Performance Tests for subjects with Patellofemoral Pain Syndrome

J unn ( l , l A t h l c r i cT r a i nin g 2 0 0 2 .3 1 ( 3 ) :2 5 6 _ 2 6 1 O by t h e N a r i o n aA l r h l e r iCT r a in e r Asso s' cia r io nln...
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J unn ( l , l A t h l c r i cT r a i nin g 2 0 0 2 .3 1 ( 3 ) :2 5 6 _ 2 6 1 O by t h e N a r i o n aA l r h l e r iCT r a in e r Asso s' cia r io nln. c u u u . j o u r n a lfoi r r hI e ti c t r ai nin g .o r g

IntraraterReliabilityof Functional PerformanceTestsfor subjects with Patellofemoral PainSyndrome Janice K. Loudon*;Doug wiesnerf; HeatherL. Goist-Foley*;cari Asjesf; KarenL. Loudon* *University of Kansas, Overland Park, KS; fSports Rehabilitationand physical Therapy, overland park, KS Janice K' Loudon,PhD, ATc, PT, contributedto conceptionand design; acquisitionand analysisand interpretationof thedata, and draftingand criticalrevisionand final approvat article.ooulg iviesner,ATC, Heather Goist-Fotey,MSpT, cari Asjes, .of .tite PT, and KarenLoudon,ATC, M)MT, PT, contribuledto conceptionind design; acquisition and anatysisandinterpretation of the data; and draftingand finat approva!of the afticte. Address correspondenceto Janice K. Loudon, PhD, ATC, PT, t)niversityof KansasMedical center, g,4g outtook, overlano Park, KS 66207.Address e-mail to [email protected] Objective: Patellofemoralpain syndrome (pFpS) is a com_ mon clinicalentity seen by the sports medicine specialist.The ultimategoal of rehabilitationis to returnthe patientto the hioh_ est functionallevel in the most efficientmanner. Therefore,ii is necessaryto assess the progress of patientswith pFpS using reliablefunctionalperformancetests. Our purposewas to eval_ uate the intraraterreliabilityof S functionalperformancetests in patientswith PFPS. Design and Setting: We used a test-retest reliabilitydesign in a c linicse tting . Subjects: Two groups of sublects were studied: those with PFPS (n : 29) and those with no known knee condition(n = 11). Th e PFPS g rou p inc luded 19 wom en and . 10m en w i t h a mean a ge o f 2 7.6 + 5 . 3 y ear s , height of 169. g0 * 10 . 5 c m , and weig ht of 6 9.5 9 + 15. 8 k g. The nor m al gr oup inc l u d e d7 women and 4 men with a mean age of 30.3 + 5.2 years, height of 169.5 5 * 9 .9 cm, a nd weight 69. 42 * 14. 6 k g. Measuremenfs: The reliabilityof 5 functional performance tests (anteromediallunge, step-down,single-legpress, bilateral squat, balance and reach) was assessed in 15 subiects with

PFPS. Secondly, the relationshipof the 5 functionaltests to parnwas assessed in 29 PFpS subjectsusing pearson product moment correlations.The limb symmetry index (LSl) was cal_ culated in the 29 PFPS subjects and compared with the group of 11 normal subjects. Resu/fs.' The 5 functional tests proved to have fair to high intrarater reliability.Intrarater reliabilitycoefficients(lCC 3,1) ranged from .79 to .94. For the pFpS subiects, a statistical differenceexisted between limbs for the anieromediallunge, step-down,single-legpress, and balance and reach. All func_ tional tests correlatedsignificanflywith pain except for the bi_ lateral squat; values ranged from .39 to .73. The average LSI for the PFPS group was B5%, while the average LSI for the normal subjectswas g7?o. Conclusions: The 5 functional tests proved to have good intraraterreliabilityand were relatedto changes in pain. Future researchis needed to examine interraterreliability,validity,and sensitivityof these clinicaltests. Key Words: step-down,squat, limb symmetry, Knee

atcllot'cmoralpain syndrome (PFpS) is a cornrnon clinical entity uscd to describea varicty ofpathologic conditions associatedwith the articulation betwcen the unclersurfaceof thc patclla and thc femoral condylcs. patcllofcmoral pain syndrontccan be causedby a variciy of factors, including quadriccpswcakncss,increasede anglc, faulty lower cxtren-ritymechanics,ovcrusc, and lateral retinaculum tisht_ ness.l.2Thc rnajor complaints of patients with pFpS ur..-diffusc kncc pain, patellar crepitus and locking, knec joint stiffncss, and dccrcasedactivity levels.s-7Onsct of symptoms is usually insidious and may occur bilaterally. Activities such as prolongcd sitting, stair desccnt,and squattingoften exaccrbate t he pa in.E The ultimate goal of rehabilitation for patients with pFpS rs return to thc highest functional level in the most cfficient rnanner.'/Accompanying this goal is the need for a testing rnethodthat is objective,rcliablc, and sensitivcto the changin! statusof PFPS. Comrnon objective measuresof knee function

