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Injuries of the Knee JointAndrew Bonett
M.S.M.S. AnatomyUniversity of South Florida
July 16, 2009
Gross Anatomy: Bones
patellar surface
intercondylar eminence
Gross Anatomy: Skeletal Structure
22
Gross Anatomy: Articular Surfaces
Gross Anatomy: Menisci Fibrocartilaginous structures
Attach to tibia in intercondylar
region
Transverse ligament connects
the anterior horns of each menisci
Vascular periphery (2-3 mm)
Medial meniscus
Oval-shaped
Attached to MCL
Thinner , less mobile
Lateral meniscus
Circular
Thicker, more mobile
Gross Anatomy: Synovial Membrane
MM
PCL
ACL
LM
Does not invest cruciate ligaments!
Bursae:
•Suprapatellar
•Subpopliteal
•Prepatellar
•Subcutaneous
infrapatellar
•Deep infrapatellar
Gross Anatomy: LigamentsMedial Collateral
(MCL)Lateral Collateral
(LCL)Anterior Cruciate
(ACL)Posterior Cruciate
(PCL)Meniscofemoral
(MFL)
Meniscofemoralligament
Gross Anatomy: MusclesThigh
Quadriceps femoris – VL, VM, VI, RFSartoriusGracilisHamstrings – BF, SM, ST IT band – GM, TFL
LegGastrocnemiusPlantarisPopliteus
(Pes anserinus)
Gross Anatomy: Popliteal Fossa
1. Semitendinosus
2. Biceps femoris
3. Semimembranosus
4. Sciatic nerve
5. Popliteal vein
6. Popliteal artery
Tibial n. Common peroneal n.
Gross Anatomy: VasculaturePatellar Plexus
Anastomoses of descending branch of lateral circumflex femoral a., anterior tibial recurrent a., and genicular branches
Popliteal Artery Med./Lat. Superior Genicular Middle Genicular – enters capsule
post. to supply ligaments and synovium
Med./Lat. Inferior Genicular Circumflex Fibular
Gross Anatomy: Nerve SupplySciatic nerve
Tibial n.Common
peroneal n. Wraps around
head of fibula
Saphenous branchesRun deep to
pes anserinus
Patellar DislocationPredisposition
Genu valgumOverweightPatellar hypermobilityWeak quadriceps
MechanismsDirect contact to
medial sideExternal tibial
rotation with forceful quadriceps contraction
Patellar DislocationVastus
medialis strainTearing of
medial patellar retinaculum
Hemarthrosis Reduces with
extension
Patellar Dislocation: DiagnosisObvious if not yet
reducedPatellar
hypermobility/ apprehension test
X-ray/MRI only necessary to rule out osteochondral fractures, other associated injuries
Patellar Dislocation: TreatmentKnee extensionAspiration to relieve
discomfort and check for fat in blood
Surgery unnecessary unless osteochondral fracture or complete rupture of MPFL
Crutches, PRICESRehabilitation focusing
on vastus medialis
Meniscal TearsShear force from femurAcute or degenerativeAthletes, elderly,
overweightVascular zone?Horizontal
Within substanceLongitudinal
Bucket handle – ACL riskRadial or vertical
Parrots beak
Medial Meniscus TearTears easier than
lateral due to certain traits
SquattingInternal rotation of
tibia with knee flexedMember of “unhappy
triad”Medial meniscusMCLACL
Medial Meniscus: DiagnosisExamination
McMurray’s testApley’s compression
testMRI
Low-signal intensity (black triangle ) = normal
White interruption = lesion
Arthroscopy as last resort
Medial Meniscus: TreatmentPRICES for isolated and minimal tearPartial arthroscopic meniscectomy most
common
Lateral Meniscus TearLower incidenceOften more painfulMore likely to incur
radial or parrots beak
Not rare for anterior horn
Discoid meniscusWrisberg varietyCongenital (1.5-
3%)MM only 0.1 –
0.3%
femur
Discoid meniscus
Lateral Meniscus: Diagnosis/TreatmentSame techniques as
for medial meniscusMcMurray’s test
and Apley’s test performed with internal tibial rotation
MRI slightly less accurate than with MM
Treatment similar
Medial Collateral Ligament Attached to fibrous
capsule and MMInjury rarely isolated –
“unhappy triad”Can tear with external
rotation (skiing), but more commonly from valgus or abduction force (football)
Pain localized to medial joint line, but can subside following Grade III tearLeads to further injury
MCL: Diagnosis: ExaminationAbduction stress test
First at 30Again at full extension
Rule out PCL tear
Anterior drawer test with external rotation of tibiaHip flexed 45Knee flexed 90Tibia rotated 30 ext.Anterior rotation of
medial tibial condyle
MCL: Diagnosis: ImagingX-ray
Only useful for young patients to differentiate from epiphyseal fracture
Taken at 20-30 flexion Enlarged joint space = tear
MRICoronal scanNormal MCL looks thin,
taut, low-signalGrade I: indistinct MCL
(edema)Grade II: thicker, looserGrade III: severe edema
MCL: TreatmentSurgery necessary for
compound injuryCrutches + PRICES +
