MENISCAL ANATOMY ADVANCED IMAGING OF THE KNEE MENISCAL ABNORMALITIES MENISCAL FUNCTION MENISCAL FUNCTION load transmission shock absorption stability The menisci DO NOT function as primary stabilizers of the knee. Rather, when certain primary restraints are compromised, the menisci are forced to take over part of this function. RAMP LESION load transmission shock absorption stability Known association of PH MM tears / chronic ACL tears Chronic Tear of ACL Posterior horn of medial meniscus resists anterior translation of the tibia MENISCAL BLOOD SUPPLY Source: - branches of genicular vessels from perimeniscal capillary plexus (PCP) - synovial reflection adherent to meniscal surface Extent: - : 10-30% of width - lateral meniscus: 10-25% of width Concept of RED and WHITE zone WHITE ZONE RED ZONE G Bydder
MENISCAL MORPHOLOGY Medial Meniscus: Width Anterior horn 7.7mm Midportion 9.6mm Ant MENISCAL MORPHOLOGY Ant Lateral Meniscus: Width Anterior horn 10.2mm Midportion 11.6mm Posterior horn 10.6mm Posterior horn 10.6mm Post Post MENISCAL MORPHOLOGY MENISCAL MORPHOLOGY Medial Meniscus: Attachment Sites Medial Meniscus: Attachment Sites Posterior horn- Posterior horn- Posterior menis- cal root ligament Posterior menis- cal root ligament PCL PCL Root ligament Root ligament MENISCAL MORPHOLOGY Meniscofemoral lig MENISCAL MORPHOLOGY Transverse meniscal lig Medial Meniscus: Attachment Sites Medial Meniscus: Attachment Sites Anterior meniscal root lig Midportion- Anterior horn- Medial capsular ligament Transverse menis- cal ligament ACL Anterior meniscal root ligament Meniscotibial lig
MENISCAL MORPHOLOGY Popliteomeniscal Ligaments Lateral Meniscus: Attachment Sites Lateral Meniscus: Attachment Sites Meniscal root lig Posterior horn- Posterior meniscal root ligament Meniscal root lig Posterior horn- Posterior meniscal root ligament Meniscofemoral ligaments Meniscofemoral ligaments Popliteus t Popliteomeniscal ligaments Popliteus t Popliteomeniscal ligaments Popliteomen ligs Meniscofem lig Popliteomen ligs Meniscofem lig MENISCAL MORPHOLOGY Lateral Meniscus: Attachment Sites Lateral Meniscus: Attachment Sites Meniscal root lig Posterior horn- Posterior meniscal root ligament Midportion - Mid-lateral capsular ligament Meniscofemoral ligaments Popliteus t Popliteomeniscal ligaments Popliteomen ligs Meniscofem lig MENISCAL MORPHOLOGY MENISCAL MORPHOLOGY Transverse men lig Ant men root lig Lateral Meniscus: Attachment Sites Anterior horn - Transverse meniscal ligament Transverse men lig Ant men root lig Lateral Meniscus: Attachment Sites Anterior horn - Transverse meniscal ligament Anterior meniscal root ligament Anterior meniscal root ligament ACL ACL
MENISCAL MORPHOLOGY MENISCAL MORPHOLOGY Circumferential (longitudinal) fibers Radial (tie) fibers Types of force: Compression Shear Tension Distraction Compression Longitudinal Vertical Tear Compression Longitudinal Vertical Tear The longer the vertical tear, the greater the number of radial (tie) fibers that are violated and the more likely that central displacement of the inner portion of the meniscus will occur Compression Meniscal Contusion?