include pain asscssmcnt,goniomctry, girth rlcasurcnlent,man_ ual musclc testing, and isokinetic evaluation. Howcver, thesc tcsts have bcen shown to be poor prcdictors 6f funs1j6n.6.l{) Functional testing is an attempt to evaluatc thc knec joint under conditions that mimic realistic functional dernands.per_ fomrance on functional tests depcnds on many variablcs,in_ cluding pain, swelling, crcpitus, ncurornuscularcoordination, muscular strength, and joint stability.ll The tests should bc time efflcient and simple to pcrforrn with minirnal instruction; they should requirc minirnal staff training and be conductecl within a clinical setting. Scveral functional knce tests arc described in the literature and include thc shuttle run, stair-runnlng test, verticaljump test, and hop 19515.10-12 Thesetcstsare useful after ligamentous knee injuries or othcr sport-related injuries, such as muscle strains or meniscus injuries, and arc not specific to the patellofemoraljoint. Functional performance tests that arc specific for pFpS s h o u l d b e c h o s e n b a s e d o n c l i n i c a l c v i d e n c l a n d t h e c ase o f

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replication among clinics and facilities. Pain is a factor associated with PFPS and is commonly used as a measurementto determine functional improvement. Chesworth et all3 evaluatcd the visual analog scale (a measure of pain) in patients with PFPS, finding poor day-to-day rcliability but good sensitivity to clinical changes.In addition to measuring pain dircctly, performance of a functional test may add infom.ration rcgarding muscle strength,endurance,proprioception,and balFunctional tests specific to PFPS should include wcightbearing stresswith various knee-flexion angles becausethese are common aggravatingpositions and require dynamic nruscular control. Post and Fulkerson8found that 86''/"of patients with patcllofernoralpain havc pain during stair climbing and 85% havc pain with squatting.The increascin pain with thcsc joint activitics is correlatedwith an increasein patcllofen.roral rcaction forcc,3.'1'8'i4 At prcscnt, no functional tcsts specificto thc patcllofcnroraljoint havc bccn reported in thc litcraturc. Wc cvaluatedthc following functional pcrfonrance tcsts in this study: anteromcdiallunge, step-down,single-legpress,bilatcral squat, ancl balance and reach. Thc antcrornediallunge is a multiplanar rnovement designed to challenge the latcral patcllofemoralarticulationwith thc valgus stressplaccd on the kncc cluring thc ntancuvcrl5 Thcorctically, as an individual lunges and thc ccntcr of gravity rnovcs fbrward and acrossthc body, thc pull of the quadriccps rnuscle causescomprcssive loading of thc lateral patellofcrnoralarticulation, a cotlrrron site of patcllofemoral syrnptonrs.The step-down nrirnics the function of stair dcsccnt, a cornnton aggravating factor. Thc loacl of thc patcllof'crnoraljoint with stair dcsccnt has bccn lcportcd to bc 3.5 tirncs body weight.rb A singlc-lcg prcss tcst was chosen to strcss thc patellof'entoral joint in a partial wcight-bcaring nrocic.This tcst can bc aclministcrcdearly in rchabilitation whcn a full squat nray bc too aggravating.To fufthcr challcngc thc patcllofcrroral .joint, a sccond tcst is a full wcight-bcaringbilatcral squat. Thc joint rcaction forcc of a squat to 90' is approxirnatcly 7.5 tinrcs body wcight.3 Thc balancc-ancl-rcach tcst, dcscribcd by Gray,ls spccifically challcn gcs sin glc-lcg b alanc c . Thc primary purposc of our study was to detcminc thc intraratcr rcliability of 5 functional pcrlbrrtrancctests on paticnts with PFPS. Sccondarypurposcswcrc to detcrntinelimb syrnlnctry indcx (t-SI) dif-fercnccsfor involvcd and uninvolved linrbs and to asscssthe rclationshirlbctwecn thc 5 functional tcsts and pain ratings. METHODS

