hamstrings strength in knee osteoarthritis before and after total knee arthroplasty: a cross-sectional study 夽

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SOCIEDADE BRASILEIRA DE ORTOPEDIA E TRAUMATOLOGIA

w w w . r b o . o r g . b r

Original Article

Comparative analysis of quadriceps and

hamstrings strength in knee osteoarthritis before and after total knee arthroplasty: a cross-sectional study ^夽

Naasson Trindade Cavanellas, Victor Rodrigues Amaral Cossich,

Eduardo Becker Nicoliche

^∗

, Marilena Bezerra Martins, Eduardo Branco de Sousa, José Inácio Salles

InstitutoNacionaldeTraumatologiaeOrtopedia,LaboratóriodePesquisaNeuromuscular,RiodeJaneiro,RJ,Brazil

a r t i c l e i n f o

Articlehistory:

Received18November2016 Accepted9January2017 Availableonline23February2018

Keywords:

Musclestrength

Arthroplasty,replacement,knee Osteoarthritis

a bs t r a c t

Objective:Comparethemaximalisokinetic musclestrengthofkneeextensorandﬂexor musclesbetweenpatientswithkneeosteoarthritisandpatientssubmittedtototalknee arthroplasty.

Methods:Volunteersweredividedintoﬁvegroups(n=20):Control;AhlbäckIandII;Ahlbäck IV;sixmonthsaftertotalkneearthroplasty;12monthsaftertotalkneearthroplasty.An isokinetickneestrengthevaluationwasconductedforthequadricepsandhamstringsat 60^◦/s.

Results:Signiﬁcantdifferencesinthepeaktorqueofthequadricepsandhamstringswere foundamongthegroups(p<0.001).TheAhlbäckIV,six-month,and12-monthpostoperative groupsdemonstratedlowervalueswhencomparedtotheControlandAhlbäckIandII groups.WhenpercentagevalueswerecomparedtotheControlgroup,meandifferences rangedfrom7%to41%.

Conclusion:Patientswithhealthykneesorearlystageosteoarthritishavehigherquadriceps andhamstringsstrengthsthanthosewithamoreadvancedstageofthedisease,evenafter kneereplacement.Theseﬁndingssuggestthatthetraditionalrehabilitationprogramsdo notrecoverstrengthtolevelsobservedinindividualswithoutkneeosteoarthritis.

creativecommons.org/licenses/by-nc-nd/4.0/).

夽StudyconductedatInstitutoNacionaldeTraumatologiaeOrtopedia,RiodeJaneiro,RJ,Brazil.

∗ Correspondingauthor.

E-mail:eduardo.nicoliche@gmail.com(E.B.Nicoliche).

https://doi.org/10.1016/j.rboe.2018.02.009

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Análisecomparativadaforc¸adoquadrícepsedosisquiotibiaisna osteoartritedojoelhoanteseapósaartroplastiatotaldojoelho:um estudotransversal

Palavras-chave:

Forc¸amuscular Artroplastiadojoelho Osteoartrite

r e s u mo

Objetivo:Compararaforc¸amuscularisocinéticamáximadosmúsculosextensoreseﬂexores dojoelhoentrepacientescomosteoartritedojoelhoepacientessubmetidosàartroplastia totaldojoelho.

Métodos: Osvoluntáriosforamdivididosemcincogrupos(n=20):Controle,AhlbäckIeII; AhlbäckIV;seismesesapósartroplastiatotaldojoelho;12mesesapósartroplastiatotaldo joelho.Otestedeforçavoluntáriaisocinéticamáximafoifeitoparamensuraçãodaforça doquadrícepseisquiotibiaisa60/s.

Resultados: Foramachadasdiferençassignificativasentreopicodetorquedoquadríceps edosisquiotibiais(p<0,001).OsgruposAhlbäckIV,seismesese12mesesapóscirurgia mostraramvaloresmaisbaixosquandocomparadoscomosgruposcontroleeAhlbäckIe II.QuandoosvalorespercentuaisforamcomparadoscomogrupoControle,asdiferenças médiasvariaramde7%a41%.

