Are patellofemoral pain and qs muscle torque associated with locomotor function
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  • 1. Are Patellofemoral Pain and Quadriceps Femoris Muscle Torque Associated With Locomotor Function? Background and Purpose. The purpose of this investigation was to determine the influence of pain and muscle weakness on gait variables in subjects with patellofemoral pain (PFP). Subjects. Nineteen female subjects with a diagnosis of PFP and 19 female subjects without PFP participated in the study. Methods. Subjects underwent gait analysis (stride characteristics and joint motion) during level walking, ascend- ing and descending stairs, and ascending and descending ramps, in addition to isometric torque testing of the knee extensors of the involved limb. Pain and functional status also were assessed. Results. Compared with the comparison group, the primary gait compensation in the PFP group was a reduced walking speed, which was a function of both a reduced stride length and cadence. Knee extensor torque was the only predictor of gait function, with increased torque correlating with improved stride characteristics. In addition, PFP was not associ- ated with locomotor function. Conclusion and Discussion. These findings suggest that functional ability in persons with PFP is associated with increased quadriceps femoris muscle torque. Future research is needed to determine whether function improves with quadriceps femoris muscle strengthening. [Powers CM, Perry J, Hsu A, Hislop HJ. Are patellofemoral pain and quadriceps femoris muscle torque associ- ated with locomotor function? Phys Ther. 1997;77:1063-1078.1Key Words: Gait, Patellofemoral pain, Quadriceps femoris muscle torque.Christopher M Powers IJacquelin PemyArthur HsuHelen J HislopPhysical Therapy . Volume 77 . Number 10 . October 1997
  • 2. uring the stance phase of gait, the knee isD in inhibition of alpha motoneurons in the anterior horn believed to be the principal determinant of of the spinal cord.%lthough in clinical practice pain limb stability. The quadriceps femoris mus- and inhibition have been associated,14decreased motor cles act as the primary stabilizers of the knee, unit recruitment of the quadriceps femoris muscleespecially during loading response, when the knee flex- appears to be linked to knee joint e f f ~ s i o n ~ ~ ~ ~ " ~ ~ion moment is the g r e a t e ~ tActivity of these muscles is .~ and has been reported to be independent of pain.I2,l"necessary to support the flexed knee posture." Young et all7 reported that afferent block by local anesthesia was not effective in reducing quadricepsReduced knee flexion during loading response is gener- femoris muscle inhibition, despite a complete reductionally thought to be an action aimed at limitingjoint forces in pain. Additionally, Stratford12 did not observe aand may be indicative of knee pathology. For example, relationship between pain and inhibition that wouldpain and weakness are commonly associated with patel- explain reduced electromyographic activity of the quad-lofemoral joint p a t h ~ l o g y and the avoidance of knee ,~ riceps femoris muscle during a maximal isometric con-flexion during stance has been found in persons with traction in persons with acutely effused knees. In con-patellofemoral joint pathology.~erchuck a16 used the et trast, deAndrade and colleagues15 presented evidenceterm "quadriceps avoidance pattern" for persons with that pain reduction through lidocaine injection reducedanterior cruciate ligament (ACL) deficiency to describe quadriceps femoris muscle inhibition in knees that werea gait pattern that minimizes the knee flexion moment artificially distended. These observations, however, wereduring the loading response and therefore the demand made on only four subjects.of the knee extensors. Persons with PFP also may adopta similar strategy to reduce the patellofemoral joint Despite the current state of knowledge regarding thereaction forces associated with increased knee flexion cause of quadriceps femoris muscle inhibition, manyand quadriceps femoris muscle activity. A quadriceps functionally related questions remain. For example, arefemoris muscle avoidance pattern could be deleterious compensatory gait patterns a result of pain, weakness, orto the patient with PFP, however, if further quadriceps both? Do gait adaptations associated with patellofemoralfemoris muscle atrophy results from disuse. This avoid- joint pathology differ among persons with varyingance pattern may contribute to patellar instability, which degrees of pain? What is the relationship between PFPis commonly believed to be at least partly the result of and quadriceps femoris muscle weakness? The purposeweakened dynamic stabilizer^.^.^.^ of our investigation was to determine the influence of PFP and quadriceps femoris muscle weakness on strideAlthough gait patterns have been described for various characteristics and the amount of knee flexion duringknee pathologies such as degenerative joint di~ease,.