Rev. bras. ortop. vol.51 número2

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

Original

article

Q-angle

in

patellofemoral

pain:

relationship

with

dynamic

knee

valgus,

hip

abductor

torque,

pain

and

function

夽

Gabriel

Peixoto

Leão

Almeida

,

Ana

Paula

de

Moura

Campos

Carvalho

e

Silva

,

Fábio

Jorge

Renovato

Franc¸a

_,

_Maurício

_Oliveira

_Magalhães

_,

_Thomaz

_Nogueira

_Burke

_,

Amélia

Pasqual

Marques

a_{DepartmentofPhysiotherapy,SpeechTherapyandOccupationalTherapy,FaculdadedeMedicina,UniversidadedeSãoPaulo,SãoPaulo,}

SP,Brazil

b_{DepartmentofPhysiotherapy,FaculdadedeMedicina,UniversidadeFederaldoCeará,Fortaleza,CE,Brazil}

a

r

t

i

c

l

e

i

n

f

o

Articlehistory:

Received22March2015 Accepted28May2015

Availableonline9February2016

Keywords: Knee

Patellofemoralpainsyndrome Manualstrengthdynamometer

a

b

s

t

r

a

c

t

Objective:Toinvestigatetherelationshipbetweentheq-angleandanteriorkneepain sever-ity, functionalcapacity, dynamickneevalgus andhip abductortorque inwomen with patellofemoralpainsyndrome(PFPS).

Methods:Thisstudyincluded22womenwithPFPS.Theq-anglewasassessedusing goniom-etry:theparticipantswerepositionedindorsaldecubituswiththekneeandhipextended, andthehipandfootinneutralrotation.Anteriorkneepainseveritywasassessedusinga visualanalogscale,andfunctionalcapacitywasassessedusingtheanteriorkneepainscale. Dynamicvalguswasevaluatedusingthefrontalplaneprojectionangle(FPPA)oftheknee, whichwasrecordedusingadigitalcameraduringstepdown,andhipabductorpeaktorque wasrecordedusingahandhelddynamometer.

Results:Theq-angledidnotpresentanysignificantcorrelationwithseverityofkneepain (r=−0.29;p=0.19),functionalcapacity(r=−0.08;p=0.72),FPPA(r=−0.28;p=0.19)or isomet-ricpeaktorqueoftheabductormuscles(r=−0.21;p=0.35).

Conclusion: Theq-angledidnot presentanyrelationshipwithpain intensity,functional capacity,FPPA,orhipabductorpeaktorqueinthepatientswithPFPS.

©2016SociedadeBrasileiradeOrtopediaeTraumatologia.PublishedbyElsevierEditora Ltda.Allrightsreserved.

夽

WorkperformedintheLaboratóriodeInvestigac¸ãoFisioterapêuticaClínicaeEletromiografia,UniversidadedeSãoPaulo,SãoPaulo, SP,Brazil.

∗ _{Correspondingauthor.}

E-mail:gabrielalm@hotmail.com(G.P.L.Almeida). http://dx.doi.org/10.1016/j.rboe.2016.01.010

Ângulo-q

na

dor

patelofemoral:

relac¸ão

com

valgo

dinâmico

de

joelho,

torque

abdutor

do

quadril,

dor

e

func¸ão

Palavras-chave: Joelho

Síndromedadorpatelofemoral Dinamômetrodeforc¸amanual

r

e

s

u

m

o

Objetivo: Investigararelac¸ãoentreoângulo-qeintensidadeda doranteriornojoelho, capacidadefuncional,valgodinâmicodejoelhoetorqueabdutordoquadrilemmulheres comsíndromedadorpatelofemoral(SDPF).

Métodos: Participaram doestudo 22 mulheres comSDPF. Oângulo-qfoi avaliado pela goniometria,asparticipantesforamposicionadasemdecúbitodorsalcomjoelhoequadril estendidoequadrilepéemrotac¸ãoneutra.Aintensidadedadoranteriordojoelhofoi avaliadapelaescalavisualanalógicadedoreacapacidadefuncionalcomaescaladedor anteriornojoelho.Ovalgodinâmicofoiavaliadopeloângulodeprojec¸ãonoplanofrontal dojoelho(APPF),registradocomcâmeradigitaldurantestepdown,eopicodetorquedos abdutoresdoquadrilcomdinamômetromanual.

