Are patellofemoral pain and qs muscle torque associated with locomotor function

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, ascending 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 associated 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 associated with locomotor function? Phys Ther. 1997;77:1063-1078.1

Key Words: Gait, Patellofemoral pain, Quadriceps femoris muscle torque.

Christopher M Powers I

Jacquelin Pemy

Arthur Hsu

Helen J Hislop

Physical Therapy . Volume 77 . Number 10 . October 1 9 9 7

D uring the stance phase of gait, the knee is believed to be the principal determinant of limb stability.' The quadriceps femoris muscles act as the primary stabilizers of the knee,

especially during loading response, when the knee flexion moment is the g rea te~ t .~ Activity of these muscles is necessary to support the flexed knee posture."

Reduced knee flexion during loading response is gener- ally thought to be an action aimed at limitingjoint forces and may be indicative of knee pathology.' For example, pain and weakness are commonly associated with patellofemoral joint path~logy,~ and the avoidance of knee flexion during stance has been found in persons with patellofemoral joint pathology.~erchuck et a16 used the term "quadriceps avoidance pattern" for persons with anterior cruciate ligament (ACL) deficiency to describe a gait pattern that minimizes the knee flexion moment during the loading response and therefore the demand of the knee extensors. Persons with PFP also may adopt a similar strategy to reduce the patellofemoral joint reaction forces associated with increased knee flexion and quadriceps femoris muscle activity. A quadriceps femoris muscle avoidance pattern could be deleterious to the patient with PFP, however, if further quadriceps femoris muscle atrophy results from disuse. This avoidance pattern may contribute to patellar instability, which is commonly believed to be at least partly the result of weakened dynamic stabilizer^.^.^.^

Although gait patterns have been described for various knee pathologies such as degenerative joint di~ease,' '.~~' rheumatoid arthritis,"-l1 and ACL insufficiency,~ittle is known about subjects with PFP and the relationship between pain and weakness. The relationship between knee pain and quadriceps femoris muscle inhibition, however, has been discussed previously in the literature. Reflex inhibition has been demonstrated in subjects with knee pathology12 and is reported to occur when afferent stimuli from receptors in or around the knee joint result

in inhibition of alpha motoneurons in the anterior horn of the spinal cord.'%lthough in clinical practice pain and inhibition have been associated,14 decreased motor unit recruitment of the quadriceps femoris muscle appears to be linked to knee joint e f f ~ s i o n ~ ~ ~ ' ~ ' " ~ ~ ~ ~ and has been reported to be independent of pain.I2,l" Young et all7 reported that afferent block by local anesthesia was not effective in reducing quadriceps femoris muscle inhibition, despite a complete reduction in pain. Additionally, Stratford12 did not observe a relationship between pain and inhibition that would explain reduced electromyographic activity of the quadriceps femoris muscle during a maximal isometric contraction in persons with acutely effused knees. In con- trast, deAndrade and colleagues15 presented evidence that pain reduction through lidocaine injection reduced quadriceps femoris muscle inhibition in knees that were artificially distended. These observations, however, were made on only four subjects.

Despite the current state of knowledge regarding the cause of quadriceps femoris muscle inhibition, many functionally related questions remain. For example, are compensatory gait patterns a result of pain, weakness, or both? Do gait adaptations associated with patellofemoral joint pathology differ among persons with varying degrees of pain? What is the relationship between PFP and quadriceps femoris muscle weakness? The purpose of our investigation was to determine the influence of PFP and quadriceps femoris muscle weakness on stride characteristics and the amount of knee flexion during the loading response in different gait conditions (level walking, ascending and descending stairs, ascending and descending ramps). Functional assessment scores were also correlated with actual gait characteristics. We hypothesized that there would be a correlation between either pain or quadriceps femoris muscle weakness and the limitations in gait function associated with PFP. This information could assist in identifying variables associated with gait limitations in this population and could

CM Powers, PhD, PT, is Assistant Professor, Department of Biokinesiology and Physical Therapy, University of Southern California, 1.540 E Alcazar St, CHP 135, Los Angeles, CA 90033 (USA) ([email protected]~~). Address all correspondence to Dr Powers.

J Perry, MD, is Chief, Pathokinesiology Service, Rancho Los Amigos Medical Center. Downey, Calif. and Professor, Departrnent of Biokinesiolog and 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.os Angeles.

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 ~ r Physical Therapy IIIC.

Thi~ nrtic.1~ ruas submittpd August 8, 1996, nnd runs occc?t(.cl April 25, 199%

1064 . Powers et al Physical Therapy . Volume 77 . Number 10 . October 1997

Table 1. Subiect Characteristics

with PFP, and they had no other limitations that would alter their gait.

PFPa Group Comparison Group (n = 1 9) (n= 19) P

Age (YI X 25.4 27.5 SD 8.2 4.7 .35 Range 14-46 2 3-3 8

Hcgh t (cm)

X 165.1 165.3 SD 7.6 7.7 .94 Range 151 .l-177.2 149.9-183.5

Weight (kg)

X 62.4 59.2 SD 9.3 7.5 .25 Range 42.0-82.7 46.8-74.1

aitl in guiding treatment programs aimed at improving function.

