Concussion,ormildtraumaticbraininjury,incidencerateshavereachedepidemiclevelsandimpairedposturalcontrolisacardinalsymptom.Thepurposeofthisreviewistoprovideanoverviewofthelinearandnon-linearassessmentsofpost-concussionposturalcontrol.Thecurrentacuteevaluationforconcussionutilizesthesubjectivebalanceerrorscoringsystem(BESS)toassessposturalcontrol.Whilethesensitivityoftheoveralltestbatteryishigh,thesensitivityoftheBESSisunacceptablylowand,withrepeatadministration,isunabletoaccuratelyidentifyrecovery.Sophisticatedmeasuresofposturalcontrol,utilizingtraditionallinearassessments,haveidentifiedimpairmentsinposturalcontrolwellbeyondBESSrecovery.Bothassessmentsofquietstanceandgaithaveidentifiedlingeringimpairmentsforatleast1monthpost-concussion.Recently,theapplicationofnon-linearmetricstoconcussionrecoveryhavebeguntoreceivelimitedattentionwiththemostcommonlyutilizedmetricbeingapproximateentropy(ApEn).ApEn,mostcommonlyinthemedial-lateralplane,hassuccessfullyidentifiedimpairedposturalcontrolintheacutepost-concussiontimeframeevenwhenlinearassessmentsofinstrumentedmeasuresareequivalenttohealthypre-injuryvalues;unfortunatelythesestudieshavenotgonebeyondtheacutephaseofrecovery.Onestudyhasidentifiedlingeringdeficitsinposturalcontrol,utilizingShannonandRenyientropymetrics,whichpersistatleastthroughclinicalrecoveryandreturntoparticipation.Finally,limitedevidencefromtwostudiessuggestthatinpidualswithaprevioushistoryofasingleconcussion,evenmonthsoryearsprior,maydisplayalteredApEnmetrics.Overall,non-linearmetricsprovideafertileareaforfuturestudytofurthertheunderstandingofposturalcontrolimpairmentsacutelypost-concussionandaddressthecurrentchallengeofsensitiveidentificationofrecovery.
