MRI of the Knee:

Part 3: ligaments

Mark Anderson, M.D.

University of Virginia

Health System

Learning Objectives

• discuss the commonmechanisms 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

IntExt

• 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

IntExt

Ligamentous Restraints

Cruciate Ligaments

• Named for tibial

attachments

• Anterior (lateral)

• Posterior (medial)A

P

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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

AMPL

AMPL

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

PLAM

ACL: other imaging planes

• Oblique coronal

• Oblique axial

3D SPACE

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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

35M15M 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

25

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%

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ACL: partial tear

• 2003 Chen Acta RadiolImportance 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 JCATLateral bone contusions 72% of patients w/complete tears vs 12% w/partial tears80% 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 2010Suomalainen 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

27

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 recon42F

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

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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., 2013Knee 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 rower19F 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

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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 Componentmeniscofemoral

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

MCL

CA

MG

SM

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• 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

SG

ST

S

G

ST

SG

ST

S

S

Medial Stability

• MPFL– resists lateral patellar sublux

• MCL– valgus – (flexion)

– external rotation

• POL– valgus – (extension)

– internal rotation

• Semimembranosus

• Pes Anserinedynamic

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

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• 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

• femurmay 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

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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 ThickenedIrregularST edema

MCL Injury: MRI

24F with knee pain24F roller derby injury

Grade Clinical MRI

1 Sprain ThickenedIrregularST edema

2 Partial Focal SITear

MCL Injury: MRI

MCL Injury: MRI“Reverse Segond fx” Avulsion: coronary ligament

PCL and MM tears

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15M baseball injury

Grade Clinical MRI

1 Sprain ThickenedIrregularST edema

2 Partial Focal SITear

3 Complete DiscontinuityTear

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: MCL18M 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

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• 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 initiallyPacheco, 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

BP

ITBB

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

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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

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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

BP

BP

PP

Posterolateral Corner: checklist

BP

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

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• 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

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• Early surgery (2-3 wks)

– better outcomes

• Reconstruction > repair

• Three critical structures

– LCL

– popliteus tendon

– popliteofibular ligament

Posterolateral Corner: treatment

Adapted from LaPrade, JBJS 2010howtobeast.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 varusand felt “pop” + post drawer and dial tests INJURIES:

PFL / LCLPopliteus musclePCL (partial)

SURGERY:

Posterolateral corner reconstruction

Case 2 56F twisted knee while skiing

+ effusion 3+ Lachman 3+ valgus stress

discoveralta.com

INJURIES:ACL / MCLPFL / LCL sprainPHLM fascicles

SURGERY:

ACL reconstructionPHLM repair (all inside)

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Case 3 Findings?32F who fell while trying to catch her daughter. + varus stress ++Lachman

wordpress.com

INJURIES:ACL / high grade PCL LCL / FIB avulsionPopliteus tendon

SURGERY:

ACL reconstructionPosterolateral corner reconstruction

Case 4 Findings?20M presented after soccer injury+ Lachman + varus stress

ooyala.com

INJURIES:ACLConjoined tendon

SURGERY:ACL reconstrustionPosterolateral corner reconstruction

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Case 5 Findings?30M who tripped over a pumpkinwhile at work

rmne.orgomaha.com

INJURIES:ACL / PCL / MCLMPFLLM tear

SURGERY:ACL reconstruction / PCL primary repairPLC reconstructionMCL reconstructionPartial 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

BP

Biceps

LCL

ALL

Pop tend

Fascicles

PFL

ITB

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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!

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