Resultados: Oângulo-qnãoapresentoucorrelac¸ãosignificativacomaintensidadedador nojoelho(r=−0,29;p=0,19),capacidadefuncional(r=−0,08;p=0,72),ângulodeprojec¸ão noplanofrontaldojoelho(r=−0,28;p=0,19)epicodetorqueisométricodosmúsculos abdutores(r=−0,21;p=0,35).

Conclusão: Oângulo-qnãoapresentourelac¸ãocomaintensidadedador,capacidade fun-cional,ângulodeprojec¸ãonoplanofrontaldojoelhoepicodetorquedosabdutoresdo quadrilempacientescomSDPF.

©2016SociedadeBrasileiradeOrtopediaeTraumatologia.PublicadoporElsevier EditoraLtda.Todososdireitosreservados.

Introduction

Theq-anglewasfirstdescribed byBrattstroem.1 _Thisangle isformedbythe intersectionoftwolinesthatcross atthe centerofthepatella:onegoingfromtheanterosuperioriliac spine(ASIS)tothecenterofthepatellaandtheotherfrom theanteriortuberosityofthetibiatothecenterofthepatella; andtheotherfromtheanteriortuberosityofthetibiatothe centerofthepatella.1_{Theq-angleiswidelyusedfor} evalu-atingpatientswithkneeproblems,especiallypatellofemoral painsyndrome(PFPS).Thelargertheq-angleis,thegreater the lateralizationforce onthe patella, which increasesthe retropatellarpressurebetweenthelateralfacetofthepatella andthelateralfemoralcondyle.2_{Thecontinuouscompressive} forcesbetweenthesestructuresmaygiverisetoPFPSand,over thelongterm,causedegenerationofthejointcartilageofthe patella.2,3_{HubertiandHayes}4_{reportedthata10%increasein} theq-angleincreasedthestressonthepatellofemoraljoint by45%.

However,therearedivergencesintheliteratureregarding therelationshipbetweentheq-angleandPFPSincase–control studies.5,6 _{Moreover,prospectivestudieshavenotsupported} thehypothesisthatgreaterq-anglesareariskfactorfor devel-opmentofPFPS.7–9

Notonlydoestheq-angleaffectthestaticalignmentofthe lowerlimbinthe frontalplane, butalsothe lever-arm dis-tancebetweenthecentersofthehipandknee jointsalters thecapacityofthehipabductormusclestogeneratetorque.10 However,itisquestionablewhetherthestaticvalgus(q-angle) affects the dynamic valgus of the knee and the peak iso-metrictorqueofthehipabductormuscles.Furthermore,few

studieshavecorrelatedtheq-anglewithkneepainintensity andfunctionalcapacityamongwomenwithPFPS.11,12

Thus,theobjectiveofthisstudywastoascertainthe rela-tionshipoftheq-anglewithkneepainintensity, functional capacity,projectionangleinthefrontalplaneandpeak iso-metric torqueofthe hip abductormuscles, amongwomen withpatellofemoralpain.Ourhypothesiswasthattheq-angle wouldhavepositivecorrelationswiththedynamicvalgusof thekneeandwiththeintensityofanteriorkneepain;andthat itwouldpresentnegativecorrelationswiththepeakisometric torqueofhipabductionandwithfunctionalcapacity,among womenwithPFPS.

Materials

and

methods

Participants

A cross-sectional study was conductedon 22 womenwith PFPS,ofages19–45years.Womenwereselectedforthisstudy becauseofthehighincidenceofPFPSinthispopulation,in comparisonwithmen,andbecauseofthestructural, strength-relatedandkinematicdifferencesinthehipsbetweenthetwo sexes.Theagegroupwaschosensoastoexcludepossible degenerative alterationstothekneeand hip.13 _The partici-pantswererecruitedbymeansofpersonalcommunication, throughorthopedicclinicsandthroughleafletsdisseminated withinouruniversity.