~~the loading response in different gait conditions (levelrheumatoid arthritis,"-l1 and ACL insufficiency,~ittle is walking, ascending and descending stairs, ascending andknown about subjects with PFP and the relationship descending ramps). Functional assessment scores werebetween pain and weakness. The relationship between also correlated with actual gait characteristics. Weknee pain and quadriceps femoris muscle inhibition, hypothesized that there would be a correlation betweenhowever, has been discussed previously in the literature. either pain or quadriceps femoris muscle weakness andReflex inhibition has been demonstrated in subjects with the limitations in gait function associated with PFP. Thisknee pathology12and is reported to occur when afferent information could assist in identifying variables associ-stimuli from receptors in or around the knee joint result ated with gait limitations in this population and couldCM Powers, PhD, PT, is Assistant Professor, Department of Biokinesiology and Physical Therapy, University of Southern California, 1.540 E AlcazarSt, CHP 135, Los Angeles, CA 90033 (USA) (powers@hsc.usc.ed~~). Address all correspondence to Dr Powers.J Perry, MD, is Chief, Pathokinesiology Service, Rancho Los Amigos Medical Center. Downey, Calif. and Professor, Departrnent of Biokinesiologand Physical Therapy, University of Southern California, Los Angeles.A Hsu, PhD, PT, is Assistant Professor, Departrnent of Biokinesiology and Physical Therapy, University of Southern California, 1.0s i2ngeles.HJ Hislop, PhD, PT, FAPTA, is Professor and Chair, Department of Biokinesiology and Physical Therapy, University of Southern California, L.osAngeles.This study was approved for human subjects by the Los Amigos Research and Education Institute Inc of Rancho 1.0s Amigos Medical Center.This study was supported in part by a grant from the Foundatiori f i ~ Physical Therapy IIIC. r nrtic.1~ submittpd August 8, 1996, nnd runs occc?t(.cl April 25, 199%Thi~ ruas1064 . Powers et al Physical Therapy . Volume 77 . Number 1 0 . October 1997
  • 3. Table 1. with PFP, and they had no other limitations that wouldSubiect Characteristics alter their gait. PFPa Group Comparison Group (n= 1 9) (n= 19) P Isometric knee extensor torque was recorded using a Age (YI Lido d y n a ~ ~ ~ o m e tPrior to testing, compensation for er.* X 25.4 27.5 limb weight and the effects of gravity was made automat- SD 8.2 4.7 .35 ically by the dynamometers computer software program Range 14-46 23-3 8 (Version 3.8, 1989). Reliability of the data used for H c g h t (cm) correction was not assessed. Torque data were recorded X 165.1 165.3 by a DEC 11/23 computert at a rate of 2,500 Hz. The SD 7.6 7.7 .94 Range 151 .l-177.2 149.9-183.5 DEC computer was interfaced with the dynamometer. W e i g h t (kg) X 62.4 59.2 Knee pain was recorded using a visual analog pain scale SD 9.3 7.5 .25 (VAS). The VAS consisted of a 10-cm horizontal line, the Range 42.0-82.7 46.8-74.1 ends of which defined the minimum ("no pain") and maximum ("extreme pain") of perceived pain. Each s u b ject placed a mark on the line to indicate the intensity of pain. The amount of pain indicated on the line wasaitl in guiding treatment programs aimed at improving converted to a numerical value based on the distance (infunction. centimeters) from the minimal possible pain to the mark on the line. The VL4S been shown by Chesworth et allx hasMethod to be a valid indicator of pain changes in patients with PFP. Subjects To evaluate symptoins and functional limitations in theNineteen female sul~jects between the ages of 14 and 46 subjects with PFP, a functional assessment questionnaireyears with a diagnosis of PFP participated in this study (FAQ developed by Kujala et all was used. The validity (Tall. 1). Subjects were recruited fi-om the Southern and reliability of measurelnents obtained with the FAQCaliforr~iaOrthopaedic Institute (Van Nuys, Calif) and have not been reported. This questionnaire containedwere scl-eened to rule out ligamentous instability, inter- 13 multiple-choice questions relating to patellofemoralnal der;angement, and patellar tendinitis. In addition, joint symptoms. Scoring was based on a numerical scalesul~jects not have any other orthopedic or neurologic did depending on question response, with some items beingimpairments, as determined by physical examination weighted more than others. The maximum possibleand questionnaire, that would adversely affect gait. Each score was 100, which represented no pain aild nosut!ject:s pain originated from the patellofemoral joint functional deficits. This scoring system has been demon- (as determined through their complaints and a physical strated to differentiate between different classificationsexatnination), and only patients with histories relating to of patellofemoral disorders.l0overuse (ie, symptoms related to repetitive activity) orinsidious onset were accepted. The physical examination Stride characteristics were recorded with a micro-consisted of passive range of motion, active range of processor-based Footswitch Stride Analyzer system.:motion, palpation of the patella and related structures, This system consisted of compression-closing foot-and a patellar grind test. In addition, each subjects pain switches taped to the soles of the subjects bare feet. Thewas readily reproducible with at least two of the follow- footswitches contained sensors at the heel, the first anding acthities: stair ascent or descent, squatting, kneeling, fifth metatarsal heads, and the great toe that respondedprolonged sitting, or isometric quadriceps femoris mus- to compressive loads equal to o r greater than 3 psi.cle contraction. The subjects with PFP were varied with Stride characteristics calculated from this system includ-respect to the severity and duration of symptoms. Sub- ed: speed, stride