Subjects Two groupsof subjccts wcrc includcdin this study,onc group with PFPS (n : 29) and a secondgroup with no known kncc condition (n : ll). The PFPS group included l9 wonren and l0 men with a mcan age of 2'7.6 'r 5.3 years, height of 169 .U0 | 1 0.5 cm, and weight of 69. 59 | 15. 8 k g. D a t a f r o m I 5 of these 29 subjects were used for the reliability tcsting. Inclusion critcria for the subjects in the PFPS group wcrc 2 of the following on initial assessment:pain on direct compression of the patella against the femoral condylcs with the knee in full cxtension,tendernesson palpation of the lateral surfacc of the patella,pain on resistedknec cxtension,or pain with isometric quadricepscontractionagainstsuprapatellarresistancewith the knee in slight flexion. These subjects'symp-

Figure'1. Anteromediallungetest.

toms wcrc consistentwith the cxccssive latcral prcssurcsyndrome as describedby Wilk et al.l7 Exclusion critcria for both groups included a history of patcllar trauma; subluxation;dislocation; confirmcd ligamcntous,meniscal,or fat-paddarnagc, evidcnce of tcndinitis, bursitis, or effusion; cvidcnce of rcferred pain from thc back or hip; osteochondralor chondral fiacturcs; or uppcr or lower motor neuron lssl6n.l8.leThc duration of patellofenroral pain averaged 5.2 rnonths for thc PFPS group. Thc normal group included 7 womcn and 4 nrcn w i t h a m c a n a g c o f 3 0 . 3 + 5 . 2 y c a r s , h c i g h t o f 1 6 9 .5 5 t 9 .9 cm, and wcight of 69.42 -r 14.6 kg. Thc norrnal subjcctswcrc used to compare the LSIs.

Experimental measurements Anteromedial lunge, left and right, For thc antcromcdral lungc, thc subject is lincd up bchind a starl linc. Thc tcst is pcrfbrrncd by having thc subject lungc forward with thc uninvolvcd limb so that thc front lcg is bcnt to 90' and crosscs thc midlinc. The subjcct rtrust maintain good balancc ancl an ercct trunk posturc. Distancc is recordcd from thc start line to thc hcel of thc leacl limb during the lungc-out position. Thc r.naximaldistancc of 3 trials is recordcd and markcd. Eighty pcrcent of the maximal distancc is calculatedand n.rarkcdwith a piccc of tape as a targct fbr thc scrics of timcd lungcs. Thc subjcct is then asked to complete as many lunges as possiblc in 30 scconds;lungcs lcss than thc 80% mark are not recordcd. If thc subject deviatcs from thc path of motion or takcs an extra stcp, the lunge is not included in the count. Thc involvcd limb is thcn tested,using the 80% rnark fiom the uninvolvcd limb (Figurc l). Step-down, left and right. The step-down is a unilateral test perfonned frorn a platforrn 8 inches(20.32 cm) high. Subjects step forward and down toward the floor. Thc down lirnb only brushes the floor with the heel and thcn rctums to full knee extension.This counts as one repetition. Each repetition must bc cornpletedsuch that the step limb is not used to accelerateback onto the step. The number of repetitionsthe subject performs in 30 secondsis recorded.Both limbs arc tcsted (Figure 2). Single-leg press. Subjectsare positioned on the Total Cyrn (FitnessQuest Inc, Canton, OH) at level 7, which is considcred to be 50% of the subject's body weight. Subjectsbegin with the test kncc in full extension. One repetition consists of a complete cycle of full knee extension to 90' of knee flexion

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extreme right represents severe pain. The marked value was measured with a standard ruler and then converted to a pain score. The VAS has been previouslv validated in the literal u r e 2 {)a n d u s c d i n p a t i e n t sw i t h P F P S . l l Procedure