Thepatientsincluded inthe patellofemoralgroup (PFG) presented patellofemoral pain that was reproduced in at leasttwoofthefollowingactivities:goingupordownstairs, squatting,kneeling, remainingseated foralong time, per-formingisometrichipcontraction,jumpingandrunning.They reported feeling pain upon palpation ofthe lateral and/or medialfacetofthepatella;insidiouspainthathadlastedfor atleastthreemonths;painscoringatleastthreeonavisual analogscale(VAS)forpain;14_{painuponcompressionofthe} patellawiththekneeflexedat15◦_{orwithpalpationofthe}

lat-eralretinaculumagainsttheposteriorsurfaceofthepatella;15 andatleast86pointsonthepainscaleforanteriorkneepain (maximum=100points).16

Thefollowingwomen were excluded from bothgroups: those with previous surgery on their knees, hips, ankles and/orspine;historiesofpatellardislocation;clinicalevidence ofknee instability;meniscallesions orotherintra-articular lesions; evidence of edema; Osgood-Schlatter or Sinding-Larsen-Johanssen; patellar tendinopathy; chondral lesions; osteoarthritis;bodymassindex(BMI)greaterthan28kg/m2_; structural abnormalities in the spine; discrepancy of leg length of 2cm, evaluated by means of real and apparent measurement; neurologicalinvolvementthat compromised the abilityto walk; lumbarpain formore than two weeks over the last six months; or muscle or joint injuries in thehip.

Procedures

Alltheevaluationsweremadebythesameinvestigator,who hadfiveyearsofclinicalexperience.Onlythesymptomatic limb(orthemostsymptomaticlimb)wasevaluatedineach patient.

Q-angle

Theq-anglewasevaluatedbymeansofauniversal goniome-ter, with the participant in dorsal decubitus and with the hipandknee completelyextended,hip intheneutral rota-tionpositionandfeetintheneutralposition.Theanglewas calculatedbymeansoftheintersectionformedbytwolines crossing at the center of the patella. The first line went from the ASISto the centerof thepatella and the second fromtheanteriortuberosityofthetibiatothecenterofthe patella.17_{Theintraandinter-evaluatorreliabilityofq-angle} measurementsusingagoniometerhasbeenwellestablished intheliterature18_{andthecorrectionthroughMRIevaluation} ismoderate.18

Functionalcapacityandpain

TheintensityofthepainwasevaluatedbymeansofaVAS. Thisscalerangedfrom0(absenceofpain)to10(maximum pain) and is reliable and valid for pain complaints in the knee.19 _{Functional capacity was evaluated using the} ante-riorkneepainscale(AKPS),whichisaquestionnairewith13 itemsandscoringbetween0(worstpossible) and100(best possible).20

Dynamickneevalgus

Kneekinematicsduringstep-downwasevaluatedbymeans offilmingin2Dusingadigitalcamera(SonyCyber-shot DSC-W35;7.2megapixels).Thefrontalplaneprojectionangle(FPPA) oftheknee wasdefined.Threeself-adhesivemarkerswere placed:atthemidpointbetweenthemedialandlateral malle-oli;atthemidpointbetweenthemedialandlateralfemoral condyles;andataposition30cmabovethekneemarker, fol-lowingastraightlinefromthismarkertotheanterosuperior iliacspine(ASIS).15

The heightofthe stepwas standardizedby takinginto account10% oftheheightofeach individual.Each partici-pant’sfootwaspositionedonastandardlineandthepoint atwhichthe heeltouchedthegroundwas standardizedat a distance of 5cm from the step. The digital camera was atadistanceof2mfromthe step,atthelevel ofthe knee that wastobeevaluated.Before thesubjectsdidthe tests, they were given verbal guidance about how to do them properly, witha demonstration of the depth and speed of the test, but without specifying the orientation ofthe hip andknee.