rehab for Grade I, II only if isolated
Grade III tears may require surgical repair, but immobilization can be effective if isolated (rare)3-4 months recovery
SurgeryOpen incisionMidsubstance
ruptures suturedTear from bone
repaired with suture anchors
Lateral Collateral LigamentCourses slightly
posteriorSprained least frequently
Adduction force rareBF, popliteus, IT tract
Flexed knee = isolated tear
Anteromedial blow hyperextension/ postero-lateral corner injury
Risk to common peroneal nerveFoot drop, sensation loss
LCL: Diagnosis: ExaminationAdduction stress test
At 30, then full extensionExt. rotation recurvatum
Lift legs by great toesRecurvatum + ext rotation +
varus = PL corner injuryPosterolateral drawer test
Tibia externally rotated, posterior force applied
Reverse pivot shift testKnee 90, tibia ext. rotated With valgus, slowly extendedTemporary posterior
subluxation of lateral tibial condyle around 30
Forcibly reduces with extension
LCL: Imaging and TreatmentMRI
Coronal oblique scan
Sagittal scan to rule out fibular fracture, avulsion
Tear looks less taut or discontinuous – no thickening
TreatmentSimilar to MCLGrade III usually
requires surgery
Anterior Cruciate LigamentMost common knee injury
among athletesAM fibers taut in flexion
Check anterior displacementPL fibers taut in extension
Check rotationHyperextension, internal
rotation – rarely isolated injury from contact force
“unhappy triad”May tear from tibia (3-10%),
from femur (7-20%), or in midportion (70%)Proximal end receives
branch from middle genicular a. Internal rotation of right knee
(LEFT KNEE)
ACL: Diagnosis: ExaminationHistory, large hemarthrosisAutonomic symptomsAnterior drawer test
Tibia neutral, pull ant.NOT RELIABLE BY ITSELF
Lachman testKnee only flexed 15-20
Pivot shift/jerk testStart in extension, tibia
internally rotated, valgusSlowly flex, lateral tibial
condyle temporarily subluxates anteriorly ~30
Reduces with further ext.Jerk test opposite (90 o)
ACL: Diagnosis: ImagingX-ray
Segond fracture of lateral tibial condyle ACL tear with it
75-100%Tibial spine
avulsion in young patients
MRI – 95% accuracyAll 3 planes in full
extensionEdema/hemorrhage
often obscures ACLNormal ACL Torn ACL
ACL: TreatmentExtrasynovial, heals
poorlyPartial, isolated
tears may be treated with PRICES, rehab, bracing of slightly flexed knee
Most tears, athletes will require reconstruction
Posterior Cruciate LigamentBroader, longer, strongerPM and AL fiber bundlesReceives better vasc. from
MGA, synovial membraneChecks post. displacementTears much less frequently
Only in isolation when “dashboard knee” injury
Hyperextension in sports, especially with side force
Falling to ground with foot plantar flexed
Posterior view
Anterior view
Medial femoral condyle
PCL: DiagnosisPosterior drawer test
Neutral start vital!Gravity or sag test
Hips at 45 or 90, compare tibial tuberosities for sag
Abduction/adduction stress test at full extension
X-ray to confirm sag testMRI shows lower-signal
intensity for intact PCL compared to ACL due to its fiber organization Take on all 3 axes, but
best is sagittal oblique
negative positive
PCL: TreatmentControversial PRICES , rehab, bracing for most
isolated tearsRehab focused on quadriceps muscles for
compensatory anterior drawerSurgery avoided when possible because
PCL not easy to access without additional risk factors
Prognosis good because better blood supply = revascularization
Cruciate Ligament ReconstructionComplete excision
followed by graft insertion
AllograftAutograftPatellar, quadriceps,
hamstrings, calcaneus tendons used
Undergoes biological modifications: inflamed, necrotic revascularization extrinsic fibroblasts repopulate
ACL ReconstructionAutografts
B-PT-BQuadruple hamstrings
Semitendinosus, gracilisOnly replace AM
Double-BundleProvides rotational
stabilityBTB as AM bundle
Fixed at 20ST as PL bundle
Fixed at 90
PCL ReconstructionUsually allograft –
calcaneus tendonIncorporates well
with long-term stability
BTB and ST often too short
Can achieve full function with reconstruction of just AL bundle A. Low-power view cross section of PCL 11
years after calcaneus tendon graft. B. High-power
A B
Future of ReconstructionGoals:
Improve recovery timeImprove remodeling of insertion sitesImprove nervous and vascular restoration
With biological manufacture of:Growth factors, cytokinesAntibiotics
Techniques:Gene therapy – viral/non-viral vector delivers specific
geneTissue engineering – mesenchymal stem cells
