MRI of the Knee:
Part 3: ligaments
Mark Anderson, M.D.
University of Virginia
Health System
Learning Objectives
• discuss the common
mechanisms and MR
appearance of isolated
injuries of each of these
ligaments.
• describe the anatomy and
function of the stabilizing
ligaments of the knee as
well as their normal
appearance on MR images.
• list the most common types of multi-ligament injuries of the knee
and the MR findings that will influence the surgical management of
these patients
• At the end of the presentation, each participant should be able to:
Lecture Outline
• Knee stability
• Single ligaments
- anatomy / pathology
- ACL / PCL
- medial stabilizers
- lateral stabilizers
• Treatment options
Knee Stability
• Stabilizers
– Static (ligaments)
– Dynamic (muscles/tendons)
Ant
Post
Valgus
Varus
• Primary motions
– Flexion / extension
– Rotation
Int Ext
• Forces (tibia)
– Ant / Post
– Varus / Valgus
– Int / Ext Rotation
Knee Stability
• Anterior ACL (90%)
• Posterior PCL (95%)
• Valgus MCL
• Varus LCL
• Ext Rotation Popliteus
MCL
• Int Rotation ACL
Ant
Post
Valgus
Varus
Int Ext
Ligamentous Restraints
Cruciate Ligaments
• Named for tibial
attachments
• Anterior (lateral)
• Posterior (medial)
A
P
ACL: normal anatomy
• Lateral notch
• Femur
• Anterior tibial plateau
A
P
A
ACL: normal anatomy
• Functional bundles
– anteromedial
• taut in flexion
– anterior drawer test
– posterolateral
• taut in extension
– Lachman test
• resists tibial rotation
– pivot shift test
Bicer EK, Knee Surg Sports Traumatol Arthrosc 2010
AM PL
AM
PL
Kopf S Knee Surg Sports Traumatol Arthrosc 2009
ACL: normal MR anatomy
• Sagittal morphology – Taut
– Parallel • intercondylar roof
(aka - Blumenstaat’s line)
• Signal intensity – Low / intermediate
– Striated • fiber geometry
Evaluate in all planes
AM
PL
PL AM
ACL: other imaging planes
• Oblique coronal
• Oblique axial
3D SPACE
ACL Injury
• Injuries
– ~80-250K / year
– ~100K reconstructions
• Mechanism
– 70% - non-contact
– twisting
• tibia planted
• ext femoral rotation
• valgus (lat impaction)
ACL: complete tear
• Primary signs
– edematous mass
– “empty notch”
– irregular, horiz contour
– focal disruption
ACL: complete tear
• Primary signs
– edematous mass
– “empty notch”
– irregular, horiz contour
– focal disruption
• Secondary signs
– bone contusions
– “deep notch”
– Segond fracture
– ant tib translation
– uncovering of PHLM
• Uncommon injury
– more common in children
– adults – often hyperextension
• Subtle findings
• Treatment
– conservative
– arthroscopic fixation
– status of ligament?
ACL: avulsion
35M 15M baseball injury
ACL: partial tear
• Ochi, Arthroscopy 2006
– 169 ACL tears
– 10% (17) partial
– AMB > PLB
• Clinical exam
– + ant drawer (flex) = AMB tear
– + Lachman (ext) = PLB tear
– minority have + exam
• Arthroscopy
– ligament may appear “normal”
• hard to assess remaining fibers
• may miss PLB tear
ACL: partial tear
• MRI
– abnormal SI with intact fibers
– absent / disrupted bundle
– secondary signs
• contusions
• ant tibial translation
67 M – knee injury
PL? AM
AM
PL
ACL: partial tear
• MR challenges
– sensitivity 40-77%
– specificity 62-89%
– partial vs. complete
• normal vs. mild partial
• high grade partial vs. complete
ACL: partial tear
• Van Dyck, Skeletal Radiol, 2011
– 172 pts
– 3T: complete vs. partial tears
– accuracy
• complete tear – 97%
• partial tear - 95%
Couldn’t tell partial vs. complete– 13%
ACL: partial tear
• Chang, Clin Orthp Relat Res, 2013
– MRI - isolated bundle tears
– Accuracy – 83%
– AMB – 91% / PLB 78%
– worse with acute tears
49F – partial tear of AMB only
• Siebold, Arthroscopy 2008
– individual bundle repair
– maintaining other bundle
• increased vascularization
• proprioception
ACL: partial tear
• Ng, Skeletal Radiol, 2013
– 61 pts
– conventional planes
– added oblique axial
– accuracy
• standard – 74%
• plus obl axial - 87%
ACL: partial tear
• 2003 Chen Acta Radiol
Importance of preserved, taut fiber(s)