length, cadence, single- and double-jects were excluded from the study if they reported limb support times, and stance and swing durations.ha~ing either knee surgery or acute traumatic patellardislocation. Sagittal-plane motion of the ankle, knee, and hip joints was measured with a Vicon motion analysis system.s SixNineteen female subjects between the ages of 23 and 38years served as a comparison group (Tab. 1). Thesesubjects had no history or diagnosis of knee pathology ortrauma, and they were free of any current knee pain. In 1.oredan Biomedical Ill,-, 16.12 Ua lnci (:t, PO Box 1154, Davis. (:A 95617.adtlitior~, these subjects did not report discomfort with Digiral quipment C o ~ p 146 Main St, Maynalrl, MA 01754. , B&1. E:ngincer-~ng,8807 Pioneel Blvd, Suitr (:. Snt~ta Springs. (1% 90670. Fcany of the activities described as criteria for the subjects Oxli~rd Mctrica Unit 14, 7 Weat Way, Botlry. O x h ~ l d , Etlgla~ldOX:! OUR.Physical Therapy . Volume 77 . N u m b e r 10 . O c t o b e r 1997 Powers et al . 1065
  • 4. infrared cameras operating at a 50-HT sampling rate walking, subjects were instructed to walk at their normalwere used. speed. For fast walking, subjects were instructed to walk at a speed as if they were in a hurry. Joint motion andA 10-m walkway was used for free- and fast-walking trials, stride characteristics were then assessed simultaneouslywith data being collected over the middle 6 m. Analysis during free and fast level walking, ascending andof stair use was done with a four-step staircase with a descending stairs, and ascending and descending ramps.slope of 33.7 degrees, a step height of 20.3 cm, and atread depth of 30.5 cm. Ramp walking was assessed with Data Analysisa 12-degree incline that was 6.1 nl in length. Sagittal-joint motion of the ankle, knee, and hip was calculated for all conditions tested. Raw motion dataProcedure were filtered at 6 HL using a fourth-order, ButterworthAll data collection was performed at the Pathokinesiol- recursive filter." The data were then digitized andogy Laboratory, Rancho Los Amigos Medical Center, linearly interpolated to 0.01-second intervals. The stanceDowney, Calif. Before testing, all procedures were phase of each stride of motion collected Ivas normalizedexplained to each subject and informed consent was LO 62% of the gait cycle in order to average data fromobtained. Subjects were then asked to complete the FAQ m ~ ~ l t i p strides and different subjects. We believe this lebased on their current symptoms and limitations. value to be representative of normal walking,[ and it was consistent with the average stance phase deinonstratedPrior to gait analysis, maximal isometric knee extensor by our subjects for all conditions. Maxirnuni and rnini-torque and knee pain were measured. Subjects were mum motion for each joint were analyzed for each phaseseated on the Lido dynamometer chair with the hips of the gait cycle. Analog signals obtained from theflcxed to 90 degrees and the knee flexed to 60 degrees. individual footswitch sensors were synchronized with theThe axis of rotation of the dynamometer was then motion data and were used as event markers to deter-positioned in line with the axis of rotation of the knce, mine the different phases of the gait cycle.with the resistance arm cuff placed just proximal to themalleoli. A Velcro@strap1was placed across the pelvis to Torque data were integrated at 0.1-second intervals. Thee n w r e proper stabilization. Sixty degrees of knee flexion torque produced by the limb weight (as determined bywas used because this position has been found to result the gravity cornpcnsation test) was added to the rawin the greatest torque output in female subjects without torque to account for the effects of gravity. The greatestinlpairment~.~) value over the 5-second trial was recorded for each subject. T o control for the cffkcts of subject size, a11Isometric torque during a 5-second maximal contraction torque data were normalized by body weight andwas then recorded. Verbal encol~ragement was given to expressed in newton-meters per kilogram.all sub.jects during the trial. After torque was measured,the subjects with PFP were asked to rate, using the VAS, The BMDP statistical software was used for all datatheir knee pain during the maximal contraction. Our analyses. The data were tested for normality of distribu-rationale for assessing pain during contraction rather tion using the Wilks-Shapiro W statistic. All significancethan during the locomotor tasks was that we expected levels were set at P<.05.that pain scores obtained during ambulation would notreflect true symptoms. We believed that the subjects Subject characteristics (age, height, and weight) werewould most likely adopt gait strategies to reduce or compared between groups using two-sample t tests.eliminate pain. Comparison of isometric torque values between groups also was made using a two-sample 1 tcst.Following the torque and pain assessment, subjects wereprepared for gait analysis. Footswitches were taped to T o determine whether w i d e charactcristics differedboth of the subjects bare feet, and the reflective rnarkers between groups and conditions, a 2 X 6 (group Xthat were used to determine sagittal-plane motion were condition) two-way analysis of variance (ANOVA) forplaced at the designated landmarks (posterior heel, fifth repeated measures on one variable (condition) wasmetatarsal head, dorsum of the foot, medial and lateral performed. This analysis was repeated for each stridemalleoli, anterior tibia, medial and lateral fe~noralepi- characteristic. Data for stride length and cadence duringcondyles, anterior thigh, greater trochanter, bilateral stair amhulation were omitted from thc analysis due toanterior superior iliac spines, and sacrum). One practice the limitation imposed o n these variables as :i result oftrial of both free and fast walking allowed the subjects to the fixed ctair height and depth. Peak motion at eachbeconle familiar with the instrumentation. For free r l c ~ - oLS4 Inc, P C ) Box 5218, 406 BI.OM.II v r , M d ~ l c h r ~ r lN11 0::lOX h -,1066 . Powers et a1 Physical Therapy . Volume 77 . Number 1 0 . October 1 9 9 7