Method

Subjects Nineteen female sul~jects between the ages of 14 and 46 years with a diagnosis of PFP participated in this study (Tall. 1). Subjects were recruited fi-om the Southern Califorr~ia Orthopaedic Institute (Van Nuys, Calif) and were scl-eened to rule out ligamentous instability, inter- nal der;angement, and patellar tendinitis. In addition, sul~jects did not have any other orthopedic or neurologic impairments, as determined by physical examination and questionnaire, that would adversely affect gait. Each sut!ject':s pain originated from the patellofemoral joint (as determined through their complaints and a physical exatnination), and only patients with histories relating to overuse (ie, symptoms related to repetitive activity) or insidious onset were accepted. The physical examination consisted of passive range of motion, active range of motion, palpation of the patella and related structures, and a patellar grind test. In addition, each subject's pain was readily reproducible with at least two of the following acthities: stair ascent or descent, squatting, kneeling, prolonged sitting, or isometric quadriceps femoris muscle contraction. The subjects with PFP were varied with respect to the severity and duration of symptoms. Sub- jects were excluded from the study if they reported ha~ ing either knee surgery or acute traumatic patellar dislocation.

Nineteen female subjects between the ages of 23 and 38 years served as a comparison group (Tab. 1). These subjects had no history or diagnosis of knee pathology or trauma, and they were free of any current knee pain. In adtlitior~, these subjects did not report discomfort with any of the activities described as criteria for the subjects

Isometric knee extensor torque was recorded using a Lido dyna~~~omete r .* Prior to testing, compensation for limb weight and the effects of gravity was made automat- ically by the dynamometer's computer software program (Version 3.8, 1989). Reliability of the data used for correction was not assessed. Torque data were recorded by a DEC 11/23 computert at a rate of 2,500 Hz. The DEC computer was interfaced with the dynamometer.

Knee pain was recorded using a visual analog pain scale (VAS). The VAS consisted of a 10-cm horizontal line, the ends of which defined the minimum ("no pain") and maximum ("extreme pain") of perceived pain. Each sub ject placed a mark on the line to indicate the intensity of pain. The amount of pain indicated on the line was converted to a numerical value based on the distance (in centimeters) from the minimal possible pain to the mark on the line. The VL4S has been shown by Chesworth et allx to be a valid indicator of pain changes in patients with PFP.

To evaluate symptoins and functional limitations in the subjects with PFP, a functional assessment questionnaire (FAQ developed by Kujala et all'' was used. The validity and reliability of measurelnents obtained with the FAQ have not been reported. This questionnaire contained 13 multiple-choice questions relating to patellofemoral

joint symptoms. Scoring was based on a numerical scale depending on question response, with some items being weighted more than others. The maximum possible score was 100, which represented no pain aild no functional deficits. This scoring system has been demonstrated to differentiate between different classifications of patellofemoral disorders.l0

Stride characteristics were recorded with a micro- processor-based Footswitch Stride Analyzer system.: This system consisted of compression-closing footswitches taped to the soles of the subjects' bare feet. The footswitches contained sensors at the heel, the first and fifth metatarsal heads, and the great toe that responded to compressive loads equal to or greater than 3 psi. Stride characteristics calculated from this system includ- ed: speed, stride length, cadence, single- and double- limb support times, and stance and swing durations.

Sagittal-plane motion of the ankle, knee, and hip joints was measured with a Vicon motion analysis system.s Six

' 1.oredan Biomedical Ill,-, 16.12 Ua \'lnci (:t, PO Box 1154, Davis. (:A 95617. ' Digiral 'quipment C o ~ p , 146 Main St, Maynalrl, MA 01754.

B&1. E:ngincer-~ng, 8807 Pioneel Blvd, Suitr (:. Snt~ta Fc Springs. (1% 90670. ' Oxli~rd Mctrica L.td Unit 14, '7 Weat Way, Botlry. Oxh~ld, Etlgla~ld OX:! OUR.

Physical Therapy . Volume 77 . Number 10 . October 1997 Powers et al . 1065

infrared cameras operating at a 50-HT sampling rate were used.

A 10-m walkway was used for free- and fast-walking trials, with data being collected over the middle 6 m. Analysis of stair use was done with a four-step staircase with a slope of 33.7 degrees, a step height of 20.3 cm, and a tread depth of 30.5 cm. Ramp walking was assessed with a 12-degree incline that was 6.1 nl in length.

Procedure All data collection was performed at the Pathokinesiol- ogy Laboratory, Rancho Los Amigos Medical Center, Downey, Calif. Before testing, all procedures were explained to each subject and informed consent was obtained. Subjects were then asked to complete the FAQ based on their current symptoms and limitations.