Conclusão: Ospacientescomjoelhossaudáveisouosteoartriteemestágioinicialapresen- tarammaiorforçanoquadrícepse nosisquiotibiais doquepacientesemestágiomais avançadodadoença,mesmoapósaATJ.Essesachadossugeremqueosprogramastradi- cionaisdereabilitaçãonãorecuperamaforçanosníveisobservadosemindivíduossem osteoartritedojoelho.

creativecommons.org/licenses/by-nc-nd/4.0/).

Introduction

Knee osteoarthritis (OA) is the most common orthopedic disorderamongthepathologiesofthisjoint.¹OAclinicalman- agement isage-related; this condition hasa majorimpact onfunctionandindependence,includinglimitationsinloco- motionanddomestictasks.^2–4Recentresearchassociatesthe functionaldeclineinOAwithmuscleweakness,particularly inthequadricepsandhamstrings.^5,6

In addition to physicalexercise, pharmacological treat- mentandlifestyle changesaresuggestedasaconservative treatmentforOA.⁷Asthediseaseprogresses,withthereduced effectofthetherapeuticinterventionsandthehighimpair- mentofthepatient’sfunctionalityatotalkneearthroplasty (TKA) is often considered as the best treatment option.⁸ DespitethefactthatTKAdecreasespainlevelsinpatientswith OA,thequadricepsand hamstringmusclestrength deﬁcits persistaftersurgery.^9–11

Althoughthecausesofquadricepsandhamstringweak- ness are unknown, the main causes appear to be disuse atrophyandactivationdeficits.¹²Thusithasbeenobserved thatthemainfocusofattentionregardingmusclestrength deficitinOAandTKAisdirectedtoquadricepsstrength.^13,14 Inturn,theinterpretationoftheimportanceofhamstringsin OAandTKAhasnotincreased,despitethefactthat,together withthequadriceps, the hamstringsprovidethe structural andfunctionalstabilityofthisjoint.¹⁴Understandingthemag- nitudeofmusclestrengthinOAandTKAcanhelpidentify disease-modifying triggers and refine rehabilitation proce- durestoimprovepatients’qualityoflife.Therefore,thisstudy

isaimedatcomparingthemaximalisokineticmusclestrength ofthekneeextensorandﬂexormusclesbetweenpatientswith kneeOAandthoseundergoingTKA,andtoanalyzetheper- centagealteration rateand the ratioofmaximal isokinetic musclestrengthbetweenthekneeextensorsandﬂexors.The authors’hypothesiswasthatthe12-monthpost-TKAgroup wouldpresenthighervaluesofmusclestrengththantheother groups.

Material and methods

Thesampleconsistedofpatientsattendedtoattheoutpatient clinic of the Specialized Knee Surgery Care Center (Cen- trodeAtenc¸ãoEspecializadaemCirurgiadoJoelho[CAECJ]) of the National Institute ofTraumatology and Orthopedics Jamil Haddad(Instituto Nacional de Traumatologia eOrto- pediaJamilHaddad[Into]).Tables1–5describetheinclusion and exclusioncriteriausedforpatientselection,aswellas thecompositionofthefollowingexperimentalgroups(n=20 in each): (1) asymptomatic individuals (control); (2) radiological diagnosis ofOA – Ahlbäck gradesI and II (OA-1/2);

Table1–Inclusionandexclusioncriteria–Control group.

Inclusion Exclusion

Withamedicalrecordofmuscularinjuriesin thelowerlimbsandarticularinjuriesinthe knees.

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Table2–Inclusionandexclusioncriteria–OA-1/2group.

Inclusion Exclusion

AhlbäckgradeIouII Withamedicalrecordoftrauma Infectionorprevioussurgeryinthe studiedjoint

Kneevarusorvalgus>10^◦

Previoussurgeryintheaffectedknee

Table3–Inclusionandexclusioncriteria–OA-4group.