The University of Kansas Medical Ccnter's InternalReview Board approved the study. Bcfore participating,subjcctswcre screencd with questions rcgarding previous lowcr extrentity injuries. After being selectedto participate,each subjectcompleted an informcd consent form followed by the VAS. Aftcr F igur e 2 , S t e p - d o w n t e st. completing the VAS, thc subject was instructedin the propcr technique for cach of thc functional performancc tests. Thc subjectperformed each ofthe functional testsin random order, and both lower extremitics were tcstcd. The beginningtest lcg was randomly assigncd for thc single-lcg press and thc stcpdown test. Each tcst was perfon.nedonce, without the usc of tapc or a brace. Pain lcvel during the test was ntonitorcd,and subjectswere instructcd that thcy could stop duc to pain, but prin lcvcl wts not a slopping critcrron. Each subjcct bcgan thc assessmcntsessionwith a warnt-up pcriod that consisted of low-resistance,lowcr cxtrcrnrty cycling. Thc task-spccific wantl-up includcd practicc fbr cach F igur e 3 . S i n g l e - l e g p r e ss te st. functional pcrfornrancctcst (3 to 5 rcpctitions with a 30-sccond rcst bcfbrc thc actual tcsting). A writtcn dcscription of each tcst was rcad to thc subjcct, fbllowcd by a dcnronstration of thc test by thc tcstcr (Appcndix). Participantsrcccivcclno vcrbal encouragcmcntduring actual tcsting. Subjcctswcrc allowcd a l-minutc rcst bctwccn functional pcrforrrance tcsts. Reliability. For intraratcrrcliability, l5 subjcctswith PFPS wcrc tcstcd on 2 occasions,48 to 72 hours apart.Thc randorn ordcr of functional tcsting was nratchcd bctwcen day I and day 2. Visual analog scalc scorcshad to match within 0.5 fi'om test clay I to test day 2 (cg, a subjcct who scorcd (r.5 on clay Figure4. Balance-and-reach test. I had to score bctwccn (r.0 ancl 7.0 on clay 2). Pain has nrotivational, affcctivc, cognitivc, bchavioral,and scnsorydirncnand rcturn to full knec cxtcnsion. 'fhc numbcr of unilatcral sions,2land thcsc factorscan hindcr a tcst-rctcstdcsign.Thcrcsquats con.rplctcdin 30 scconds is rccordcd. Both limbs arc forc, for rcliability tcsting, subjcctshad to scorc within 0.5 on thc VAS fiorn tcst day I to tcst day 2 to prcvcnt confounding tcstcd (Figu rc 3 ). Bilateral squat. Sub.jcctsstart this tcst standing with the of the pain variable. C o r r e l a t i o n . T h e s c o r c s o n d a y I o f t h c l 5 r e l i a b i l i ty su b knccs in full extcnsion,shouldcr-widthapart,and wcight cvenly distributcd on both lirnbs. Subjccts lower thcir bodies to a jccts werc addcd to the scores of l4 othcr individuals with kncc position of 90" and thcn rcturn to full extcnsion. One unilatcral PFPS who had complctcd thc VAS and 5 functional rcpctition consistsof a corrrpletccycle of straight standing to tcsts. This infbm.rationwas uscd to establish a rclationshin 90" ofknee flcxion and rcturn to straightstanding.The number bctwcen the VAS and functional tcst scorcs. All sublcct.s scorcdwithin this range except for 2. Both subjcctswcrc askcd of bilatcral squatscompletcd in 30 scconds is recordcd. Balance and reach. The subjectstartsthe test behind a start to return within 48 hours and repcat the VAS. Upon rcturn, I line. The subjcct rcachesstraight forward with one leg so that of thc 2 subjectsscorcd within thc acccptableVAS rangc; the thc hcel touchcs thc flooq with rnost of the body weight re- other did not and was dropped from thc study. Limb Symmetry Index. The PFPS limb scoreswere cornn.rainingon thc back (tcst) leg. The uninvolvcd limb is tested first. Distancc is recordedfrom the start linc to the heel of the p a r e d a n d a n L S I w a s c s t a b l i s h e d . r l T h c g r o u p o f l l su b j ccts lcad limb. The rnaximal distance of 3 trials is recorded and with norn.ralknees also pcrformed thc 5 functional tests to markcd. E,ightypcrcent of the maximal distanceis calculated deterrninethc LSI. and rnarked with a piece of tape. During the 30-secondtest period, thc subjectperforms as many balance-and-reach lunges DataAnalyses as possiblc. Only lunges in which the subject's heel touchcs beyonclthc 80% mark are recorded.The involved limb is thcn We con.rpileddescriptivecharacteristicsfor each subjcctand tested using the 80% mark from the uninvolved limb (Figurc all perfonnance scores in a Microsoft Excel (Microsoft Inc, 4). vcrsion 2000, Redrnond,WA) spreadsheet. Data frorn thc VAS Visual Analog Scale (VAS). A l0-cm horizontal line was were recorded as a single score to one decimal placc. Data uscd to assesspatellofcmoralknee pain over the 24 hours be- from each of the functional pcrformance tests were rccorded tbre the testing pcriod. The far left is "pain free," and the as numbcr of repetitions. We recorded repetitions for right and

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V olum e 37 r N u mb e r 3 o S e o te m b e r2 0 0 2

Table1. IntraraterReliabilityEstimatesfor FunctionalTests Test Anteromedial unge Step down Sin g l e - l e gp r e s s Bil a t e r a ls q u a t Ba l a n c e a n d r e a c h