• 1997 Chowdhury AJR
“Stable” (normal or low grade tearing)
“Unstable” (high grade or complete tear)
Sensitivity – 100% Specificity – 96%
• 1995 Zeiss JCAT
Lateral bone contusions
72% of patients w/complete tears vs 12% w/partial tears
80% of patients with PTs and contusions went on to CT in 6 months
ACL: partial tear
• Summary
– abnormal signal
– intact fibers
– bone contusions
– oblique axial images
– 3T
Normal
Low grade
High Grade
Complete
ACL: partial tear vs ganglion
High signal
expanding ligament “Celery stalk”
“Drumstick”
ACL Reconstruction
• Review articles
– Bencardino, Radiographics, 2009
– Meyers, AJR, 2010
– Casagranda, AJR 2009
• Surgical options
– bone / patellar tendon / bone
– hamstring (4 strand)
– allograft
– single vs double bundle
Meyers, AJR 2010 Suomalainen AJSM 2011
ACL Reconstruction
• Graft remodeling
– tendon ligament
– 1-2 mos: vascular ingrowth (periph)
– 2-10 mos: fibroblasts + vessels
– 1-3 yrs: fibroblasts + vessels
– 3 yrs: histology similar to ligament
• Affects MR appearance
– post op – homogeneous low
– heterogeneous (3-12 mos)
– 1-2 yrs – homogeneous low
Ntoulia , Skeletal Radiol 2013
ACL Reconstruction
• Tunnels (radiographs)
– femoral
• lateral view
– post cortex
– Blumensaat’s line
• AP view
– 10-11 or 1-2 o’clock (classic)
– “anatomic” – more horizontal
• skeletally immature
– “physeal sparing”
12
6
ACL Reconstruction
• Tunnels (radiographs)
– femoral
• lateral view
– post cortex
– Blumensaat’s line
• AP view
– 10-11 or 1-2 o’clock (classic)
– “anatomic” – more horizontal
• skeletally immature
– “physeal sparing”
– tibial
• lateral view
– post to Blumensaat’s line
ACL Reconstruction
• Tunnels
– femoral
• lat – post cortex/Blumensaat’s line
• AP – 10-11 or 1-2 o’clock
– tibial
• lat – post to Blumensaat’s line
– widening
• predominantly in 1st 6 months
• usually no clinical impact
ACL Reconstruction
• Tunnels
– femoral
• lat – post cortex/Blumensaat’s line
• AP – 10-11 or 1-2 o’clock
– tibial
• lat – post to Blumensaat’s line
– widening
• predominantly in 1st 6 months
• usually no clinical impact
– fluid
• small amounts normal in 1st year
• more common with hamstring graft
– cysts
• 22% - no clinical impact
• may extend into soft tissues
ACL Graft: complications
• 3% risk of failure at 2 yrs – early
• poor surgical technique
• failure of graft incorporation
• errors in rehabilitation
– late
• trauma with new tear
• Complications – tear
– impingement
– arthrofibrosis
– miscellaneous
17M prior ACL recon
ACL Reconstruction
• Tear – complete
– partial
– stretching
– most susceptible 4-8 mos
• MR findings – discontinuity
– partial disruption
– thickened
– bowed / lax appearance
• Secondary signs
• Clinical exam
17M prior ACL recon 42F
No instability on exam
17M
ACL Reconstruction
• Impingement
– intercondylar roof
• tibial tunnel – too anterior
• narrow notch / spur
– sidewall
• tibial tunnel – too lateral
– PCL
• femoral tunnel too vertical
ACL Reconstruction
• Arthrofibrosis
– disorganized fibrous tisssue
– focal (ant) / diffuse
– “cyclops lesion”
• reported incidence: 13-35%
– clinical
• loss of extension
– MR
• heterogeneous tissue (anterior)
ACL Reconstruction
• Gohil S, et al., 2013
Knee Surg Sports Traumatol Arthosc
– cyclops lesions (49 patients)
– 22 (48.6%) cyclops at one yr
– 17/22 (77%) MRI + / normal exam
• “MR cyclops”
– 5/22 (23%) MRI + / loss of extension
• “clinical cyclops” (10% of all pts)
19F rower 19F rower - asymptomatic
ACL Reconstruction
• Tear
• Impingement
• Arthrofibrosis
• Miscellaneous – infection
– patellar fracture
– hardware
• loosening
• fracture
• displacement
PCL
• 2X tensile strength of ACL
• Restricts post tibial translation
• Taut in flexion
Posterior Drawer
MRI: Normal PCL
• Arched – Homogeneous dark
• Broad origin – Medial notch
• Compact insertion – Between post horns
– Below joint line
PCL Injury
• 40% isolated PCL
• 60% with post-lat corner injury
– PCL reconstruction?