Inclusion Exclusion

AhlbäckgradeIV Withamedicalrecordoftrauma Infectionorprevioussurgeryinthe studiedjoint

Kneevarusorvalgus>10^◦

Previoussurgeryintheaffectedknee

Table4–Inclusionandexclusioncriteria–TKA-6group.

Inclusion Exclusion

Kneerangeofmotion>100^◦ Infectionorprevioussurgeryin thestudiedjoint

6monthspost-operative Musclecontracturewithknee ﬂexion>15^◦

Rheumaticinfections Severeosteoporosis Kneevarusorvalgus>10^◦

Table5–Inclusionandexclusioncriteria–TKA-12 group.

Inclusion Exclusion

Kneerangeofmotion>100^◦ Infectionorprevioussurgeryin thestudiedjoint

12monthspost-operative Musclecontracturewithknee ﬂexion>15^◦

Rheumaticinfections Severeosteoporosis

(3) radiological diagnosis of OA – Ahlbäck gradeIV (OA-4);

(4) sixmonths afterTKA (TKA-6);and (5) 12 months after TKA(TKA-12).AllparticipantsreadandsignedanInformed ConsentForminwhichtheaimsoftheexperimentandthe evaluationconditionsweredescribedindetail.Allprocedures werepreviouslyapprovedbyInto’sEthicsCommittee,inaccor- dance with the Resolution of the National Health Council No. 466, of 12/12/2012.^◦ Project registration number: CAAE 34971714.0.0000.5273.

Ahlbäckradiologicalclassiﬁcation

Anteroposterior (AP) and lateral (P) view knee radiographs wereobtainedwithmonopedal support¹⁵;the raywascen- teredontheinferiorpoleofthepatella,with1mtube-to-film distance.Forthelateralview,thepatientwasplacedinlat- eraldecubitus ontheside ofthe affectedknee, whichwas flexedat20^◦.Thecentralray wasdirectedverticallytothe medialsideofthekneejoint,withcephalicangulationof5^◦ andtube-to-filmdistanceof1m.Allradiographsweretaken inthesameradiologydepartmentduringroutineoutpatient care;nootherimageswererequiredjustforthepurposeofthe

study.TheclassiﬁcationproposedbyAhlbäck,¹⁶modiﬁedby Keyesetal.,¹⁷wasusedtoclassifythedegreeofOA.

Maximumisokineticvoluntarystrength

Formusclestrengthassessments,anisokineticdynamome- ter (CSMI^®, Humac Norm^®, MA, United States) was used.

All subjects were seated,with the lateral femoral condyle alignedwiththedynamometer’srotationalaxisandtheankle attachedtotherodofthekneeevaluationassessmenttoolby avelcrostrip.Aconcentric-concentrictestwasperformedfor kneeextensionandflexion,withafixedvelocity(60^◦/s)and fiverepetitions.¹⁸Initially,thevolunteersunderwentawarm- uproutineandfamiliarizedthemselveswiththeequipment andtheisokineticcontraction,throughrepetitionsatthesame velocityusedforthetest.Thehighestinstantaneoustorque foundforquadriceps(QUA)andhamstring(HAM)groupswas consideredthepeaktorque.Evaluationswereperformedonly ontheaffectedlimbofeachpatient;forthecontrolgroup,the dominantlimbwasassessed.