In tr a cla ssCo r r e la tio n Sta n d ard E rror of Co e fficie n t( 3 ,1 ) th e Mean

82 94

3B

6l

30

79 B3

47 68

RESULTS Reliability Intraclass correlation coefficients and SEMs for thc intratester mean scores are summarized in Table l. Intraclasscorrelation coefficientsranged from .79 to .94, and SEMs rangcd from .38 to .68. The highest ICC was found with the stepdown test and the lowest ICC with the bilateral souat test. Correlation

Table2. PearsonCorrelationCoefficients F u n c t i o n a lT e s t

r Va lu e with Visu a l An al og S cal e

730-

An t e r o m e d i a l u n g e Step down S in g l e - l e gp r e s s Bil a t e r a ls q u a t Ba l a n c e a n d r e a c h

q-7n+

s031 386 461.

.Significant at .05level. at .01 level. f Significant

Thc correlation matrix from the Pearson correlation cocfficicnt analysesis found in Table 2. Corrclation valuesbctwccn thc VAS and thc functional tests ranged from .386 to .730. Only the bilateral-squattcst did not corrclatcsignificantlywith the VAS. Limb Symmetry

Index

Lirnb difference in thc PFPS group was statisticallysignif'icant (P < .013) for all unilatcral functional tcsts. Limb dif-f-erenccin the normal subjccts was not statisticallysignificant for any ofthc unilatcral functional tcsts.The LSI rangcd front lcll anterornediallunge, right and lcft stcp-down,right and lefl 95.lVo to l00.6oh in thc normal group and 80.0% to 89.11%in lcg prcss, bilatcral squat, and right and lcft balancc and rcach. thc PFPS group. SPSS fb r Wind ows ( v c r s ion 10, SPSS I nc , Ch i c a g o , I L ) When comparing thc right lirnb of norrnal subjcctswith thc statistical soflware was uscd to analyzc thc data. Statistical involved limb of thc PFPS group, thc norntal group scorcd significanccwas sct at P < .05. Subjcct charactcristics(age, rnorc rcpctitions on thc stcp-down, lcg prcss, and bilatcral hcight, and weight) werc compared betwecn thc groups using squat. Tcst scores bctwccn groups wcre statisticallydiffcrcnt a 2-sarnplcI tcst. for the stcp-down tcst (P < .013). Reliability. We used thc intraclass corrclation cocfficicnt (lCC) to cvaluatcintraratcrrcliability (lCC 3,I ). Standardcrror of thc mcan (SEM) was calculatcd to dcscribc the prccision D I S C U S S I O N of thc rncasurcmcnt. Functional outcomc rncasurcsshould bc simplc to adrninCorrelation. Corrclation analyscs bctwccn the VAS and istcr, incxpcnsive, rcliablc, and valid. Most of thc functional functional tcsts wcrc cvaluatcd using thc Pcarsoncorrelation tests prcviously reported in thc litcraturc are targetcd to pacocfficicnt. ticnts after anterior cruciatc ligamcnt injury.22Thc purposcof Limb Symmetry Index. Statistical diffcrcncc bctwccn in- our invcstigation was to dctcrmine the intraraterrcliability of cliviclualsubjccts' lirnbs for thc unilatcral functional tcsts was 5 functional pcrfornrancc tcsts. In addition, thc rclationship clctcrn-rincd using a paircd I tcst. Bonfcrroni corrcction was bctween pain and functional tcst scoreswas asscsscd. applicd to thcsc 4 tcsts, sctting thc alpha lcvel to .0514 : Intraratcr rcliability nrcasurcs the consistency of a tcst's 0.013. The statisticaldillercnce between subjccts with PFPS scorc with respectto tin.rcancl thc evaluator.If a changc docs and nomral subjectson functional tcst scorcs was detcrmined occur in the measure, onc can attribute the change to truc with indcpcndent/ tests. Bonf-erronicorrection was applied to changc and not chance. In this study, intraraterreliability was thc sc 4 tcsts, sctting t he alpha lev el t o . 0514: 0. 01 3 . L i m b fair to high with a rangc frorn 0.79 to 0.94. The SEMs for all syrnrnctry indcx was calculatcd with thc fomrula (involvcd/ testswerc lcss than one rcpetition, indicating high prccision.2l uninvolved) x 100 fbr each group. Pain is a common svmDtom of individuals with PFPS.