• Mechanism of injury
– Anterior blow to flexed knee
– Forced hyperflexion
PCL Injury
• MRI Findings
– abnormal signal
– discontinuity
Complete – 45%
Partial – 47%
Avulsion – 8%
18M college football recruit
Medial Stabilizers
• Anterior – MPFL
• Middle – MCL
• Posterior – Posteromedial Corner
– posterior oblique ligament
– semimembranosus
– posterior horn medial meniscus
– oblique popliteal ligament
• Medial side (3 layers)
– I superficial fascia
– II superficial MCL / MPFL
– III deep MCL (meniscus)
AM
MG
MCL
MPFL: normal anatomy
• Primary patellar stabilizer
• Anatomy
– part of medial retinaculum
– just below vastus medialis
– femoral attachment
• near adductor tubercle
• proximal aspect of MCL
revistaartroscopia.com.ar
VM
MCL
MCL: normal anatomy
• Superficial Component
• Deep Component
meniscofemoral
meniscotibial (coronary)
• Bursa
Ant
Posterior Oblique Lig: normal anatomy
• Posterior to MCL
– origin just below med gastroc
– three arms
• Capsular
• Central
– main component
– reinforces deep MCL
– attaches to PHMM
– blends with SM tendon
• Superficial
CEN
S
M
C
L
CA
MG
SM
• Multiple arms
– direct
• postero-medial tibia
– anterior
• medial aspect of tibia
• deep to superficial MCL
– capsular
– inferior
Semimembranosus: normal anatomy
LaPrade, JBJS 2008
Pes Anserine Tendons: normal anatomy
• Sartorius
• Gracilis
• Semitendinosus
S G
ST
S
G
ST
S G
ST
S
S
Medial Stability
• MPFL
– resists lateral patellar sublux
• MCL
– valgus – (flexion)
– external rotation
• POL
– valgus – (extension)
– internal rotation
• Semimembranosus
• Pes Anserine
dynamic
Medial Stability
• Anteromedial rotatory instability
– injury to multiple medial structures
• MCL (deep/superficial)
• POL
• often with ACL tear
– medial tibial plateau
• anterior subluxation
• external rotation
• medial joint space opening
Pathology: MPFL
• Lateral patellar dislocation
– impacts lateral femoral condyle
• Lateral patellar dislocation
– impacts lateral femoral condyle
• Associated injuries
– bone contusions
Pathology: MPFL
• Lateral patellar dislocation
– impacts lateral femoral condyle
• Associated injuries
– bone contusions
– cartilage injury
• patella
• femur
may be low
near wgt-bearing surface
Pathology: MPFL
• Mechanism of injury
– lateral patellar dislocation
• Associated injuries
– bone contusions
– cartilage injury
• patella
• femur
– MPFL injury
• femur
• patella
• both
Pathology: MPFL
• Mechanism of injury
• Associated injuries
– bone contusions
– MPFL injury
• femur
• patella (fx)
• both
– cartilage injury
• MPFL Reconstruction
Pathology: MPFL
Pathology: MCL
• Two mechanisms
– valgus force
• foot planted
• blow to outside of leg
– valgus + external rotation
• Proximal injuries more
common than distal
nydailynews.com
superamazing.net
Pathology: MCL
• Radiographic findings
– stress views
• > 10 mm opening
• tears
– MCL
– POL
– mensicotibial ligament
– Pelegrini-Stieda – chronic
• not always MCL
• may involve adductor magnus
Grade Clinical MRI
1 Sprain Thickened
Irregular
ST edema
MCL Injury: MRI
24F with knee pain 24F roller derby injury
Grade Clinical MRI
1 Sprain Thickened
Irregular
ST edema
2 Partial Focal SI
Tear
MCL Injury: MRI
MCL Injury: MRI
“Reverse Segond fx” Avulsion: coronary ligament
PCL and MM tears
15M baseball injury
Grade Clinical MRI
1 Sprain Thickened
Irregular
ST edema
2 Partial Focal SI
Tear
3 Complete Discontinuity
Tear
MCL Injury: MRI
• Distal tear
– poor healing
– synovial fluid leakage
– may require surgery
• “Stener lesion of the knee”
– torn fibers superficial to
pes anserine tendons
Pathology: MCL
18M injured knee playing football