Statisticalanalysis

Theanalyseswereinitiatedbynormalizingthepeaktorque values by each participant’s body weight. Subsequently,to analyzetheproportionalityofmusclestrength,theHAM/QUA ratiovalueswerecalculatedfromthepeaktorquevaluesof theQUAandHAMmuscles.Thus,thedependentvariablesof thestudywere:(1)peakQUAtorque,(2)peakHAMtorque,and (3)HAM/QUAratio.Demonstrativestatistics(mean±standard deviation)wereusedfordatapresentation.One-wayANOVA was calculated separately for group comparisons. Subse- quently,Tukey’sposthoctestwasusedtoassessthedifferences betweenpairs.Forallanalyses,thesigniﬁcancelevelwassetat p≤0.05.Inordertoqualitativelyanalyzetherateofalteration, degradation, preservation, orgrowth ofthe QUA and HAM muscularstrength,calculationsweremadetoconvertthese values intopercentage differenceindices (%).It isunder- stoodthat%,asthecalculatedindex,hasasreferencethe meanvaluesoftheextensorandﬂexormusclesofthecon- trol group 1.11and 0.76Nmkg⁻¹, respectively (describedin theresultssection)andcalculatedaccordingtotheformula presentedbelow.

%=

(individualstrengthvalue×100) referencevalue

−100

Results

Tocheckthechangesinmusclestrengthofthekneeextensor andﬂexormusclesinOApatientswhounderwentTKA,100 volunteersagedbetween46and87years(50womenand50 men)wereselectedanddividedintoﬁveexperimentalgroups.

AllpatientsintheOAgroupunderwentthesameanalgesic procedure;andthepatientswhounderwentTKAfollowedthe institutional protocol ofphysiotherapeutic rehabilitationto improverangeofmotionandstrength.Duringtheexecution ofstrengthevaluations,nopatientcomplainedofexcessive painand/orpresentedlimitationsduringtheisokinetictest.

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Table6–Demographicdataofthepatients(mean±SD).

Control OA-1/2 OA-4 TKA-6 TKA-12

Men 7 10 10 13 10

Women 13 10 10 7 10

Age(years) 67.9±7.2 56.3±5.4 66.1±9.3 69.1±7.0 65.8±6.1

Height(cm) 156.8±11.8 167.2±9.2 165.7±5.8 161.0±6.9 164.7±7.4

Bodyweight(kg) 70.5±24.0 81.6±12.6 78.2±12.5 83.1±15.7 78.9±11.8

BMI(kg/m²) 28.3±5.9 29.1±2.9 25.2±4.9 32.0±5.2 26.2±5.6

Table7–Maximumisokineticforceat60^◦/sofknee extensorsandﬂexors(peaktorque/bodyweight– Nmkg⁻¹andpercentagedifferenceofthecontrol– mean±SD).

Groups Quadriceps Hamstrings

Peaktorque(Nmkg⁻¹) % Peaktorque(Nmkg⁻¹) %

Control 1.11±0.47 0 0.76±0.29 0

OA-1/2 0.99±0.49 −11.0 0.71±0.33 −7.0 OA-4 0.56±0.22â −50.0 0.42±0.16^b −45.0 TKA-6 0.54±0.24â −51.0 0.51±0.19^c −33.0 TKA-12 0.65±0.29â −41.0 0.55±0.20 −28.0

a SigniﬁcantlydifferentfromQUAcontrolandQUAOA1/2(p<0.01).

b SigniﬁcantlydifferentfromHAMOA-1/2andcontrol(p<0.001;

both).

c SigniﬁcantlydifferentfromHAMcontrol(p=0.016).

2.5

2.0

1.5

1.0

0.5

0.0

Control

Peak torque (Nm.Kg-1)

AO 1/2 AO 4 TKA 6 TKA 12

a a

a

Fig.1–Quadricepspeaktorque–60^◦/sintheknee (mean±SD).

aSigniﬁcantlydifferentfromcontrolandOA-1/2(p<0.001).

Blackcircle=control;whitecircle=AO1/2;black triangle=AO4;whitetriangle=TKA6;andblack square=TKA12.

Table6presentsthedemographicdataofthepatientsallotted totheirrespectivegroups.