Table 3. Group Data*

NormalSubjects Test Anteromedial unge Step down S in g l e - l e gp r e s s Bil a t e r a ls q u a t Ba l a n c e a n d r e a c h

Rig h t L im b M e a n ( SEM )

I 1. 60( 0. 54) 17. 80( 1. 02) 13. 80( 1. 25) 19, 6( 0. 91) 16. 4( 1. 46)

LeftLimb M ean( SE M ) 12. 2( 0. 7 0 ) 17. 7 ( 1. 44 ) 14.5(1.26) NA 16.9(1.47)

P atel l ofemoralP ai n S ubi ects

LimbSymmetry I n d e x( %)

l nvol ved Li mb Mean (S E M)

Y3.Z

11.72(0.57)I 13e3 (1.02)t+ 136e (0.87)t

NA 970

16.51 (1 .34) 17.93 (1.03)t

95.1 10 0 . 6

U ni nvol vedLi mb Mean (S E M)

1 3 . 5 6( 0 , 4 8 ) 1 7 . 3 1( 0 . 9 9 ) 1 6 . 0 0( 0 . 8 4 ) NA 1 9 . 9 0( 1 . 0 4 )

Li mb S y mmel ry Index (% )

8 5 .9 800 843 NA 8 9 .8

'SE M i n d i c a t e ss t a n da r d e r r o r o f th e m e a n ; NA, n o t a p p licabl e. f S i g n i f i c a n td i f f e r e n ceb e twe e n lim b s a t P < .0 1 3 . f S i g n i f i c a n t d i f f e r e n ceb e lwe e n g r o u p s a t P < .0 1 3 .

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Therefore, a functional test for this population should correlate somewhat with a pain measure. All unilateral functional tests correlated significantly with the VAS. This finding indicates that these 4 functional tests were sensitiveto changesin pain level. As pain level decreased,the number of rcpetitionsperfonned increased.The bilateral squat correlatcd the lcast with the VAS and resulted in the lowest reliability. This rcsult is probably due to the bilateral nature of the tcst. Bccause weight distribution was not monitored, subjectscould shift weight to the uninvolvcd limb to avoid overloading the involvcd side. The 5 functionaltestswere tcstcd on subjectswith unilateral PFPS and, therefore,we hypothcsizedthat there would be a difference in performancebetwecn thc 2 limbs. For all tests, thc uninvolvcd limb scored higher. Results from the paired t tests reached significance for thc antcror.nediallunge (P < . 013),step -do wn(P < . 013) , leg pr es s( P < 013) , and b a l a n c e and re ach (P < .0 l3 ) . Wc also cornparcdthe involved limbs of thc PFPS group and thc right limbs of thc nomral group. Surprisingly,thc stcpdown was the only test that was significantlydifferent betwccn the PFPS group and the normal group (P < .013). The normal subjccts scorcd more repetitions on the step-down and lcg press but not on the anteromediallungc or balanceand rcach. Both thc anteromcdial lunge and balance-and-reachtcsts rcquirc sornework from both linrbs, and this may interfcrc with a dif-fcrcntialscorc. Sincc only thc stcp-down tcst was significantly different bctwccn groups, pcrhaps the LSI is a bcttcr indicator of PFPS cliscrinrination.Thc LSI has bccn dcscribed in thc litcraturcas a rcturn-to-sportcriterion. Barbcr ct alrl suggestedan LSI of 85'% as a satisfactory lcvel for dctcrmining norntalcy in thc paticnt. For thc 5 antcrior cruciatc ligan'rcnt-reconstructcd PFI'}Sfirnctionaltcsts,the LSI rangcd frorn 80.0'Zoin thc stcpdown to U9.tt% in thc balancc and reach. Thc nonr.ralgroup avcragcd95% fbr thc unilatcral tcsts. Bccausc PFPS is so variablc ancl function dcpcnds on thc prcscncc of pain, a highcr LSI of 93 to 95u/ofor cach functional tcst Inay bc a bcttcr prcclictorof norrnalcy in this patient population. Becausconly intraratcrrcliability was statisticallytested in this study, thc rcsultscannot bc gencralizcdto othcr clinicians. Furthcr work is undcrway to determincthc intcrratcrreliability and scnsitivity of thcse 5 functional tcsts bctbre and aflcr rchabilitation.Clinically, wc have notcd that subjcctswith PFPS irnprovc on all the functional tcst scorcsand incrcasctheir LSI as thcy progrcssthrough rehabilitation.