Shear Longitudinal Horizontal Tear Shear Longitudinal Horizontal Tear The longer the horizontal tear, the greater the number of radial (tie) fibers that are violated and the more likely that a vertical component to the tear and a multidirectional tear will result Shear Shear Central Cavitation Longitudinal Horizontal Tear Radial Tear Shear Distraction Meniscofemoral lig Tibial collateral lig Joint capsule Meniscotibial lig Radial Tear Meniscocapsular Separation, Corner Meniscal Tear, MCL Injury
Distraction Distraction Meniscocapsular Separation, Corner Meniscal Tear, MCL Injury Meniscocapsular Separation, Corner Meniscal Tear, MCL Injury Distraction MENISCAL TEARS: ROLE OF MR IMAGING What the radiologist s report should include: Location of tear Shape / length of tear Partial vs complete nature of tear Stability vs instability of tear Associated abnormalities Meniscocapsular Separation, Corner Meniscal Tear, MCL Injury MENISCAL TEARS: MR IMAGING CRITERIA MENISCAL TEARS: MR IMAGING CRITERIA Abnormality of meniscal contour Abnormality of meniscal signal Abnormality of meniscal contour Abnormality of meniscal signal Grade 1,2 = NO TEAR Grade 3 = TEAR
Grade 3 Signal Exception If seen on single image 50% of medial menisci torn 30% of lateral menisci torn Associated with radial and parrot-beak tears meniscus within a meniscus Tall Meniscus Exception meniscus within a meniscus Meniscus with an associated meniscal cyst The length of a longitudinal vertical tear relates to its anteroposterior dimension
ACL tear and longitudinal vertical tear, lateral meniscus Longitudinal vertical tears often tilt slightly. In these cases, they may simulate horizontal tears in some images. Longitudinal vertical tears often have small horizontal components : oblique
: oblique The length of a longitudinal horizontal tear relates to its anteroposterior dimension; the width relates to its centroperipheral dimension
PD FSE MR@ PD FS FSE MR@ T1 FS MR@ T.Peduto, Sydney, Australia : oblique radial Absent or Empty Meniscus The length of a radial tear relates to its centroperipheral dimension
- Lateral > - Lack of resistance to hoop stress - Unique MR imaging findings Normal Radial Tear Pseudo bucket-handle tear : oblique : oblique ABC Designated the marching cleft sign, which is also apparent when the imaging plane is oblique to a standard radial tear Harper KW, et al: AJR 185:1429,2005 A B C Marching cleft sign
Normal ANTERIOR LOWER HALF INFERIOR SURFACE POSTERIOR ABSENT MENISCUS NEXT TO PCL Normal POSTERIOR INFERIOR SURFACE MENISCAL CORE ROOT LIGAMENT ANTERIOR free-edge tears: LOWER HALF INFERIOR SURFACE POSTERIOR MENISCAL CORE POSTERIOR INFERIOR SURFACE ROOT LIGAMENT free-edge tears: free-edge tears:
Additional Types of Meniscal Tears Medial meniscus: Anterior root ligament Meniscal root lesions Medial Lateral Medial meniscus: Posterior root ligament Lateral meniscus: Anterior root ligament Lateral meniscus: Posterior root ligament Abnormalities, PRL, Normal root ligament:
Abnormalities, PRL, Abnormalities, PRL, Root ligament degeneration: Root ligament delamination associated with adjacent meniscal tears: LONGITUDINAL VERTICAL TEAR LONGITUDINAL HORIZONTAL TEAR Abnormalities, PRL, Abnormalities, PRL, Subligamentous ganglion cysts: Partial avulsion of the root ligament: LONGITUDINAL VERTICAL TEAR LONGITUDINAL VERTICAL TEAR Abnormalities, PRL, Complete avulsion of the root ligament: Abnormalities, PRL, Complete avulsion of the root ligament: LONGITUDINAL VERTICAL TEAR LONGITUDINAL VERTICAL TEAR