  • 5. Table 2. Table 3.Moximurr Knee Extension Torque (Normalized by Body Weight) Individual Volues for Knee Extension Torque, Visuol Analog Poin Scale (VAS), ond Functional Assessment Q ~ e s t i o n n o i r e (FAQ) for ~ Subiects With Patellofemorol Pain PFPa Group Camparison Group Tocque (N.m/kg) Knee Extension VAS (1 0= FAQ ( 1 00= Subject Torque Maximum Maximum 0.78 0.69 .03 No. (Nem/kg) Pain) Function) Range 1.28-3.92 1.96-4.02 1 2.54 8.6 53" pain. PFP=~x~tc~llofe~~~o~~~il 2 2.09 7.6 35 3 1.45 9.6 37 4 3.90 6.5 70joint also was compared between groups and conditions 5 1.43 3.4 85using a 2 x 6 (group x condition) two-way ANOVA for 6 2.14 0 73repeated measures. This analysis was repeated for each 7 2.74 4.1 84 8 1.78 4.8 73phase of the gait cycle. 9 2.2 1 0.2 73 10 1.23 6.8 38To assess the association among PFP, quadriceps femoris 11 2.73 0.8 73muscle torque, and FAQ score, we used the Pearson 12 1.79 1.1 75product-moment correlation coefficient. We used sepa- 13 1.23 3.2 62 14 3.16 5.1 68rate analyses to assess the linear relationship between 15 2.42 0 100PFP and torque, PFP and FAQ score, and torque and 16 2.21 8.6 45FAQ score. 17 2.92 6.4 83 18 3.64 3.8 74Stepwise regression analyses were performed to deter- 19 3.48 3.0 82 -mine whether any of the independent variables (pain, X 2.35 4.4 67.5quadriceps femoris muscle torque, or FAQ score) were SD 0.78 3.1 18.1 . .predictive of any of the stride characteristics or thealnount of knee flexion during loading response ... .(dependent variables). This analysis was performed for 100 8the subjects with PFP only and was repeated for all sixwalking conditions.Results .Relationship Among Knee Extensor Torque, Pain, andFunctional Assessment ScoreAfter normalizing by body weight, the maximum kneeextensol- torque of the PFP group was less than that ofthe cornparison group (2.35 N-m/kg versus 3.04 OI 40 -- . . 20 IN.m/kg, P c . 0 5 ) (Tab. 2). During the maximal isomet- 0 2 4 6 8 10ric test, the PFP group reported an average pain level of4.4 out of 10 on the VAS (Tab. 3 ) . The mean score o n VISUAL ANALOG PAIN SCOREthe FAQ for the PFP group was 67.5 out of a possible 100 Figure 1.(Tab. 3 ) . Correlation behveen functional assessment questionnaire (FAQ) score and visual analog pain score for subiects with patellofemoral poin (n=19, r =.72, P<.001).The VAS pain score was not correlated with knee exten-sor torque in the PFP group ( r =.03). In addition, kneeextensor torque was not correlated with the FAQ score cadeilce and in stride length when the data were aver-( r = .25). The VAS pain score, however, demonstrated a aged across all conditions (except data for ascendingcorrelation with the FAQscore in the PFP group ( r = . 7 2 , and descending stairs, which were omitted from theP<.001:1 (Fig. 1). analysis) (Figs. 3, 4). In general, the PFP group demon- strated decreased values for these stride characteristicsStride Characteristics cornpared with the other group.There was a difference between the PFP and comparisongroups for walking speed when the data were averaged The average walking speed of the PFP group (for allacross all conditions (significant group effect, no inter- conditions) was 81% of the average walking speed of theaction) (Fig. 2). Similarly, there was a difference in cornparison group (56.5 m/rnin versus 69.7 m/min,Physical Therapy . Volume 7 7 . Number 10 . October 1997 Powers et al . 1067
  • 6. FR FT AS DS AR DR Condition , Comparison Group ,, - PFP GroupFigure 2.Mean walking speed for subiects with patellofemoral pain [PFP group, n= 19) and subjects without patellofemoral pain (comparison group, n= 19)for all conditions tested. Mean walking speed was lower for the PFP group than for the comparison group when averaged across all conditions(P<.001). FR=free walking, FT=fast walking, AS=ascending stairs, DS=descending stairs, AR=ascending ramps, DR=descending ramps.P<.001) (Fig. 2). The average stride length of the PFP Joint Motiongroup across all conditions was 88% of the average stride There was a significant group effect and a significantlength of the comparison group (1.22 m versus 1.38 m, interaction for ankle joint motion during the terminalP<.001) (Fig. 3). Cadence of the PFP group was 91% of stance phase of gait. When conditions were analyzedthat of the comparison group when averaged across all separately between the two groups, the PFP groupconditions (114.1 steps/min versus 125.2 steps/min, demonstrated greater ankle dorsiflexion compared withP<.001) (Fig. 4). There were n o differences between the other group for fast walking (9.9" versus 7.0".groups for time spent in single-limb support, double- P<.05), descending stairs (27.6" versus 