Last Updated: July 19, 2006
Anatomy: Click here
General points: Most common: posterior horn of MM
Usually does not heal on itself as there is general lack of blood supply.
Etiological classification:
Traumatic: twisting, blow, squatting,
Degenerative
Clinical features:
Pain at the sides of the knee, improves with rest
Sweeling is not much
Locked in bent position
MRI features:
T1, PD and GRE are more sensitive than T2 in the diagnosis of degeneration or tear.
T2* GRE is extremely sensitive.
FSE is not very useful due to ghost artefacts and increase in magnetization transfer.
MR grading:
Grade 1: non-articular, intrasubstance, focal or globular. Corresponds to early mucinous degeneration
Grade 2: horizontal, intrasubstance, does not involve articular surface. Corresponds to more extensive mucoid degeneration. Usually asymtomatic. Most commonly occurs in posterior horn of medial meniscus
Grade 3: extends to at least one articular surface. Corresponds to fibrocartilageneous seperation or tear. Up to 5% of grade 3 are closed and missed on orthoscopy (false negative).
Classification:
Cross sectional pattern as seen on MR sagittal imaging:
Vertical - perpendicular to the meniscal orientation
Horizontal - parellel to the meniscal orientation With or without secondary tear planes
Circumferential or surface pattern as seen on orthoscopy:
Longitudinal - parallel to/circumferential along the AP plane of meniscus as seen on CS imaging
Radial (transverse) - perpendicular to the plane of meniscus as seen on CS imaging
Oblique (flap)
Correlation between MRI and orthoscopic classification:
Vertical tears of MRI can be longitudinal, radial or oblique on orthoscopy; Horizontal tears can be longitudinal or oblique.
Complex tears display combinations. Vertical longitudinal tears are further divided into single vertical longitudinal tear, double and triple vertical longitudinal tears, displaced bucket handle tears, broken bucket handle tears.
Meniscal calcification = chondrocalcinosis:
Susceptibility artefact on T2*
May produce false grade 2/3 signal
Medial Meniscus (MM):
Tears usually start on inferior surface of posterior horn
Bucket handle tears more common
Lateral meniscus (LM):
More prone to transverse or oblique tears More prone for radial tears in the mid portion, due to more circular shape, smaller radius, increased mobility and excessive loading
MR accuracy:
Sensitivity: 80-100%
Negative predictive value: 100%
Overall accuracy: 90-95%
Orthoscopic correlation: 90%
References:
1. Stoller DW. MRI in orthopaedics & sports medicine; Second edition; 1997. Chapter 7: the knee. Lippincott Williams & Wilkins.
2. Vande Berg BC et al. Meniscal Tears with Fragments Displaced in Notch and Recesses of Knee: MR Imaging with Arthroscopic Comparison. Radiology 2005;234:842-850