Alltheparticipantsperformedthreetests,with60sof res-ting between them,as the effective start ofthe test. Each step-downwasdonefor5s,referringtotheeccentricand con-centricphases,and weremarkedusingachronometer.The foot participants (1s) were instructed toperformthe step-downslowlyuntiltheheelofthesuspendedfoottouchedthe ground(3s).Thiswasfollowedbyaslowreturntothe ini-tialposition(5s).Afteraperiodofadaptationtothetest,the meanfromfivetestswasusedfortheanalysisoneachlower limb.15

AsequenceofimageswascapturedusingtheVirtualDub software(copyright1998–2009AveryLee).TheFPPAwas cal-culated through the postural assessmentsoftware (PAS) v. 0.68,basedondigitizingspatiallydefinedpointsthatenabled measurementofbodyangles.ThevaluesoftheFPPAwere con-sideredtobenegativewhenthekneemarkerwasmedialto thethighandankle(dynamicvalgus),andwereconsideredto bepositivewhenthekneemarkerwaslateraltotheothertwo (dynamicvarus).15

Abductortorqueofthehip

Musclestrengthwasevaluatedusingamanualdynamometer (NicholasManualMuscleTester,LafayetteInstrument Com-pany, Lafayette,Indiana, USA). Studies have demonstrated thatthisequipmenthasexcellentreliabilityinintraand inter-observerevaluation.21,22

theeventofanycompensationthatmighthavecompromised thetest result,or anyoccurrence ofdiscrepant values,the testwasdisregardedandwasrepeatedafter20s.Toanalyze thedata,theforce (N)wasconvertedintotorque(Nm)and wasnormalizedwithbodyweight(kg),throughthefollowing formula:(Torque[Nm]/Weight[kg])×100.

Thetorqueofthehipabductorswasevaluatedwiththe patientinlateraldecubitusonanexaminationbed.Thelimb tobeevaluatedwaspositionedathipabductionof20◦_,

exten-sionof10◦_{andneutralrotation,withthekneeextended.The}

non-evaluatedlimbwas positionedathipand kneeflexion of45◦_{.Thecenterofthedynamometerwaspositioned5cm}

proximallytothecenterofthelateralmalleolus.Theleverarm wasmeasuredasthedistancefromthecenterofthegreater trochantertothecenterofapplicationofthedynamometeron thelowerlimb.

Statisticalanalysis

TheShapiro–Wilktestwasusedtoascertainwhetherthedata showednormaldistribution.Descriptiveanalyses(meanand standarddeviation)wereperformedonallthevariables.

Pearson’scorrelationcoefficientwasusedtoanalyzethe associationsbetweentheq-angle(independentvariable)and thepainintensity,functionalcapacity,dynamickneevalgus and hip abductor torque(dependentvariables).The values ofrwereinterpretedasfollows:0–0.19=none;0.2–0.39=low; 0.4–0.69=moderate;0.7–0.89=high;and0.9–1=veryhigh.For allthe statisticalanalyses,the SPSS17.0 softwarefor Win-dowswas used (Statistical Package forthe Social Sciences Inc.,Chicago,IL,USA),andthesignificancelevelwastakento be5%.

Table1–Clinicalandanthropometriccharacteristicsof thepatientswithpatellofemoralpainsyndrome (mean±SD).

Mean SD

Age(years) 28.1 9.3

Weight(kg) 59.9 7

Height(m) 1.63 0.07

BMI(kg/m2_{) 22.4 2.6}

Durationofpain(months) 22.1 16.5 Q-angle(degrees) 17.8 2.7

VAS(0–10) 5.8 1.8

AKPS(0–100) 71 10.1

FPPA(degrees) −11.9 5.9 Hipabduction(Nm/kg) 75.5 24.6

BMI,bodymassindex;VAS,visualanalogscaleforpain;AKPS, ante-riorkneepainscale;FPPA,frontalplaneprojectionangle.

Results

Thedemographicandclinicalcharacteristicsofthepatients withPFPSareshowninTable1.

The q-angle did not present any significant correlation with pain intensity (r=−0.29; p=0.19), functional capacity (r=−0.08;p=0.72),dynamickneevalgus(r=−0.28;p=0.19)or hipabductortorque(r=−0.21;p=0.35)(Fig.1).