18.g0,P<.001),limb support, swing, and stance. and descending ramps (15.8" versus 1l.gO,P<.01) (Fig. 5 ) . No other differences for ankle motion were found.Of the three variables measured (pain, torque, and FAQ There were n o differences in knee motion betweenscore), knee extensor torque was the only predictor of groups for any phase of the gait cycle, regardless of thespeed, with higher torque values being associated with condition (Fig. 6 ) . Similarly, hip joint motion was nothigher walking speeds. This association was evident for different between groups, regardless of the condition,five of the six conditions (free walking: r=.59, P<.05; for any phase of the gait cycle (Fig. 7).fast walking: r =.59, P<.05; ascending stairs: r z.50,P<.05; ascending ramps: r = .62, P<.05; descending Pain, quadriceps femoris muscle torque, and FAQ scoreramps: r=.67, P<.05) (Tab. 4). Knee extensor torque were not predictors of the amount of knee flexionalso was the only predictor of stride length for four of during loading response. This finding was consistent forthe six conditions (free walking: r=.73, PC.05; fast all conditions tested.walking: r = .61, P<.05; ascending ramps: r = .62, P< .05;descending ramps: r =.76, P < . 0 5 ) (Tab. 4). No other Discussionassociations were found between any of the three vari- We found a decrease in knee extensor torque in the PFPables and the remaining stride characteristics. group (77% of the knee extension torque of the com-1068 . Powers et al Physical Therapy. Volume 77 . Number 10 . October 1997
  • 7. 1.8 1.6 1.4 . g 1.2 5 P a 1.0 $ 0.8 .- L 0.6 0. 84 0.2 0.0 FR FT AR DR Condition Comparison PFP Group GroupFigure 3.Mean stride length for subiects with patellofemoral pain (PFP group, n= 19) and subiects without patellofemoral pain (comparison group, n= 19) forlevel and ramp walking conditions (stairclimbing data omitted due to the limitations imposed as a result of the fixed stair height and depth).Mean stride length was lower for the PFP group than for the comparison group when averaged across all conditions (P<.001). FR=free walking,FT=fast walking, AR=ascending ramps, DR=descending ramps.parison group), as well as an average pain score of 4.4 we did not assess swelling, we cannot determine whetherout of a possible 10 during testing. These associated this really occurred. None of the subjects with PEP,findings suggest that pain may have played a role in however, demonstrated gross joint effusion.reducing quadriceps femoris muscle torque. When painwas correlated with knee extensor torque, however, this An alternative explanation for the lack of a correlationinference did not hold true. These two variables between pain and quadriceps femoris muscle torqueappeared to be completely independent of one another could be related to the testing position used to elicit(r=.03). This finding would imply that knee extensor knee pain. Our procedure assessed the maximum iso-torque was not affected by pain, which is consistent with metric knee extension torque at 60 degrees of flexion,the observations of Stratford" and Young et al." which placed the quadriceps femoris muscle at its great- est length-tension advantage2" but may have been inad-The lack of an association between knee extensor torque equate in reproducing the amount of patellar pain thatand pain may have been related to numerous factors. would inhibit normal function. Although the high quad-For example, patients dealing with persistent pain might riceps femoris muscle forces produced at this kneetend to protect themselves during an activity in which flexion angle also would have resulted in substantialthey would expect to experience pain. Possibly, in order patellofemoral joint reaction forces,"he modest painto avoid pain, patients would not produce a maximum scores reported by our subjects suggest that this com-torque value that truly reflects their strength. This pression was reasonably tolerated. These relatively lowconcept is supported by the fact that 5 of the 19 subjects hain scores may have bken the result of the increase inwith PEP reported little or no pain during the maximal contact surface area between the patella and femur,isometric quadriceps femoris muscle test. Furthermore, which has been reported by Mathews and colleagues" toinhibition of quadriceps femoris muscle activity as a be approximately 40% more at 60 degrees of kneeresult c~feffusion also could have contributed to the flexion as compared with 15 degrees of flexion.reduction in quadriceps femoris muscle torque. Because Increased contact area would have reduced the jointPhysical Therapy . Volume 77 . Number 10 . October 1997 Powers et al . 1069