• Posterior oblique ligament
– usually injured with other ligaments
• Associated injuries
– semimembranosus (70%)
– peripheral MM detachment (30%)
– both (20%)
• Treatment
– usually conservative
– unless mulitligament injury
Pathology: posteromedial corner
20M dirt bike accident
• More frequent than MCL alone
• MCL + ACL
– 7-8% lig injuries
• MCL + PCL
– <1% lig injuries
Pathology: combined injuries
59F – skiing injury
Case 7
Posterolateral Corner
• Challenging / complex anatomy
– “the dark side of the knee”
• Difficult physical exam
– 70% PLC injuries missed initially
Pacheco, JBJS 2011
• Clinical importance
– failure to diagnose or treat PLC
• unstable gait
– inherently more unstable than medial
• osteoarthritis (convex surfaces)
• early failure of cruciate grafts
• Biceps tendon
– long head / short head
• Lateral (fibular) collateral ligament
• Popliteus muscle / tendon
• Popliteofibular ligament
• Popliteomeniscal fascicles
• Fabellofibular ligament
• Arcuate ligament
• Oblique popliteal ligament
• Iliotibial band
Posterolateral Corner: what’s important?
Posterolateral Corner: overview
B
P
ITB
B
L
C
• Biceps tendon
• LCL
• Iliotibial band
• Popliteus complex
– popliteus tendon
– popliteomensical fascicles
– popliteofibular lig
Ant
back to front
“BLT”
Post
Posterolateral Corner: biceps tendon
• Long head
– direct
• fibular styloid
• conjoined attachment
– anterior
• ant to LCL – aponeurosis
• Short head
– direct
• fibular head
– anterior
• medial to LCL
• post-lat tibial plateau
Ant
B
C
Posterolateral Corner: LCL
• Lateral femoral condyle
– above popliteus notch
• Fibular head
– styloid process
– conjoined “tendon”
Ant
L
C
B
Posterolateral Corner: anterolateral lig
• History – 1879 – Segond – pearly fibrous band
– 1976 – Hughston – lat. capsular lig
– 1986 – Irvine – ant obl band of the FCL
– 1986 – Terry – anterolateral ligament
– 2000 – LaPrade – mid 1/3 lat capsular lig
– 2007 – Vieira – anterolateral ligament
– 2012 – Vincent - anterolateral ligament
LC
L
Posterolateral Corner: anterolateral lig
• Anatomy
– femoral – ant / distal to LCL
– two components
• LFC to lat meniscus + lat tibia
• site of Segond fracture
– LCL + ALL = “LCL complex”
• Ligament vs. capsular thickening
Adapted from Claes, J Anat 2013
LC
L
Posterolateral Corner: popliteus complex
• Popliteus muscle/tendon
• Popliteomeniscal fascicles
• Popliteofibular ligament
P
Posterolateral Corner: popliteus complex
• Popliteus muscle/tendon
– dynamic stabilizer
– origin
• popliteus notch
• post-lat LFC
– between LM and capsule
– posterior proximal tibia
P
Posterolateral Corner: popliteus complex
From Peduto, AJR 2008 Courtesy of K. Bohndorf
LM
• Popliteus muscle/tendon
• Popliteomeniscal fascicles
– stabilize lateral meniscus
– form popliteus hiatus
– three fascicles
• ant-inferior (floor)
• post-superior (roof)
• post-inferior
Posterolateral Corner: popliteus complex
• Popliteus muscle/tendon
• Popliteomeniscal fascicles
• Popliteofibular ligament
– distal to P-M fascicles
– fibular head (deep to LCL)
– popliteus M-T junction
– below lat inf geniculate vessels
B P
B P
P P
Posterolateral Corner: checklist
B P
Biceps
LCL
ALL
Pop tend
Fascicles
PFL
ITB
Lateral Stabilizers: MRI assessment
Coronal Axial Sagittal
Biomechanics: PLC injury
• Mechanisms
– non-contact twisting
• external tibial rotation
• extended knee
– non-contact hyperextension
– impact - anteromedial tibia
• post-lat force
baltimoresun.com
Posterolateral Corner: pathology
• PLC involved in 16% of lig injuries
• Usually with other ligs
– 87% combined injuries
• 43% - ACL
• 28% - PCL
• 16% - ACL + PCL
– 12% isolated PLC