Abnormalities, PRL, Abnormalities, PRL, Complete avulsion of the root ligament: Meniscal root ligament avulsion Radial tear of meniscus Complete avulsion of the root ligament: Differential diagnosis: Association with SONK: LONGITUDINAL VERTICAL TEAR LONGITUDINAL VERTICAL TEAR Nodular posterior horn of meniscus Smooth posterior horn of meniscus Engelsohn E,et al: Skel Radiol 36:73,2007 Abnormalities, PRL, Abnormalities, PRL, Complete avulsion of the root ligament: Complete avulsion of the root ligament: Association with meniscal ossicle: Association with meniscal ossicle: LONGITUDINAL VERTICAL TEAR LONGITUDINAL VERTICAL TEAR Abnormalities, PRL, Additional Types of Meniscal Tears Complete avulsion of the root ligament: Association with meniscal flounce: LONGITUDINAL VERTICAL TEAR Meniscal root lesions Popliteomeniscal ligament lesions 1. Anteroinferior 2. Posterosuperior 3. Posteroinferior 4. Popliteocruciate
PS-PMFPMF AI-PMF PI-PMF Additional Types of Meniscal Tears Lateral PI-PMF PI-PMF PI-PMF This type of lesion is associated with ACL injury Medial Meniscoligamentous lesions associated with ACL tears: Posterior horn, lateral meniscus Meniscoligamentous lesions associated with ACL tears: Posterior horn, lateral meniscus FEMUR MF lig Posterior root ligament Lateral Meniscus Posterosuperior PMF One Year Later Anteroinf PMF Meniscoligamentous lesions associated with ACL tears: Posterior horn, lateral meniscus Meniscoligamentous lesions associated with ACL tears: Posterior horn, lateral meniscus Rotational instability: - When lateral meniscus remains in place, posterior root ligament avulsion and/or radial tear of posterior horn may occur Rotational instability: - When lateral meniscus translates forward, meniscal avulsions related to PM fascicles and/or meniscofemoral ligaments may occur
Meniscoligamentous lesions associated with ACL tears: Posterior horn, lateral meniscus Rotational instability: - When lateral meniscus translates forward, meniscal avulsions related to PM fascicles and/or meniscofemoral ligaments may occur More Central Wrisberg Rip Displaced Meniscal Tears : bucket handle : flap : parrot - beak More Lateral Bucket - Handle Tear: Classic Features Displaced Meniscal Tears : bucket handle : flap : parrot - beak Peripheral rim of meniscal tissue Centrally displaced meniscal tissue Continuity of anterior and posterior horns with displaced meniscal tissue Bucket - Handle Tear: Classic Features Bucket - Handle Tear: Classic Features Pericruciate meniscal tissue Double PCL Sign Bucket handle tear,
Bucket - Handle Tear: Classic Features Pericruciate meniscal tissue Pseudo-torn ACL Sign Bucket Handle Tear versus Meniscal Root Ligament Most anterior Central Normal meniscal root ligament Most posterior Bucket - Handle Tear: Condylar Entrapment Bucket - Handle Tear: Condylar Entrapment Concept: Progressive inversion of displaced fragment Peripheral portion rotates up; central portion rotates down Associated with tears of the ACL Bucket - Handle Tear: Condylar Entrapment Bucket - Handle Tear: Condylar Entrapment Deformity / thickening at junctional sites Deformity / thickening at junctional sites
Bucket - Handle Tear: Jack and Jill Lesions Bucket - Handle Tear: Patterns of Subsequent Meniscal Failure Peripheral Medial Medial Lateral Central Shear forces placed on both central / peripheral portions Lateral Central failure Peripheral (rim) failure Broken handle Radial / horizontal tear, meniscocapsular separation Leaking bucket Bucket - Handle Tear: Broken Handle Bucket - Handle Tear: Rim Tear tear in peripheral anterior > posterior rim Bucket - Handle Tear: Rim Tear Bucket - Handle Tear: Double Bucket - Handle Tear tear in peripheral anterior > posterior rim Displacement +/- inversion of involved meniscal rim