ThepeakQUAandHAMtorquevaluesarelistedinTable7 andrepresentedgraphicallyinFigs.1–3

.Thevarianceanalysisshowedasigniﬁcantdifferencefor theextensionstrength(F=11.15;p<0.001),aswellasforﬂex- ion(F=6.75;p<0.001).

In the OA-4, TKA-6, and TKA-12 groups, the peak QUA torquevaluesweresigniﬁcantlylowerthaninthecontroland OA-1/2groups (p<0.001). Thevaluesobservedinthe OA-4,

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0.0

Control

Peak torque (Nm.Kg-1)

AO 1/2 b

AO 4 TKA 6 TKA 12

a

Fig.2–Hamstringpeaktorque–60^◦/sintheknee (mean±SD).

aSigniﬁcantlydifferentfromcontrol(p=0.016).^b

SigniﬁcantlydifferentfromcontrolandAO-1/2(p<0.0001;

both).Blackcircle=control;whitecircle=AO1/2;black triangle=AO4;whitetriangle=TKA6;andblack square=TKA12.

0

–10

–20

–30

–40

–50

–60

Control AO 1/2 AO 4

Δ% (%)

TKA 6 TKA 12

Fig.3–PercentagevariationofQUAandHAMmuscular forceinthedifferentstagesofOAevolutionandafterTKA (mean).

TKA-6,andTKA-12groupswerenotdifferentfromeachother;

thesamewasfoundforthecontrolandOA-1/2groups.Inthe OA-4,TKA-6,andTKA-12groups,themeanpeakHAMtorque valueswerelowerthaninthecontrolandOA-1/2groups.

Thecontrolgrouppresentedasigniﬁcantlyhighertorque peak when compared with the OA-4 (p<0.001) and TKA-6

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Table8–HAM/QUAratioat60^◦/sintheknee (mean±SD).

Control 0.71±0.16

OA-1/2 0.70±0.20^a

OA-4 0.78±0.18

TKA-6 0.94±0.32^a

TKA-12 0.92±0.38

a Signiﬁcantlydifferentfromcontrol(p<0.001).

groups(p=0.016).TheOA-1/2groupalsopresentedasignif- icantlyhigher valuethan that observed inthe OA-4group (p<0.001).ThevaluesobservedintheTKA-12groupwerebor- derlinesigniﬁcantwhencomparedwiththoseinthecontrol group(p=0.069).Thesamewasobservedwhencomparingthe OA-1/2andTKA-6groups(p=0.082).

Table 8 presents the HAM/QUA ratio values. ANOVA demonstratedasigniﬁcantdifference(F=3.806andp<0.01).

Post hocanalysis demonstrated that the OA-1/2 and TKA-6 groupsweresigniﬁcantlydifferentfromthecontrolgroup.The valuesobservedintheTKA-12groupwereborderlinesigniﬁ- cantwhencomparedwiththoseintheOA-1/2group(p=0.07) andinthecontrolgroup(p=0.09).

Discussion

Understandingchanges inquadricepsand hamstringmus- clestrengthinpatientswithOAandafterTKAisimportant toimprovetreatment proceduresinjoint diseaseand after arthroplasty. Experiments measuring the strength of knee extensorshave identified losses ofaround50% in thepre- operativephaseand onemonthafter TKA,¹⁹ which makes QUAmuscleweaknessacharacteristicinpatientswithknee OA.⁵ Thesystematic review and meta-analysis by Øiestad etal.⁶demonstratedthatweaknessofkneeextensorsisasso- ciatedwiththeriskofdevelopingOA.Inthissense,thisstudy observedkneeextensorstrengthdeficitinpatientswithOA AhlbäckgradeIV.Inturn,thelowdiseaseseveritypresented bypatientswithAhlbäckgradesI-IIkneeOAwasnotenough topresentasignificantimpactonQUAstrength.