C O NCLUSIONS Thc purposc of our study was to investigatethe intrarater rcliability of 5 functional performancetests.The intraraterreliability proved to be fair to high, with the highest reliability occurring with thc step-down test and the lowest with thc bilateral squat. The unilatcral functional tests correlatedsignificantly with the visual analog scale and differentiatedbetween the involved and uninvolved extren.rities.Howeveq the limb symmetry index is probably a better discrirninatorof patcllof'en.roralpain syndrornethan the absolute number of repctitions obtained on cach test. The key to the reliability of thc tests is that the clinician follow standardprotocol. Further reliability testing among clinicians needs to be investigated. The functional tests are designedto be uscd independently or together. Each test has a particular, unique contribution to the total functional picture. For patients who are unable to

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2002 Volume37 . Number3 . September

tolerate a single-leg squat, the single-legpress can bc used to assessquadriceps function. As patients progress, the following 3 tests can be used: (l) the step-down requires balance and eccentriccontrol of the quadriceps,(2) the anteromediallungc requires a greater range of knee flexion, and (3) the balance and rcach requires single-leg balance,lirnb stability, and proprioception. Before discharge, a patient with patellofemoral dysfunctionshould be able to complete the unilateraltestswith the involved limb and score within l0o/o of the uninvolved limb.

ACKNOWLEDGMENTS This study was funded by thc American PhysicalTherapyAssociationSportsPhysicalTherapyScction'sSmallGrantProgram. REFERENCES l. MarianiPP,Caruso I. An electronryographic investigzrtion ofsubluxation ofthc patel l a.J l l ona.Joi ntS urgB r. 1979;61:169l 7l . l C , Worrel lTW. A ntcri orkneepai nsyndromc: rol eof t hc v as tus 2. Wcstl al D mcdi afi sobl i que.J S portl l chubi l . 1992:'l :311325. syndrome.In: 3. Ficat RP Latcral lascia releascand latcral hypcrpressure Pickett JC, Radin IlL, ctls. Chondronutlut'iaol tha Putellu. Baltimore, MD : Wrl l i ams& Wi l ki nsl l 98l :95 l l 2. 4. Grcenfi cl dMA , S cottWN . A rthroscopi cval c uati onand trcatmc ntol ' thc patcllolcnroraljoint. Orthop CIin North lm. 1992,23:587600. patcl l ai n the adol escent. In: K c nnc dy 5. JamesS L. fl hondrorral aciof'thc a JC, cd. Thc IniuraclrldolasccntKncc. Baltimore,MD: Williams & Wilki nsl 1979:205251. 6. KannusP, Nittymaki S. Which firckrrspredictoutcornein thc nonopcrativc treatmcntol'patellol'cmoralpain syndrorne'lA prospcctivclirllow-up study. Mad Sci Sports Excrc. 11994:'26:289 296. l acxi st'/In: P i ckel tJC , R adi nt]L, 7. R adi n[rL. D oeschondrornal acipatcl a gJs.Chondrontuluciu o/ tha Putallu.IJtrltintotc,MD: Williarns& Wilkins; 1983:6882. 8. P ostMD , Ful kcl sonMD . K nce pai n di agrams:conel ati onw i th phy s i c al cxaminationfindings in patientswith arrlcriorkncc pain. Arlhnt.scttp.v. 1994:l 0:618 623. pai n syndrorncs: 9. Mal ck MM, Mangi ncl l l i . P atcl l ofcrnoral a comprc l rc nsivc and conservativeapproach..l Orlhop Sport.sPh.vslhcr. l98l;2:108 I 16. nt of l l ncti onal tcstsafl cr antc ri or 10. I{i sbcrgMA , U kel andA . A sscssme 217. cruciatcligamcntsurgery.,l Orthr4tSport"-Phys Thar. 1994:'19:'212 l l . B arberS D , N oycs FR , Mrngi nc R l l , McC l oskcyJW, H artmanW . Quantitativc asscssmcnt of lirnctionallrmitationin nonnal zrndantcriorcruciatc 214. ligarrcnt-dcficicntknees.C/in Orrhop. 1990;255.2.01 12. B ol gl a LA , K eskul aD Il .. ttcl i abi l i tyof l ow er extremi tyf uncti onalpc rlrrnrance tests.J Orthop Sports PhysI-hcr. t991,26:138 142. 13. C hesw orthtsM, C ul ham E G, Tata GE , P cat M. V al i dati onof oul c onre rneasLrres in patientswith patellofernoralsyndnrnre. ,l Oilfu4t SportsPhvs Il cr 1989:10:302 308. mus c l e 14. R ei l l y D T, MartensM. E xpcri mcntalanal ysi sof the quadri c c ps joint reactionforce lbr variousactivities.,'lcla force and patellol-emoral Orthop Scund. 1972 43:126 131. 15. Gray GW. Lower ExtremityFunttional Pro/tla. Adrian,MI: Wynn Marketi ngInc; 1995. l ae.C un A thl 7'hcrA ,ssrsc./. l 9 [t2;8:13 16. R ei d D C . C hondromal acipatel a 20. als orders : 17. Wi l k K E , D avi esGJ, Mangi neR E , Mal oneTR . P atel l ofemordi lisystemand cl i nrcalgui del i nesfor nonoperati vrehabi e a cl assi fi cati on tation. -/ Orthop Sports Phys Thcr. 1998,28:307 322. l ae:r pros pec ti v e a 18. Insal l J, Fal vo K A , Wi se D W C hondromal acipatel study..l B one.l oi rttS urg,4rr. 1976;58:l 8. l ae: a surveyconduc ted 19. R obi nsonA R , D arracottJ. C hondromal acipatel a at the Anny Medical RehabilitatronUnit, Chester.lnn Phys Mad. 19101' I 0:286-290. B . The val i dati onof v i s ual 20. P ri ceD D , McGrathP A , R afi i A , B ucki ngharn

