Knee Joint Anatomy 101 - Clinical Bike Fit · Knee Joint Anatomy 101 Bone Basics There are three...
12
Knee Joint Anatomy 101 Bone Basics There are three bones at the knee joint – femur, tibia and patella – commonly referred to as the thighbone, shinbone and kneecap. The fibula is not typically associated with the knee because it lies outside the capsule and as associated with ankle function. We need to consider the osteological features (study of bones) of this joint to fully appreciate the numerous complex movements necessary to accomplish flexion and extension. The femoral head sits inside the acetabulum at the ball and socket hip joint with the neck connecting laterally to the greater trochanter. Distal features include the convex medial/lateral condyles, Intercondylar notch or patellar groove and adductor tubercle.
Transcript of Knee Joint Anatomy 101 - Clinical Bike Fit · Knee Joint Anatomy 101 Bone Basics There are three...
KneeJointAnatomy101
BoneBasics
Therearethreebonesatthekneejoint–femur,tibiaandpatella–commonlyreferredtoasthe
thighbone,shinboneandkneecap.Thefibulaisnottypicallyassociatedwiththekneebecauseitliesoutsidethecapsuleandasassociatedwithanklefunction.
Weneedtoconsidertheosteologicalfeatures(studyofbones)ofthisjointtofullyappreciatethenumerouscomplexmovementsnecessarytoaccomplishflexionandextension.
Thefemoralheadsitsinsidetheacetabulumattheballandsockethipjointwiththeneckconnectinglaterallytothegreatertrochanter.
Distalfeaturesincludetheconvexmedial/lateralcondyles,Intercondylarnotchorpatellargrooveand
adductortubercle.
Thefemurarticulatesatthetibialplateau.Thesecondylesareconcavemedially,convexlaterally,and
dividedbythetibialtubercles,whichfitsnuglyintotheIntercondylarnotchinextension.
Theanatomicalaxisofthefemurboneisdivergentfromthemechanicalaxis,descendingmediallyfromthecenterofthegreatertrochantertotheIntercondylarnotch;conversely,theanatomicaland
mechanicaltibialaxisarenearlyidentical.
Closeexaminationofthetibialandfemoralmedialcondylesofbothfemurandtibiaextendfurtherthantheirrespectivecounterparts,whichcreatesaphysiologicvalgusangleofthekneeapproximating180-
185-degrees.
Diagnosticcriteriaforabnormalfrontalplaneadductionis>185-degrees(GenuValgum)or</=175-degreesabduction(GenuVarum),measuredatthemedial-tibiofemoraljointinextension.
Theanteriororientationofbothlateralcondylesanda25-30-degreecurveonthemedialfemoralcondyleareprobablythemostdistinctfeaturesofthetibiofemoralarticulatingsurfacestructure.
Themedialfemoralcondylearticulatingsurfaceareaislargerandcurvedrelativetothelateralcondyle,
whichisflatter,smallerandmorecircular.Bothstructuresareconvex.
Atthetibialplateau,themedialcondyleisconcaveand50%largerthanthepartiallyconvexlateralcondyle.Thedegreeofposteriorslopevariesbetweencondyles,asdoestheamountofcartilage.
Thepatellaisembeddedwithintheretinaculalayerbetweenthefemurandtibia,attachedsuperiorlytothequadricepstendonandinferiorlytothepatellartendon.Exposedposteriorlytoarticulatewiththe
femoralsulcus,thesurfacecontainsacentralverticalridgeandfacets.
CartilageBasics
Hyalinecartilagecoversalargeportionofthefemoralcondylesandposteriorpatellatoreducepatellofemoralarticularfriction.
Fibrocartilagenousmenisciatthetibialplateaucreateasemi-flexiblehousingthatcompensatetibiofemoralobliquity.
Menisciattachedtothesurfaceofthetibialplateauimprovecongruence,pressuredistributionandarticulationatthetibiofemoraljoint.
Fixedtothetibiaatthehornsandcoronaryligamentstheyarejoinedanteriorlybythetransverse
ligament.
Thelateralmeniscusformsanearlycompletecircleandcoversamajorityofthetibialcondyle’ssurface,withanteriorandposteriorhorns(typically)blendingintotheattachmentoftheACL.Thereisno
attachmentbetweenthelateralmeniscusandthelateralcollateralligament,providingincreasedmobilityincomparisontothemedialmeniscus.
Thec-shapedmedialmeniscusislarger,butcoverssignificantlylesssurfaceareathenthelateral
meniscus.AnteriorfibersoftheACLblendwiththetransverseligamentandanteriorhornofthemedialmeniscus.Andcapsularattachmentsjointothedeepmedialcollateralligamentdirectlyandpatellavia
thepatellomeniscalligaments.
LigamentBasics
Ligamentscreatepassiveresistancetofacilitateoptimalkneefunctionandstability.
TibiofemoralLigaments:
ThedeepanteriorandposteriorcruciateareconsideredIntracapsularandextrasynovialbecausetheyexistinsidethejointcapsulebutoutsidethesynovialmembrane,crossinganterior/posterior&
posterior/anteriorbetweenfemurandtibia.
Themedial(tibial)collateralligamentcontainssuperficial(extracapsular)anddeep(capsular)components,betweenfemurandtibia,andthelateral(fibular)ligamentispurelyextracapsular,
connectingfemurtofibula.
PatellofemoralLigaments
Patellarmovementisinitiatedbythequadricepsandguidedbythemedial/lateraltibialandfemoralligaments.
KneeJointCapsule
Consistentwithothersynovialjoints,thekneeexistswithinacapsulemadeofconnectivetissueandbone.
Theouterlayerconsistsofafibrousmembranewithopeningsatthepatellaforthesuprapatellarbursaandlateraltibialcondyleforpoplitealmuscle,inseparablewithnumeroussupportingcapsularligaments.
Theinner-membranesecretessynovialfluid(andnutrients)toreducefrictionbetweenjointsurfaces
Bursaandfat-padsareinterspersedbetweenmuscles,tendonsandbonesasbuffersforfrictionandpressure.
.
MuscleBasics
Anteriormusclesofkneejointaremonoarticulating(articulate/crossone-joint)orbiarticulating(articulate/crosstwo-joints).
Musclesindirectlyinfluencingthekneeareindicatedwithbluearrows.
Posteriormusclesofthekneejointarealsomono-andbiarticulating.
Musclesindirectlyimpactingthekneeareindicatedwithbluearrows.