Despite some recommendations for HAM strength improvement in OA,^5,12,20 few studies compared flexor strengthindifferentstagesofOAandTKA.Slemendaetal.²¹ failedtoobservesignificantalterationsinkneeflexorstrength inpatientswithKellgrenandLawrencegrades2orhigher.In anotherstudy,alsowithpatientswithKellgrenandLawrence grades 2 or higher, it was observed that the isometric torqueofpatientswithOA waspoorwhen comparedwith healthy controls(Cheingand Hui-Chan).²² Thediscrepancy between the studies bySlemenda et al.²¹ and Cheing and Hui-Chan²² should be attributed to the fact that between KellgrenandLawrencegrades2and4,theimpactofdisease severityonmusclestrengthmaybedifferent.Inthepresent study,flexorstrength deficit wasobserved onlyinAhlbäck gradeIV.

When comparing results of patients with OA Ahlbäck gradesI andIIand gradeIV,apossibleinabilitytoachieve normalpatternsofmuscularstrengthofpatientsinthelast stageofthediseasewasobservedinbothextensorandﬂexor

muscles of the knee. In OA Ahlbäck grades I-II, the decreaseandobliterationofthejointspaceobservedonthe radiographs^15,23werenotsufﬁcienttogeneratesigniﬁcantdif- ferencesintheQUAandHAMstrengthwhencomparedwith acontrolgroupwithouttheseradiologicalchanges.

TheauthorsbelievethatthelowperformanceinQUAand HAMstrengthinthegroupofpatientswithOAAhlbäckgrade IVisclinicallyimportant,sincetheintegrationofthesemuscle groupsisassociatedwithkneestability.²Inthisrelationship betweenagonistsandantagonists,ononehandtherearethe QUAmuscles,whicharetheprimaryextensormechanismof thekneewhenwalking,running,orotheractivitiesofdaily living²⁴and ontheother handthereare theHAMmuscles, which,besidesbeingtheprimarymechanismofkneeﬂexion, theyalsoprotectthekneefromeccentriccontractionduring the supportphase,bothtocushionthe jointand togener- ate limbdecelerationduringgait.²⁵ TheQUA isthe largest setofmusclesthatactonthekneejoint,withgreatpoten- tial to produceand absorbthe forces acting onthat joint.

Severalclinicalstudieshavedemonstratedthedevelopment of QUA strength after an exercise program, showing pain reductionandimprovementsinfunctionalabilitiesincases ofOA.^26,27Inturn,intheagonistandantagonistrelationship, theHAMmuscleshavemultiplerolesincontrollingkneeﬂex- ionand hip extension,maintainingthe stabilityofthis set ofjointsduringdisplacementtasks.¹²Interventionsthrough exerciseintheHAMmuscleshaveprovidedincreasedrange ofmotion,greatermusclepowerandstability,withimproved painsymptomsandfunctionalityinpatientswithAO.⁵There- fore,adequatefunctioningofkneeextensorsandﬂexors,not onlyisolatedbutinaunitedandintegratedmanner,isessen- tialtoprovidedynamicstabilityforthisjoint.²²

The relationbetween HAM and QUA strength has been reportedindifferentstudies.^28,29TheratioofHAM/QUAisoki- netic for healthy subjects has been established to range between 0.6and 0.7 at an angular velocity of 60^◦/s.^18,28,29 The mathematical ratio between the peak HAM and QUA torque observed in this study demonstrated that the control group followed the trend of the indexes expressed in theliterature.^28,29RecentstudiesofthisratioinOApatients show different values, due to QUA weakening.^13,20 In the presentstudy,borderlinevaluesfortheHAM/QUAratiowere observed in the OA-1-2 and OA-4 groups. The groups of patientswhounderwentTKA(TKA-6andTKA-12)alsoshowed values outside the normal range, with results close to 1, which demonstrate a high degradation of QUA strength.

Thepresentresultsdemonstratethatthereisagreaterdis- crepancy in the HAM/QUA ratio in relation to the control group.