movietvtechgeeks.com
• Isolated PLC injuries
– < 2% of all lig injuries
– 56% involve > 1 structure
– LCL + PFL most common
Posterolateral Corner: pathology
LaPrade, 2007
College wrestler – felt “pop”
Posterolateral Corner: pathology
• Radiographs
– lat widening with stress
• > 2.7 mm – isolated LCL
• > 4.0 mm – “grade III” PLC injury
– arcuate fracture
– Segond fracture
– Gerdy’s tubercle avulsion
Posterolateral Corner: pathology
• MRI Findings
– evaluate individual ligaments
– bone contusions
• ant medial femoral condyle
Posterolateral Corner: pathology
• MRI Accuracy
– ITB, biceps, LCL 90 - 95%
– popliteus tendon 85%
– popliteofibular lig 65%
LaPrade, AJSM, 2000
Theodorou, Acta Radiol 2005
• MRI: acute vs. chronic
– < 12 wks (93% detected)
– > 12 wks (26% detected)
• Multiple ligament injuries
– “knee dislocation”
– high energy trauma
– hyperextension
ACL – PCL – other
posterior capsule
popliteal artery (30%)
peroneal nerve (20-30%)
Posterolateral Corner: pathology
Posterolateral Corner: pathology
• Asociated injuries
– Arterial injury (~30%)
• 6-8 hour window
• < 8 hrs = 89% viable
• > 8 hrs = 86% amputation
– Nerve injury (20-30%)
• peroneal
• tibial
s/p knee
dislocation
• Early surgery (2-3 wks)
– better outcomes
• Reconstruction > repair
• Three critical structures
– LCL
– popliteus tendon
– popliteofibular ligament
Posterolateral Corner: treatment
Adapted from LaPrade, JBJS 2010
howtobeast.com
Posterolateral corner: treatment
34M MMA fighter: “Someone fell on my knee
and bent it backwards.”
Case 1 Findings?
20M collegiate wrestler – knee held in varus
and felt “pop” + post drawer and dial tests
INJURIES: PFL / LCL
Popliteus muscle
PCL (partial)
SURGERY:
Posterolateral corner reconstruction
Case 2
56F twisted knee while skiing
+ effusion 3+ Lachman 3+ valgus stress
discoveralta.com
INJURIES: ACL / MCL
PFL / LCL sprain
PHLM fascicles
SURGERY:
ACL reconstruction
PHLM repair (all inside)
Case 3 Findings? 32F who fell while trying to catch her
daughter. + varus stress ++Lachman
wordpress.com
INJURIES: ACL / high grade PCL
LCL / FIB avulsion
Popliteus tendon
SURGERY:
ACL reconstruction
Posterolateral corner reconstruction
Case 4 Findings? 20M presented after soccer injury
+ Lachman + varus stress
ooyala.com
INJURIES: ACL
Conjoined tendon
SURGERY: ACL reconstrustion
Posterolateral corner reconstruction
Case 5 Findings? 30M who tripped over a pumpkin
while at work
rmne.org omaha.com
INJURIES: ACL / PCL / MCL
MPFL
LM tear
SURGERY: ACL reconstruction / PCL primary repair
PLC reconstruction
MCL reconstruction
Partial lat meniscectomy
dislocation
Bonus Case Findings?
20F collegiate swimmer
with lateral knee pain
Iliotibial Band Friction Syndrome
• Athletes
– long distance runners
– lateral knee pain
• Abnormal contact
– ITB
– lateral femoral condyle
– passes over LFC with flexion
• MRI
– fluid/edema deep to ITB
– may mimic joint fluid
42F developed lateral knee pain while
training for a marathon
Posterolateral Corner: checklist
• Biceps
• LCL (ALL)
• Popliteus Complex
– tendon
– fascicles
– popliteofibular ligament
• ITB
B P
Biceps
LCL
ALL
Pop tend
Fascicles
PFL
ITB
Treatment: Single ligament
ACL
Partial?
Reconstruct 3-4 wks unless
PLC or locked knee, then
within 3 wks
Depends on imaging plus
clinical exam
PCL Isolated = controversial
Multiligament = reconstruct
MCL Usually non-surgical
Distal tear?
Post-lat Corner Surgery within 3 weeks
Repair / advance / reconstruct
PL
AM
Treatment: Multiple ligaments
ACL
PCL
MCL
Let MCL heal
Then reconstruct in 3-4 wks
ACL
PCL
Post-lat corner
Surgery within 3 weeks
Repair / advance / reconstruct
Thank You!