analoguescalesas ratio scalemeasuresfor chronicand experimental pain. Pain. 1983:l'7:45-56. 21 . M e l z a c kR . P a i n :an o ve r vie w.Acta An a e sth e sioSca l n d .1999:43;880884. 22. LephartSM, PerrinDH, Fu FH, Minger K. Functionalperfonnancetests for the anteriorcruciateligamentinsuflicicnt athlete.Athl Train J Natl A r h l h n i n A s s o c .19 9 l:2 6 :4 45 0 . 23. PorrneyLG, WatkinsMP.FoundatknsoJ Clinital Resaurch.-Applicattuns lo Pre('ticc.Norwalk, CT: Appleton and Lange; 1993,

APPENDIX Instructionfor FunctionalPerformanceTests l. Anteromedial lunge: "You will stand behind a staft line and pcrform 3 lunges with the uninvolvcd lirnb. The maxir.nunrdistanceachievcd will be used to calculatethe 80% targct distance.Thc targct distancewill bc marked on thc floor with tape and recorded on the data form. Then, you will stand with your feet straddling thc rniddle line. Your toes must stay behind the central linc. Thcn, you will step out with your - leg so that your hccl passesthe rnarked distancc (tester will demonstrate).You will continue thc lunges for 30 scconds.Do you havc any questions'/" Criteria: Only lunges in which thc subjcct'shecl touchcs bcyond thc 80% lnark will bc rccorded. 2. Step-down: "You will stand on this S-inch stcp with both lcgs. Whcn I say go, you will lower your - lcg so that your hccl touches thc ground. You will thcn rcturn this lcg to the platforrn and touch the top of thc platform. You will continuc this scqucncc until I say stop. Thc test is run for 30 scconds. Do not push off thc ground as you lowcr your hccl. Do you havc any qucstions?" Criteria: Hccl must make contact with a slight hcsitation

both at the down phase and the start phase. Do not allow the subjects to vault up with their touch leg. 3. Single-leg press: "You will start with your back against the sled and your knees fully extended. Place your feet hip-width apaft on the standing platform. When I say go, you will bend your - knee and lower your body on the sled to approximately 90o of knee flexion. I will tell you when you achieved the appropriateknce bend. You will continue performing the knee bends for 30 seconds.Do you have any questions?" Criteria: Foot must remain flat on the Total Gym platfomr, no vaulting. Full 90" must be achieved(slcd must touch platforrn). Bilateral squat: "You will stand with your f'ccthip-width apart and squat down so that your knees bend to 90" like this (tester dcmonstratcs).Your scat will touch this chair. Do not rest on the chair. You will rcturn to the start position and repeatthis activity for 30 seconds.Do you havc any questions?" Criteria: Buttock must touch scat.Subjectrnustrcach full s t a n d i n gw i t h f u l l k n c c c x t c n s i o n . B a l a n c e a n d r e a c h : " Y o u w i l l s t a n d b e h i n d a sta r t l i n c and pcrform 3 lungcs with thc uninvolved lirnb. The maximum distanccachieved will be used to calculatcthe tl0,% targct distancc.Thc target distancewill be markcd on thc floor with tapc and rccorded on thc data form. Stand with your feet straddling thc middle linc. Your tocs must stay bchind thc central linc. You will stcp out with your _ lcg so that your hecl passesthe markcd distancc(tcstcr will dcmonstrate).Do not rest your foot down whcn you reach the targct distance.You will continuc thc reachestbr 30 scconds.Do you havc any qucstions?" Criteria: Only rcachcsin which thc subjcct'shccl touchcs beyond the 80% mark will bc rccordcd.

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