  • 8. 160.0 140.0 120.0 h .- c < V) P 100.0 a, + 80.0 a, 0 C a, 60.0 3 0 40.0 20.0 0.0 FR FT AR DR Condition pFp Group GroupFigure 4.Mean cadence for subjects with patellofemoral pain (PFP group, n= 19) and subiects without patellofemoral pain (comparison group, n= 19) for levelwalking and ramp walking conditions (stair-climbingdata omitted due to the limitations imposed as a result of the fixed stair height and depth). Meancadence was lower for the P P group than for the comparison group when averaged across all conditions (P<.001). FR=free walking, FT=fast Fwalking, AR=ascending ramps, DR=descending pressure, as the joint forces would have been Table 4- Stepwise Regression Results for Predicting Walking Speed, Stridedistributed over a greater area. In addition, because PFP Length, and Cadencehas been linked to patellar s ~ b l u x a t i o n * ~ because andpatellar subluxation has been shown radiographically to Stride Independent Variableoccur at angles of less than S degrees of knee flexion,?" O Conditiona Characteristic (Predictor) r"it is possible that testing the subjects with the knee lessflexed (ie, 0"-SO0) would have yielded greater pain FR Walking speed Knee extension torque .59 FT Walking speed Knee extension torque .59scores. This position, however, would have placed the AS Walking speed Knee extension torque .50quadriceps femoris muscle at a mechanical disadvan- DS Walking speed Nonetage" and therefore would have resulted in lower torque AR Walking speed Knee extension torque .62values. Given this paradox between testing position and DR Walking speed Knee extension torque .67the pain-torque relationship, as well as the need to assess FR Stride length Knee extension torque .73 FT Stride length Knee extension torque .6 1both variables simultaneously for correlation purposes, AR Stride length Knee extension torque .62we believe that it is not surprising that no relationship AR Stride length Knee extension torque .76was found. FR Cadence None FT Cadence NoneAn inverse linear association was found between pain AR Cadence None DR Cadence Noneand the FAQ score, indicating that the FAQ may besensitive to individual pain levels. The fact that many of " FR=t~ee walk~ng,FT=fayt ~ a l k l n g AS=asrendrng talrs, DS=descendlng , stairs, AR=ascending ramps, DK=descrnding ramps. Stride lerlgth andthe FAQ questions related to the reproduction of symp- cadrnre for ascending and descending staira omitted due to the linritationstoms may explain the correlation between these two the fixed stair u and deDth,scores. Care must be taken in interpreting these results, "AH rzalues significant at the P<.05 level. Ellipsis ind~catesnot applicable.however, as we did not assess pain during functionalactivities. Whether the pain associated with the maximalisometric quadriceps femoris muscle contraction has a1070 . Powers et a1 Physical Therapy . Volume 7 7 . Number 10 . October 1997
  • 9. 30- I -30- I 20- I I -ao-- I I -C 10- I .- -a~-- a~-- I I . -30- I 30 I I I : I : ; : ; ; 1 o 10 ao 30 40 so eo 70 ao eo loo o 10 ao so ro so so 70 no ao loo %GaitCycle %GaitCycle FR FT* + 30- I I I - - 10-- I I 5 .- + I" -w 10.- 0.- I I c C + .- 0 r" 1 l I I I l i w - Y 2 -10.- I I < Y -10.- I I I -ao- I -ao-- I I - o 3 0 10 7 ao : so : ro II so I : eo : 70 I ao I I eo I loo -307 o I 10 ; ao ; so : I : ro ao ao 70 I eo ; oo , loo %GaitCycle %GaitCycle AS DS* 30- 30- I I I I ao-- I 20.- I - A C C 0 .- 0 .- lo-- + r" w - < -10- -ao-- - a O ? I : I ,I I , ; , , , , , : , o 10 ao so ro so so 70 ao a0 loo o 10 ao so ro so so 70 ao ao loo %GaitCycle %GaitCycle AR DR*Fi ure 5.A J l e motion for subiects with patellofemoral pain (light line, n= 191 and subjects without patellofemoral pain (dark line, n= 191 for all conditionstested. Dotted vertical line delineates the division between stance and swing . phases (62% of the gait cycle). Dashed vertical line indicates terminal -stance. Asterisk (*] indicates the mean ankle dorsiflexion during terminal stance was greater in thebatellofemoral pain group than in the comparisongroup ( P <.05). FR=free walking, FT=fast walking, AS=ascending stairs, DS=descending stairs, ARbascending ramps, DR=descending ramps.Physical Therapy . Volume 77 . Number 10 . October 1997 Powers et al . 107 1
  • 10. 80- so- 8. 0- 8. 0. - - 70-- - 70- C 80- - 8. 0- 0 so-- g .- so-- 30- -107 I o 10 ao no 40 so eo 70 so so loo o 10 ao 30 40 so eo 70 ao eo loo %Gait Cycle %GaitCycle FR FT so- 8. 0- 7. 0- - - 60- 07 o 10 ao ao ro no eo 70 so eo loo o 10 ao ao 40 so eo 70 eo so loo %GaitCycle %GaitCycle AS DS 807 so- 8. 0. 80- - " - 70- 6. 0- - o 7. 0- 80- C O .- 60-- 3- 0 2 4w- a, a, 30-- 5 -107 I o 10 ao 30 ro so eo 70 eo so loo o 10 ao ao ro so eo 70 ao eo loo %GaitCycle %GaitCycle AR DRFigure 6.Knee motion for subjects with patellofemoral pain (light line, n= 191 and subjects without patellofemoral pain (dark line, n= 19) for all conditionstested. Dotted vertical line delineates the division between stance and swing phases (62% of the gait cycle). Dashed vertical line indicates terminalstance. FR=free walking, FT=fast walking, AS=ascending stairs, DS=descending stairs, AR=ascending ramps, DR=descending ramps.1072 . Powers et al Physical Therapy . Volume 77 . Number 10 . October 1997
  • 11. 80 eO1 601- - - 60 40 6 + 30 5 ao p 10 0 -10 -ao o 10 ao 30 40 so so 70 eo eo loo o 10 ao 30 40 60 so 70 80 90 100 % Gaitcycle %GaitCycle FR FT 10- Ot I I o 10 ao 30 40 so eo 70 so eo loo o % Gait Cycle %GaitCycle AS DS 60- - - 8. 0- 40.- C : : : : 1 $ a I lo- 0- . -107 o 10 ao 30 40 so eo 70 so eo loo o 10 ao 30 40 so eo 70 eo eo loo %GaitCycle %Gait Cycle7 AR DRFigure 7.Hip motion for subiects with patellofemoral pain (light line, n= 19) and subiects without patellofemoral pain (dark line, n= 19) for all conditions tested.Dotted vertical line delineates the division between stance and swing .phases (62% of the gait cycle). Dashed vertical line indicates terminal stance. - - .FR=free -walking, FT=fast walking, AS=ascending stairs, DS=descending stairs, AR=ascending ramps, DR=descending rampsPhysical Therapy . Volume 77 . Number 10. October 1997 Powers et al . 1073
