AAOS 2026 BASIC

2026




0

,1- InKtheKcontextKofKjointKarthroplasty,KtheKalpha-
defensinKimmunoassayKtestKisKusefulKforKtheKdetectionKof?

1*asepticKloosening.K2*me

talKcorrosion.K3*periprost

heticKinfection.K4*boneKing

rowth.



CorrectKanswerK3

Alpha-
defensinKisKaKproteinKreleasedKbyKactivatedKneutrophilsKinKresponseKtoKinfection.KTheKdetectionKofKalpha-
defensinKinKsynovialKfluidKisKhighlyKsensitiveKandKspecificKasKaKmarkerKofKperiprostheticKinfection.KAsepticKl
ooseningKandKtheKboneKingrowthKofKprosthesesKgenerallyKareKdetectedKradiographically.KMetalKcorrosion
Kissues—inKmetal-on-metalKprostheses,KforKexample—


generallyKareKfollowedKusingKbloodKmetalKionKlevels.

2- InKposttraumaticKarthritis,KtheKinitialKinjuryKstimulatesKtheKproductionKofKinflammatoryKcytokines.KWhichK
K cytokineKisKproducedKatKtheKhighestKlevelKonKtheKfirstKdayKafterKinjury?K

1*Interleukin-6K(IL-

6)K2*Interleukin-1KbetaK(IL- ILK-
1BKTN
1β)K3*ChemokineKligandK22K(CCL F-a

-22)

4*Damage-associatedKmolecularKpatternsK(DAMPs)



CorrectKanswerK2

TheKdevelopmentKofKarthritisKafterKjointKinjuryKisKcommonKandKcanKresultKfromKmultipleKcauses,Kinclud
ingKcartilageKcontusion,KmeniscalKinjury,KligamentKtear,KorKintra-
articularKfracture.KTheKaccuracyKofKreductionKdoesKnotKnecessarilyKpreventKtheKdevelopmentKofKposttr
aumaticKarthritis.KDataKfromKanimalKstudiesKofKposttraumaticKarthritisKdemonstrateKtheKproductionKofKi
nflammatoryKcytokinesKthatKleadKtoKchondrocyteKdeathKandKmatrixKdestruction.KInKtheKfirstKfewKdaysKa
fterKinjuryKKIL-K
1βK(predominantly)KandKtumorKnecrosisKfactorKalphaKareKtheKprimaryKcytokinesKproduced,KfollowedKbyK
K


nitricKoxide,KmatrixKmetalloproteinases,KandKaggrecanases,KwhichKdegradeKtheKchondralKmatrixKCCL-
K


22KKincreasesKatKaroundK5KdaysKafterKinjury,Khowever.KOtherKfactorsKcalledKDAMPs,KwhichKareKgenerate
dKthroughKtheKmechanicalKorKenzymaticKdegradationKofKjointKtissues,KalsoKstimulateKanKinnateKinflamm
atoryKresponse.

,3- WhatKisKtheKmainKfunctionKofKlubricinKinKsynovialKjoints?




1*ServesKasKaKcomponentKofKtheKextracellularKmatrixK2

*InhibitsKmatrixKmetalloproteinase

3*IncreasesKcross-

linkingKbetweenKcollagenKfibersK4*ReducesKtheKcoeffic

ientKofKfrictionKinKtheKjoint



CorrectKanswerK4

LubricinKreducesKtheKfrictionKbetweenKtheKsurfacesKinKtheKjoint,KleadingKtoKdecreasedKshearKforcesKgoingK
throughKtheKhyalineKcartilage.KItKisKaKglycoproteinKthatKisKproducedKbyKtheKchondrocytesKinKtheKsuperficialK
zoneKandKisKnotKaKprimaryKcomponentKofKtheKextracellularKmatrix.KAKlackKofKlubricinKhasKbeenKassociatedKK
withKsyndromesKcausingKarthriticKchangesKatKanKearlyKageK

4- Anti-

sclerostinKantibodyKincreasesKboneKformationKbyKtargetingKwhatKmolecularKpathway?KK1*Wn

t

2*BoneKmorphogeneticKproteinK(BMP)K3*No

tch

4*IndianKhedgehog



CorrectKanswerK1



AllKofKtheKlistedKfactorsKserveKcriticalKfunctionsKinKboneKformation.KOnlyKBMP-
basedKtherapiesKcurrentlyKareKFDAKapproved,Khowever.KSclerostinKisKanKextracellularKantagonistKofKWntKs
ignalingKand,KtoKaKlesserKKextent,KBMPKsignaling.KBlosozumabKcurrentlyKisKanKinvestigationalKantibodyKthe
rapyKdesignedKtoKblockKsclerostin’sKabilityKtoKinhibitKWntKsignaling,KnettingKaKpositiveKeffectKonKboneKform
ation.KInKaKphaseK2KtrialKinvolvingK120KpostmenopausalKwomen,K1KyearKofKblosozumabKtreatmentKresulte
dKinKaK17%KincreaseKinKboneKmineralKdensityKinKtheKlumbarKspine.

, 5- FiguresK1KthroughK3KdisplayKradiographsKandKanKMRIKfromKaK29-year-
oldKmanKwhoKhasKcomplainedKofKleftKlegKpainKsinceKsustainingKaKgunshotKwoundK18KmonthsKago.KHeKdeni
esKanyKfeversKorKchillsKbutKdoesKhaveKpainKandKdrainageKfromKhisKwound.KHisKerythrocyteKsedimentationK
rateK(ESR)KisK105Kmm/hK(referenceKrange:K0-20Kmm/h),KC-
reactiveKproteinK(CRP)KlevelKisK12Kmg/LK(referenceKrange:K0.08-
3.1Kmg/L),KwhiteKbloodKcellK(WBC)KcountKisK8,000K/µLK(referenceKrange:K4500-
11000K/µL),KandKvitaminKDKlevelKisK15Kng/mLK(referenceKrange:K20-40ng/ml).

WhatKisKtheKtissueKindicatedKbyKtheKarrowKinKFigureK4?K

FigureK1