Discussion

Theobjectiveofthisstudywastoascertaintherelationship betweentheq-angleandthevariablesofpainintensity, func-tionalcapacity,FPPAofthekneeandpeakisometrictorqueof

10

8

6

4

2

0

100

80

60

40

20

0

15

10

5

0 30

40

20

10

0

0 10 20

q-angle (degrees)

30 0 10 20

q-angle (degrees)

30

0 10 20

q-angle (degrees)

30 0 10 20

q-angle (degrees)

30

FPPA (degrees)

VAS (0-10)

AKPS (0-100)

Hip abduction (Nm/kg)

A

B

C

D

thehipabductormuscles.However,thepresentstudydidnot findanyrelationshipbetweentheq-angleandthedependent variablesanalyzed.

Ithasbeentheorizedthatanexcessiveq-angleisrelated todevelopmentofPFPS,throughincreasedcompressiveforces betweenthelateralfacetofthepatellaandthelateralfemoral condyle.2,4 _{Nevertheless,this hypothesishasnotbeen} con-firmedthroughprospectivestudies.Thijsetal.8_andRamskov et al.9 _{prospectively monitored novice street runners and} foundthattheq-angledidnotdifferbetweentheathleteswho developedPFPSand thosewho didnot.Thus, theydidnot considerittobeariskfactor.Similarfindingswerereported byBoling et al.7 _{from a prospectivestudy on 1319} partici-pants,withthreeyearsoffollow-up. Furthermore,arecent systematicreviewwithmeta-analysis23_{confirmedthelackof} relationshipbetweenanexcessiveq-angleanddevelopment ofPFPS.

Excessivedynamickneevalgusisanabnormalityof neu-romuscularcontroloverthelowerlimb.Thiscreatesalateral force vector on the patella and increases the compressive loadsbetweenthelateralfaceofthepatellaandthelateral femoralcondyle.24_{Studiershavedemonstratedthatpatients} withPFPSpresentgreaterdynamickneevalgusthando con-trols without PFPS.15,25 _{Theoretically, an excessive q-angle} mayfavorexcessivedynamickneevalgusbecauseofthemore medialorientation of the knee in the frontal plane. How-ever,ourresultsshowthatpatientswithanexcessiveq-angle donothavegreaterdynamickneevalgus.Corroboratingour findings,ithasbeensuggestedthatthemagnitudeofthe q-anglehasminimaleffectonalterationsofthekinematicsof thelowerlimbanddoesnotincreasethekneejointanglein thesagittalandtransverseplanesduringrunning.26_Pantano etal.27_{reportedthatindividualsclassifiedashavingalarger} q-angle(≥17◦_{)didnotpresentagreaterkneevalgusangle,in}

comparisonwiththosewithsmallerq-angles(≤8◦_).

Interest-ingly,thenegativecorrelationbetweenthe q-angleandthe kneeabductionmoment indicatesthatgreaterq-anglesare associatedwithsmallerdynamicvalgus.10

Weaknessofthe hip abductor muscles hasconsistently beenfoundinpatientswithPFPS,withdeficitsrangingfrom 21to29%,incomparisonwithcontrolswithoutPFPS.28 _The capacityofthehipmusclestocontrolexcessivedynamicknee valgusdependsontheircapacitytogeneratetorque.Factors thatmodifytheleverarmofthelower limbsmayalterthe capacityofthehipmusclestogeneratetorque.Studieshave shownthatanatomicalalterationsofthehip inthe frontal plane,suchasfemoraloffset,arecorrelatedwiththestrength of the hip abductor muscles.29 _{However, we did not find} anystudiesinvestigatingtherelationshipbetween anatom-icalalterationsinthefrontalplaneoftheknee(q-angle)and thestrengthofthehipmuscles.Ourresultsdonotsupport thehypothesisthattheq-anglehasarelationshipwiththe capacityofthehipmusclestogeneratetorque.

Increased patellofemoral stress may result in increased intensity of anterior pain in the knee, with consequent diminutionoffunctionalcapacityandanearlydegenerative processinthepatellofemoraljoint.2_{However,wedidnotfind} any relationship between the q-angle and the intensity of anterior knee pain and functional capacity among women withPFPS.SimilarresultswerefoundbyPivaetal.,11_whodid

notfindanyevidenceforarelationshipbetweentheq-angle andpainandfunctionalcapacity.LivingstonandMandigo12 did not fundant correlation between the q-angle and the intensityofkneepainamongpatientswithPFPS.