Ameanreductiondifferenceof11%inextensionforcewas observedbetweenthecontrolgroupandOAAhlbäckgradeI andIIpatients;intheAhlbäckgradeIVgroup,whencompared tothecontrolgroup,itwaspossibletoobserveanexacerbated dropof50%inQUAstrength.TheHAMstrengthfollowedthe sametrend,withdeclinesof7%forAhlbäckgradesIandII,and 45%forgradeIV.Nosigniﬁcantdifferencesintheproportion ofstrengthdeclinebetweenkneeextensorsandﬂexorswas observedinthisstudy.Bothmusclegroupsweakenedinthe sameproportioninpatientswithOAAhlbäckgradesIandII andAhlbäckgradeIV.

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Despite the emphasis on rehabilitation procedures on muscle strength, OA patients with Ahlbäck grade IV may present inhibition of muscle activation, especially of the quadriceps.^30,31QUAweakeningandcentralactivationfailure are common in knee joint injuries.³¹ The persistent phe- nomenonofweakeningandfailureintheactivationofknee extensors can be attributed to arthrogenic muscle inhibition,acontinuousreﬂexinhibitionofthemusclemassacting onan injured joint.Thisresponseis inherenttothe joint;

itisintendedtoprotectitfrom furtherdamage,discourag- ingtheuse oftheinjuredjoint,possiblytopreventpainful movements.^30,31 Thisprotectivemechanismhasahighcost, resultinginmuscleweaknessthatoftencannotbecorrected intherehabilitationprocess.Consideringthatthemuscular strengthperformanceofpatientsclassifiedasAhlbäckgrade IandIIdidnotpresentsignificantdifferencesinrelationto thecontrolgroup,unlikethegroupofpatientsclassified as AhlbäckgradeIV,itcanbeinferredthatthedegreeofinjuryis relatedtothemagnitudeofthearthrogenicmuscleinhibition.

Thefactthatourstudydemonstratedthatthehamstringsalso showareductioninstrengthinpatientswithGradeIVOA (Ahlbäck),inthesameproportionasthequadriceps,suggests thattheﬂexorsofthisjointalsoundergoaarthrogeniceffect causedbyOA.

WhenconservativetreatmentfailstoalleviateOAsymp- toms,TKA becomes the therapeuticinterventionof choice toimprovedebilitatingpainandfunctionalcapacity.³²Inthe presentstudy,it wasobservedthatinpatients whounder- wentTKA,kneeextensorandflexorstrengthpresentedthe samepatternidentifiedinpatientswithAhlbäckgradeIV.The resultsofthestudy byYoshidaetal.³³ indicatedaninverse relationship,inwhichthestrongestpatientssubmittedtoTKA tendedtoshowlower QUArecruitment,withthreemonths postoperatively.Thealteredneuromuscularpatterns ofthe QUAandHAMduringgaitcaninfluencethestrengthofthe formerafterTKA.³⁴PatientswhoundergounilateralTKAtend tounloadtheoperatedlimband shiftthemechanicalload tothecontralaterallimbjoints,evenoneyearaftersurgery.³⁵ ThelikelyasymmetryinQUAandHAMstrengthcausedbythe weakeningofthesemusclestructures,whichinthepresent studywasidentifiedforbothOAandTKAgroups,mayplaya roleinasymmetricloadinginTKApatients,asaddressedby Alnahdietal.³⁵

Conclusion

Arthrogenicmuscleinhibitionpreventstherehabilitationof both QUA and HAM strength in this degenerative process betweenAhlbäckgradeIVofOAand12 monthsafterTKA.

Ifactivationand atrophydeficitsare notspecificallyidenti- fiedand correctedduring rehabilitationinterventions, they will tend to persist. In agreement with the literature that addressesthestrengthdeficitinOAandTKA,thepresentfind- ingsindicatethattraditionalrehabilitationprogramsmaynot beenoughtoreverseQUAandHAMstrengthdeficiencies.

Conﬂicts of interest

Theauthorsdeclarenoconﬂictsofinterest.

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