  • 12. relationship to the pain that may be present during gait be related to the higher quadriceps femoris muscleis not known at this time and is a limitation that should demand associated with accelerated addressed in f~iturestudies. The lack of an associationbetween quadriceps femoris muscle torque and the FAQ The reduction in gait speed in the PFP group was ascore was not surprising t->ecausemost of the possible function of reduced stride length and cadence, both ofresponses to items in the questionnaire pertained pri- which were less in the PFP group than in the comparisonmarily to pain during functional activities. group in all conditions. The tendency toward decreased terminal swing hip flexion in the PFP group contributedWe did not find a reduction in knee flexion during the to this decreased stride length by limiting the forwardloading response in the PFP group, indicating that these position of the limb at initial contact. As with walkingsubjects [lid not alter the normal knee joint kinematics speed, quadriceps femoris muscle torque was the onlyduring early stance. This finding is contrary to the predictor of stride length in four of the six conditionscollcl~~sions Dillon and colleagues,who reported that of tested. further supporting the relationship betweensubjects with PFP reduce knee flexion during the stance qriadriceps femoris muscle torque and stride variables.phase to minimile the patellofemoral joint reactionforce. Our kinematic data indicate that this gait adapta- Conclusiontion cannot be grneralized to persons with PFP. Our The results of our study have potential clinical implica-findings also suggest that quadriceps femoris muscle tions. Conservative care for individuals with PFP typically .-torque in the PFP group, although reduced, was capable involves both pain management and strengthening ofof providing stability during this phase of the gait cycle. the extensor rnechai~ism.~~~J"he fact that greater iso- metric quadriceps femoris muscle torque was associatedThe primary gait adaptation in the PFP group was a with increased walking speed and stride length suggestsreduction in walking speed, which was consistent across that strength of this muscle group may be an importantall conditions. The greatest differences between groups factor in deterrnini~rgthe gait characteristics of personsoccurred during the more vigorous tasks of fast walking with PFP. Quadriceps femoris muscle strengthening,and ascending ramps, which suggests that the higher- therefore, lnay be useful for improving functional ability,demand activities required greater speed attenuation. a clinical practice already used for persons with PFP.Winter" has demonstrated that a slower gait speed Qiiadriceps femoris muscle strengthening may be par-reducrs the demand of the quadriceps fenloris muscle ticularly important for individuals who want to return toduring initial stance by decreasing the flexion moment. higher-demand activities such as running o r other ath-The reduction of the knee flexion Inornent during letic activities.slower walking is most likely the result of the reducedvertical component of the ground reaction force, which Referencesis the predominant external force contributing to the Thclrofarr, Nl: 1 Perry J. Gail Normol and Pol/~olo~irc~lFunt.lion. Slack Inc; 1992.knee flexion moment. T h r influence of walking speedon the magnitude of the vertical ground reaction force 2 Kadaha hlP. Kamakrislinan HK. Wootrn ME. et al. Repeatability (11has been demonstrated by Powers e t who found a hincm;ltic, kinetic, a n d elcctromyog~.aphicdata ill normal adult p i t .linear relationship between these two variables. There- ,I Orll~opRrc.1989;7:8414-860.fore, a decrease in walking speed could allow for a 3 Hsu A, Perry J , (;ronley JK, Hislop HJ. Q~ladl.iceps force and mvoelectric activity during flexed k n r e stance. Clir~Ortho/). 1993;288:reduction of muscular demand, without a compromise knee kinematics, and is concordant with previousfindings of decreased electroinyographic activity of the 4 Fox TA. Dvsplasia of ttie quadriceps ~liechanism:hvpoplasia of the vastus ~nedialis muscle as related to llle hypernlobile patella syndrome.vastus muscles of subjects with PFP.2n Surg Clin .Vorlh Am. 1975;55:199-226. 5 Dillon PZ, Updyke UF, Allen WC. Gait analvsis w i ~ hI-efcrence toAlthongh it would appear that persons with PFP inay patellae. J Orthop Sporl.s I>hy.s Thpr. 1983;5:127-131. cho~itiromalaciaadopt a slower gait speed as a possible way of reducingthe patellofemoral joint reaction force, there was no 6 Herchuck M, A~ildriacchi Bach RR, Rcider B. Gait adaptations hy TP, paticrits who have a deficient antel-ior crnciate ligament. J Bor~~,Jcrinlrelationship hetuleen the amount of knee pain and S11rg A M . 1990;72:871-877.walking speed for any of the conditions. There was a 7 Fulkrrson ,JP. I-Iuligerford DS. I l i ~ o r d m f the Pnt~llofrrnorol o Joint. 2ndrelationship, however, between quadriceps femoris mris- Mtl: Willhms & UTilkills; 1990. c d . Bal~iniore,cle torque and walking speed for five of the six condi-tions (descending stairs excepted), with increased quad- 8 Halhrecht,1L..Jackso11DW. Acute dislocation OF the patella. In: Fox JM, Dcl Pizzo W, cds. 7hr Polellofumorrrl,/ojnl. Nrw York, NY: MrGraw-riceps femoris muscle torques resulting in faster walking l-lill luc; 1093:123-134.speeds. This association suggests that persons with ,9 (;yo17 AN, C:liac~Em, Staulfer RN. Functional evaluatiori of normalgreater levels of quadriceps femoris muscle torque tend a n d pa~hologicalknees during gait. Arrh P11ysiZf~d Kuliobil. 197&57:571-to demorlstrate greater ainbrllation speeds, which may 577.1074 . Powers et a1 Physical Therapy . Volume 7 7 . Number 1 0 . October 1997