Theabsenceofprospectivestudiessupportingthe hypoth-esis that the q-angle is a risk factor for PFPS6–8 _{and the} lackofrelationshipbetweentheq-angleandpainintensity, functionalcapacity11_{andvariablethatarepotentially} modifi-ablethroughphysiotherapy(dynamicvalgusandhipmuscle strength)diminishtheclinicalrelevanceofevaluatingthe q-angleasthefocusofpreventionandtreatmentofPFPS.

It is important to highlight that the present study has some limitations. The cross-sectional nature of this study didnotallowcause-and-effectrelationshipstobeestablished betweenthevariablesanalyzedandPFPS.Patellofemoralpain is of multifactorial origin, and other possible anatomical, biomechanical,neuromuscularandpsychologicalfactorsthat werenotstudiedmayvaryaccordingtotheq-angle.

Conclusion

Theq-angledidnotpresentanyrelationshipwithpain inten-sity,functionalcapacity,frontalplaneprojectionangleofthe kneeorpeakisometrictorqueofthehipmuscles.Itcanbe sug-gestedthatevaluatingtheq-anglemaynotbringadditional informationfortreatingpatientswithPFPS.Thus, physiother-apeuticassessmentandtreatmentshouldbedirectedtoward otherpotentiallymodifiablevariables.

Conflicts

of

interest

Theauthorsdeclarenoconflictsofinterest.

Acknowledgements

Research Support Foundation of the State of São Paulo (Fundac¸ão de Amparo à Pesquisa doEstado de São Paulo, FAPESP),no.2012/10768-0.

r

e

f

e

r

e

n

c

e

s

1.BrattstroemH.Shapeoftheintercondylargroovenormally andinrecurrentdislocationofpatella.Aclinicaland X-ray-anatomicalinvestigation.ActaOrthopScandSuppl. 1964;68:1–148.

2.HeinoBrechterJ,PowersCM.Patellofemoralstressduring walkinginpersonswithandwithoutpatellofemoralpain. MedSciSportsExerc.2002;34(10):1582–93.

3.LeeTQ,MorrisG,CsintalanRP.Theinfluenceoftibialand femoralrotationonpatellofemoralcontactareaandpressure. JOrthopSportsPhysTher.2003;33(11):686–93.

4.HubertiHH,HayesWC.Patellofemoralcontactpressures.The influenceofq-angleandtendofemoralcontact.JBoneJoint SurgAm.1984;66(5):715–24.

6. LankhorstNE,Bierma-ZeinstraSM,vanMiddelkoopM. Factorsassociatedwithpatellofemoralpainsyndrome:a systematicreview.BrJSportsMed.2013;47(4):193–206. 7. BolingMC,PaduaDA,MarshallSW,GuskiewiczK,PyneS,

BeutlerA.Aprospectiveinvestigationofbiomechanicalrisk factorsforpatellofemoralpainsyndrome:theJoint UndertakingtoMonitorandPreventACLInjury(JUMP-ACL) cohort.AmJSportsMed.2009;37(11):2108–16.

8. ThijsY,PattynE,VanTiggelenD,RombautL,WitvrouwE.Is hipmuscleweaknessapredisposingfactorforpatellofemoral paininfemalenovicerunners?Aprospectivestudy.AmJ SportsMed.2011;39(9):1877–82.

9. RamskovD,JensenML,OblingK,NielsenRO,ParnerET, RasmussenS.Noassociationbetweenq-angleandfoot posturewithrunning-relatedinjuries:a10weekprospective follow-upstudy.IntJSportsPhysTher.2013;8(4):

407–15.

10.ParkSK,StefanyshynDJ.GreaterQanglemaynotbearisk factorofpatellofemoralpainsyndrome.ClinBiomech(Bristol, Avon).2011;26(4):392–6.