Bucket - Handle Tear: Treatment Bucket - Handle Tear: Flipped Meniscus Resect displaced meniscal tissue Reattach meniscal tissue Signs of Reparability rim width < 4mm tear length > 9mm normal signal of inner fragment Capsular detachment of posterior > anterior horn of lateral > Displacement and inversion of involved meniscal horn Bucket - Handle Tear: Flipped Meniscus Displaced Meniscal Tears : bucket handle : flap : parrot - beak POSTERIOR HORN OF LATERAL MENISCUS IS DISPLACED ANTERIORLY ANTERIOR HORN OF MEDIAL MENISCUS IS DISPLACED POSTERIORLY Displaced Meniscal Tears Displaced Meniscal Tears : bucket handle : flap : parrot - beak : bucket handle : flap : parrot - beak
Displaced Meniscal Tears Displaced Meniscal Tears : bucket handle : flap : parrot - beak : bucket handle : flap : parrot - beak Differential diagnosis: Anterior arm, SM tendon UNSTABLE MENISCAL TEARS Defined as a tear in which the meniscus or a meniscal fragment is displaced or can be displaced by a probe Characteristics of Unstable Tear A tear that on inspection or probing is greater than 9mm in length Characteristics of Unstable Tear A tear that on inspection or probing has multiple directions Radial / horizontal tears
Characteristics of Unstable Tear A large radial tear or a radial tear with wide separation at the site of tear Characteristics of Unstable Tear A gap at the site of tear that may collect fluid IS A MENISCAL TEAR THE CAUSE OF THE PATIENT S SYMPTOMS?, vertical longitudinal, or complex > horizontal or oblique tears Unstable > stable tears Associated marrow edema or ligamentous abnormalities ANATOMIC STRUCTURES PHYSIOLOGIC EFFECTS MR IMAGING EFFECTS PATHOLOGIC CONDITIONS POSTOPERATIVE MENISCUS Zanetti M,et al: AJR 181: 635, 2003 ANATOMIC STRUCTURES Popliteus Tendon Sheath / Fascicles Meniscomeniscal ligaments anterior transverse meniscal ligament (60%) posterior transverse meniscal ligament (4%) oblique meniscomeniscal ligament (4%)
Meniscomeniscal Ligaments Meniscomeniscal Ligaments anterior transverse meniscal ligament (60%) posterior transverse meniscal ligament (4%) oblique meniscomeniscal ligament (4%) anterior transverse meniscal ligament (60%) posterior transverse meniscal ligament (4%) oblique meniscomeniscal ligament (4%) Meniscomeniscal ligaments Meniscomeniscal ligaments anterior transverse meniscal ligament (60%) posterior transverse meniscal ligament (4%) oblique meniscomeniscal ligament (4%) anterior transverse meniscal ligament (60%) posterior transverse meniscal ligament (4%) oblique meniscomeniscal ligament (4%) M L Meniscomeniscal ligaments ANATOMIC STRUCTURES Meniscofemoral Ligaments anterior transverse meniscal ligament (60%) posterior transverse meniscal ligament (4%) oblique meniscomeniscal ligament (4%) Ligament of Humphry
ANATOMIC STRUCTURES Meniscal / Ligament Anomalies ANATOMIC STRUCTURES Meniscal / Ligament Anomalies Beware of branching lateral meniscus Beware of branching lateral meniscus Transverse ligament Anterior root ligament Anterior Root, Lat Meniscus / Transverse Ligament ANATOMIC STRUCTURES ANATOMIC STRUCTURES Meniscal Recesses Simulates bucket-handle tear Posterior Root Ligament, Lateral Meniscus ANATOMIC STRUCTURES PHYSIOLOGIC EFFECTS MR IMAGING EFFECTS PATHOLOGIC CONDITIONS POSTOPERATIVE MENISCUS PHYSIOLOGIC EFFECTS Meniscal Flounce Meniscal Flounce
PHYSIOLOGIC EFFECTS Meniscal Tear Meniscal Flounce Abnormal Meniscal Flounce ANATOMIC STRUCTURES PHYSIOLOGIC EFFECTS MR IMAGING EFFECTS PATHOLOGIC CONDITIONS POSTOPERATIVE MENISCUS PATHOLOGIC CONDITIONS Vacuum Phenomenon CPPD Crystal Deposits ADVANCED IMAGING OF THE KNEE MENISCAL ABNORMALITIES