  • 13. 10 Stal~ttcl-KN, C:hao ETi, C;yory AN. Biornechar~iralg a i ~ analysis of 20 Licb KJ, Perry,]. Q~ladricrps Iltnrtion: a n elrrtron~yographic studythe tliseased k n r r ,joint. Clin Orllroj~.1977; 1 2fi:24fi-2i5. under isonretric rontlitions.,] U o n ~ j o i r t SIITXAni. 197l;.i3:749-7.511. t11 Kettlek~mp DB, Lravei-ton PE, Misol S. Ciait rhar;tcteristics of thc 21 Winter DA. Hiorn,rchnnic.r rrnd ~LJolur New (;wn/lol f f H u m n n .Llo7~rrn~nl.rheumatoial knee. A~.rliStrrg. 1972;104:~ZO-34. Kirk, NY John Wiley & Sons Inc; 1990.12 Stratford PW. Electromyography of the qu;tdriccps finloris muscle 22 Maquet PC;. Biome~;/trrni[.r thr Knrt. 2nd ed. Ncw York, NY ujin sut?jects with rlornmal knees iultl acutely effi~sedknees. P11ys 7%rr: Springer-Vrrlag New %I-k lnc; 1984.1981;ti?:27<)-2113. 23 Mathews LS, Sonstrgard DA, Henke JA. Load-braring characteris-13 Stokes M, Young A. Investigations of quadricrps inhihition: impli- tics of the patellofcnloral j o i ~ ~Actcr Orlhop .Sr.nnd. 1977;48:511-516. t.cations for rlinical pl-artice. Plrysiothcrclpy. 1984;70:425-428. 24 Heyvood WB. Rerurrcnt tlisloratiot~ the patella.,] Llonrjoit~l.Surg of14 hlcCor~nell,J. T h e management of chorrcl~~on~alacia patellae: a Rr. 19(il;43:50H-5 17.long-term sl~lution. Austrtllianjo~~rrrnl Il~y,io/hrrcrpy.1986;32:2 1.5-223. of 25 Brossmann J, Muhle C:, Schrotler C. e t al. Patellal- trarking pattcl-ns15 dr.4ndr;rtlc JR, Grant (;, Dixon 4. Joint diste~lsiorl and reflex muscle during active and passibe kner extension: cvaluatior~ with motion-inhibition in the kner. J Ronpjoinl S u ~ g Am. 19fi5;47:313-322. triggered cine MR inlaging. Kndiolo~g.19!)3;1 X7:20.5-212.16 Spencer JI); Hayes KC, ..lexander 1J. I 1 c . r ,joint cffrlsion and 26 Wintel- DA. Kinematic and kinetic patterns in human gait: variabil-q11ac11-ireps I-eflcx inl~ibition man. Arth P1~y.r,/lrd Kr~hfibil.l!lX4;f;.5: in ity a n d roinpensatiug effrcts. Hrtmcirt Mo71ernrlrl Sciunct. 1984;3:51-76.171-1 77. 27 Powers CM, Rao S, Pel-ryJ. Loading charactrristics ill s~~t?jects with17 Young A, Stokes M, Shakrspeal-e DT, Sherman Kt. T h r effect of patellofcmol-al pain. (;nit nrtd IJo.rturr. 1905;3:84. Abstrart.intl-a-artic1.1lar bupivicaine orr quadriceps inhihition after rnerliscec- 28 Powel-s CM. Landel R, Perry J. Tirning ant1 ~ntrnsity v;latus ln~rsclr oftomy. ,Vfr~o Sport.r Exrrr. 1983;1.5:1.54. Abstract. Sri activity during functional activities irr subjerts with aud witho~ltpatcl-18 (:hesworth BM, C u l h a ~ n EG, Tala GE, Peat M. Valiclatio~~ of lofemoral pain. 1hy.r 7 7 1 ~ 19!9fi;76:946-955. ~.outcome measures in patier~ts with patcllofrmoral syndi-ome.,/ Or.thol,S/~mt.r h y 7%rr. 1989; 10:30?-308. P19 Krljala IJM, Jaakkola LH, Koskiner~ SK, et nl. Sroring of pitccl-lofmmral disorders. ,]o~rrr~nl Artl~ro.m~py Rr.lntr(l .Xurqrry. 1993:9: oj find1.59-163. Invited CommentaryI appreciate having the opportunity to comment on this motion in response to PFP. Bioniechanical models alsointeresting and clinically relevant article. Understanding predict increased patellofemoral contact forces, withthe manner in which patients alter their mechanics as a increasing knee flexion and quadriceps femoris muscleresult of either pain or weakness is important for both force.:- Therefore, as noted by Powers e t al, decreasedresearchers and clinicians. Clinicians gain insight into knee flexion during the loading phase of gait activitiespotential problenis that could develop as a result of the appears to be a logical compensatory mechanism forcompensatory pattern and can then integrate preventa- persons with PFP and was the premise of this study.tive strategies into their treatment regimens. Research-ers gain a greater understanding about the mechanisxns The purpose of the investigation was to determine thebehind these altered movement patterns. influence of the quadriceps femoris muscle torqne and PFP on the amount of knee flexion during the loadingI conlrrlend the authors for undertaking a study of this response during a variety of locomotor activities. Thenature, because the manner in which pa~ientscompen- authors hypothesized that pain and weakness would besate for injuries is still not vely well understood. In associated with decreased gait function. What theyaddition, patellofemoral pain (PFP) is enigmatic and found, however, was that neither measure predicted thedifficult to study, presenting an even greater challenge. amount of knee flexion during the loading response ofPatellofemoral joint ~llotion does not lend itself well to the locornotor activities tested. Although the authorsstandard motion analysis techniques, necessitating more offered some explanation for these findings, other fac-invasive p r ~ c e d u r e s . ~ It is a logical assumption, how- . tors might also be considered.ever, that PFP will indirectly lead to abnormalities intibiofeinoral joint motion, which is easier to measure. A critical component of the study of compensatoryThis assumption is supported by the fact that many of us, patterns is the reproduction of the conditions that areas clinicians, have seen patients alter their knee joint hypothesized to lead to the alterations. Among thePhysical Therapy. Volume 77 . Number 10 . October 1997 McClay . 1075