Chapter6-MusculoskeletalSystemOVERVIEWHilkkaRiihimäkiMusculoskeletaldisordersareamongthemostimportantoccupationalhealthproblemsinbothdevelopedanddevelopingcountries.Thesedisordersaffectthequalityoflifeofmostpeopleduringtheirlifetime.Theannualcostofmusculoskeletaldisordersisgreat.IntheNordiccountries,forexample,itisestimatedtovaryfrom2.7to5.2%ofthegrossnationalproduct(Hansen1993;HansenandJensen1993).Theproportionofallmusculo-skeletaldiseasesthatareattributabletoworkisthoughttobeapproximately30%.Thus,muchistobegainedbypreventionofwork-relatedmusculoskeletaldisorders.Toaccomplishthisgoal,agoodunderstandingisneededofthehealthymusculoskeletalsystem,musculoskeletaldiseasesandtheriskfactorsformusculoskeletaldisorders.Mostmusculoskeletaldiseasescauselocalacheorpainandrestrictionofmotionthatmayhindernormalperformanceatworkorinothereverydaytasks.Nearlyallmusculoskeletaldiseasesarework-relatedinthesensethatphysicalactivitycanaggravateorprovokesymptomsevenifthediseaseswerenotdirectlycausedbywork.Inmostcases,itisnotpossibletopointtoonecausalfactorformusculoskeletaldiseases.Conditionscausedsolelybyaccidentalinjuriesareanexception;inmostcasesseveralfactorsplayarole.Formanyofthemusculoskeletaldiseases,mechanicalloadatworkandleisureisanimportantcausalfactor.Suddenoverload,orrepetitiveorsustainedloadingcaninjurevarioustissuesofthemusculoskeletalsystem.Ontheotherhand,toolowalevelofactivitycanleadtodeteriorationoftheconditionofmuscles,tendons,ligaments,cartilageandevenbones.Keepingthesetissuesingoodconditionrequiresappropriateuseofthemusculoskeletalsystem.Themusculoskeletalsystemessentiallyconsistsofsimilartissuesindifferentpartsofthebody,whichprovideapanoramaofdiseases.Themusclesarethemostcommonsiteofpain.Inthelowerbacktheintervertebraldiscsarecommonproblemtissues.Intheneckandtheupperlimbs,tendonandnervedisordersarecommon,whileinthelowerlimbs,osteoarthritisisthemostimportantpathologicalcondition.Inordertounderstandthesebodilydifferences,itisnecessarytocomprehendbasicanatomicalandphysiologicalfeaturesofthemusculoskeletalsystemandtolearnthemolecularbiologyofvarioustissues,thesourceofnutritionandthefactorsaffectingnormalfunction.Thebiomechanicalpropertiesofvarioustissuesarealsofundamental.Itisnecessarytounderstandboththephysiologyofnormalfunctionofthetissues,andpathophysi-ology-thatis,whatgoeswrong.Theseaspectsaredescribedinthefirstarticlesforintervertebraldiscs,bonesandjoints,tendons,musclesandnerves.Inthearticleswhichfollow,musculoskeletaldisordersaredescribedforthedifferentanatomicalregions.Symptomsandsignsofthemostimportantdiseasesareoutlinedandtheoccurrenceofthedisordersinpopulationsisdescribed.Currentunderstanding,basedonepidemiologicalresearch,ofbothwork-andperson-relatedriskfactorsispresented.Formanydisorderstherearequiteconvincingdataonwork-relatedriskfactors,but,forthetimebeing,onlylimiteddataareavailableonexposureeffectrelationshipsbetweentheriskfactorsandthedisorders.Suchdataareneededinordertosetguidelinestodesignsaferwork.Despitethelackofquantitativeknowledge,directionsforpreventioncanbeproposed.Theprimaryapproachtopreventionofwork-relatedmusculoskeletaldisordersisredesignofworkinordertooptimizetheworkloadandmakeitcompatiblewiththephysicalandmentalperformancecapacityoftheworkers.Itisalsoimportanttoencourageworkerstokeepfitthroughregularphysicalexercise.Notallmusculoskeletaldise...
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