MR imaging accuracy
Sensitivity Specificity
ACL tear 95-98% 73-88%
PCL tear 97-99% 80-95%

46. Tendon tears

47. Chondromalacia patella
• Softening of articular cartilage
• Common in young adults, can mimic meniscal tear
• Predisposing – Trauma, patellar malalignment,
subluxation , PCL injury etc.

49. • Primarily affects male patients -
10 to 20 yrs
• Typically involves the lateral
surface of med.fem.condyle.
• H/o trauma in 50%
Osteochondritis dissecans

50. Osteochondritis dissecans - Staging
Stage I : lesion 1-3cm ; intact cartilage
Stage II : Cartilage defect ; no loose body
Stage III : Partially detached ost.chond fragment
Stage IV : Complete separation ; loose body +

52. Spontaneous osteonecrosis
• Older females , acute medial joint pain
• Subchondral sclerotic focus with marrow
edema, often involving med.femoral condyle

54. Tibial stress fracture

55. Menisceal tears-a dilemma

56. • Grade-2 vs grade 3 signals –
• To distinguish articular surface extension of
the tears.
• Intrasubstance tear –at scopy - may need
probing.
• Effusion- If present – disrupted menisceal
surface.

57. Contd….
• Transverse ligament-
• Anterior horns of medial & lateral
meniscus.
• Antero-lateral to LM - between tibial
attachment of ACL and Infra patellar fat
pad.
• Seen in 40% pts.
• Simulates an oblique tear of LM.

58. contd….
• Fibrillation- Fraying of the free edge.
• Use fat sat images.
• FrayingMacerationImbibes synovial
fluidHigh signal on T2WIMimics a
tear.

59. cont…
• Popliteus tendon-
• Sheath near the Posterior horn of LM 
Grade-3 signal  Tear.
• After lat. meniscectomy Popliteus
Retained post.horn remnant.

60. contd. …
• Menisco-Femoral Ligaments-Anterior -Lig.
Of Humphrey- ant. to PCL-34%.
• Posterior -Lig. Of Wrisberg- post. to PCL-
60%.
• Fat bet. Post horn of LM and MF ligament
Mimics vertical tear in post.horn of LM.

61. Pseudo bucket-handle tear….
• Separate portions of PHLM-In corona
sections.
• Not seen with Medial meniscus.
• Look at Sagittal images.

62. Lax meniscal sign….
• Lax or redundant meniscus- MM with
asso. EffusionMimics menisceal tear.
• Disappears with joint manipulation.

63. Others…..
• Vaccum Phenomenon-Intra-articular
gas Signal void Mimics tear.
• Pesudo loose body-Intercondylar notch
Low signalMimics a loose body.
• MCL bursa- bet. MM and MCL 
Menisco-capsular tear.

64. Final Request….
• What the mind doesn’t know the eyes…….
• Radiologists do make mistakes even after
years of MR interpretation….
• Follow ups are of great help to improve the
diagnostic accuracy…..!!!!

66. Thank you for your patience…..