11.PivaSR,FitzgeraldGK,IrrgangJJ,FritzJM,WisniewskiS, McGintyGT,etal.Associatesofphysicalfunctionandpainin patientswithpatellofemoralpainsyndrome.ArchPhysMed Rehabil.2009;90(2):285–95.

12.LivingstonLA,MandigoJL.BilateralQangleasymmetryand anteriorkneepainsyndrome.ClinBiomech(Bristol,Avon). 1999;14(1):7–13.

13.RussellKA,PalmieriRM,ZinderSM,IngersollCD.Sex differencesinvalguskneeangleduringasingle-legdrop jump.JAthlTrain.2006;41(2):166–71.

14.BolglaLA,MaloneTR,UmbergerBR,UhlTL.Hipstrengthand hipandkneekinematicsduringstairdescentinfemaleswith andwithoutpatellofemoralpainsyndrome.JOrthopSports PhysTher.2008;38(1):12–8.

15.WillsonJD,DavisIS.Utilityofthefrontalplaneprojection angleinfemaleswithpatellofemoralpain.JOrthopSports PhysTher.2008;38(10):606–15.

16.WatsonCJ,ProppsM,RatnerJ,ZeiglerDL,HortonP,SmithSS. Reliabilityandresponsivenessofthelowerextremity functionalscaleandtheanteriorkneepainscaleinpatients withanteriorkneepain.JOrthopSportsPhysTher.

2005;35(3):136–46.

17.SmithTO,HuntNJ,DonellST.Thereliabilityandvalidityof theQ-angle:asystematicreview.KneeSurgSportsTraumatol Arthrosc.2008;16(12):1068–79.

18.DraperCE,ChewKT,WangR,JenningsF,GoldGE,Fredericson M.Comparisonofquadricepsanglemeasurementsusing short-armandlong-armgoniometers:correlationwithMRI. PMR.2011;3(2):111–6.

19.CrossleyKM,BennellKL,CowanSM,GreenS.Analysisof outcomemeasuresforpersonswithpatellofemoralpain: whicharereliableandvalid?ArchPhysMedRehabil. 2004;85(5):815–22.

20.daCunhaRA,CostaLO,HespanholJuniorLC,PiresRS,Kujala UM,LopesAD.Translation,cross-culturaladaptationand clinimetrictestingofinstrumentsusedtoassesspatients withpatellofemoralpainsyndromeintheBrazilian population.JOrthopSportsPhysTher.2013;43(5):332–9. 21.PivaSR,GoodniteEA,ChildsJD.Strengtharoundthehipand

flexibilityofsofttissuesinindividualswithandwithout patellofemoralpainsyndrome.JOrthopSportsPhysTher. 2005;35(12):793–801.

22.RobinsonRL,NeeRJ.Analysisofhipstrengthinfemales seekingphysicaltherapytreatmentforunilateral patellofemoralpainsyndrome.JOrthopSportsPhysTher. 2007;37(5):232–8.

23.LankhorstNE,Bierma-ZeinstraSM,vanMiddelkoopM.Risk factorsforpatellofemoralpainsyndrome:asystematic review.JOrthopSportsPhysTher.2012;42(2):81–94. 24.PowersCM.Theinfluenceofabnormalhipmechanicson

kneeinjury:abiomechanicalperspective.JOrthopSports PhysTher.2010;40(2):42–51.

25.LevingerP,GilleardW,ColemanC.Femoralmedialdeviation angleduringaone-legsquattestinindividualswith patellofemoralpainsyndrome.PhysTherSport. 2007;(8):163–8.

26.HeiderscheitBC,HamillJ,CaldwellGE.InfluenceofQ-angle onlower-extremityrunningkinematics.JOrthopSportsPhys Ther.2000;30(5):271–8.

27.PantanoKJ,WhiteSC,GilchristLA,LeddyJ.Differencesin peakkneevalgusanglesbetweenindividualswithhighand lowQ-anglesduringasinglelimbsquat.ClinBiomech (Bristol,Avon).2005;20(9):966–72.

28.PrinsMR,vanderWurffP.Femaleswithpatellofemoralpain syndromehaveweakhipmuscles:asystematicreview.AustJ Physiother.2009;55(1):9–15.