Prior to gait analysis, maximal isometric knee extensor torque and knee pain were measured. Subjects were seated on the Lido dynamometer chair with the hips flcxed to 90 degrees and the knee flexed to 60 degrees. The axis of rotation of the dynamometer was then positioned in line with the axis of rotation of the knce, with the resistance arm cuff placed just proximal to the malleoli. A Velcro@ strap1 was placed across the pelvis to enwre proper stabilization. Sixty degrees of knee flexion was used because this position has been found to result in the greatest torque output in female subjects without inlpairment~.'~)

Isometric torque during a 5-second maximal contraction was then recorded. Verbal encol~ragement was given to all sub.jects during the trial. After torque was measured, the subjects with PFP were asked to rate, using the VAS, their knee pain during the maximal contraction. Our rationale for assessing pain during contraction rather than during the locomotor tasks was that we expected that pain scores obtained during ambulation would not reflect true symptoms. We believed that the subjects would most likely adopt gait strategies to reduce or eliminate pain.

Following the torque and pain assessment, subjects were prepared for gait analysis. Footswitches were taped to both of the subjects' bare feet, and the reflective rnarkers that were used to determine sagittal-plane motion were placed at the designated landmarks (posterior heel, fifth metatarsal head, dorsum of the foot, medial and lateral malleoli, anterior tibia, medial and lateral fe~noral epi- condyles, anterior thigh, greater trochanter, bilateral anterior superior iliac spines, and sacrum). One practice trial of both free and fast walking allowed the subjects to beconle familiar with the instrumentation. For free

\ ' r l c ~ - o L'S4 Inc, P C ) Box 5218, 406 BI.OM.II h v r , M d ~ l c h r \ ~ r l - , N11 0::lOX

walking, subjects were instructed to walk at their normal speed. For fast walking, subjects were instructed to walk at a speed as if they were in a hurry. Joint motion and stride characteristics were then assessed simultaneously during free and fast level walking, ascending and descending stairs, and ascending and descending ramps.

Data Analysis Sagittal-joint motion of the ankle, knee, and hip was calculated for all conditions tested. Raw motion data were filtered at 6 HL using a fourth-order, Butterworth recursive filter." The data were then digitized and linearly interpolated to 0.01-second intervals. The stance phase of each stride of motion collected Ivas normalized LO 6'2% of the gait cycle in order to average data from m~~l t ip l e strides and different subjects. We believe this value to be representative of normal walking,[ and it was consistent with the average stance phase deinonstrated by our subjects for all conditions. Maxirnuni and rnini- mum motion for each joint were analyzed for each phase of the gait cycle. Analog signals obtained from the individual footswitch sensors were synchronized with the motion data and were used as event markers to determine the different phases of the gait cycle.

Torque data were integrated at 0.1-second intervals. The torque produced by the limb weight (as determined by the gravity cornpcnsation test) was added to the raw torque to account for the effects of gravity. The greatest value over the 5-second trial was recorded for each subject. To control for the cffkcts of subject size, a11 torque data were normalized by body weight and expressed in newton-meters per kilogram.

The BMDP statistical software' was used for all data analyses. The data were tested for normality of distribu- tion using the Wilks-Shapiro W statistic. All significance levels were set at P<.05.

Subject characteristics (age, height, and weight) were compared between groups using two-sample t tests. Comparison of isometric torque values between groups also was made using a two-sample 1 tcst.

To determine whether w ide charactcristics differed between groups and conditions, a 2 X 6 (group X

condition) two-way analysis of variance (ANOVA) for repeated measures on one variable (condition) was performed. This analysis was repeated for each stride characteristic. Data for stride length and cadence during stair amhulation were omitted from thc analysis due to the limitation imposed on these variables as :i result of the fixed ctair height and depth. Peak motion at each

1066 . Powers et a1 Physical Therapy . Volume 77 . Number 1 0 . October 1997

Table 2. Moximurr Knee Extension Torque (Normalized by Body Weight)

PFPa Group Camparison Group

Tocque (N.m/kg)

0.78 0.69 .03 Range 1.28-3.92 1.96-4.02

" PFP=~x~tc~llofe~~~o~~~il pain.

joint also was compared between groups and conditions using a 2 x 6 (group x condition) two-way ANOVA for repeated measures. This analysis was repeated for each phase of the gait cycle.

To assess the association among PFP, quadriceps femoris muscle torque, and FAQ score, we used the Pearson product-moment correlation coefficient. We used sepa- rate analyses to assess the linear relationship between PFP and torque, PFP and FAQ score, and torque and FAQ score.

Stepwise regression analyses were performed to determine whether any of the independent variables (pain, quadriceps femoris muscle torque, or FAQ score) were predictive of any of the stride characteristics or the alnount of knee flexion during loading response (dependent variables). This analysis was performed for the subjects with PFP only and was repeated for all six walking conditions.

Results

Relationship Among Knee Extensor Torque, Pain, and Functional Assessment Score After normalizing by body weight, the maximum knee extensol- torque of the PFP group was less than that of the cornparison group (2.35 N-m/kg versus 3.04 N.m/kg, Pc .05 ) (Tab. 2) . During the maximal isometric test, the PFP group reported an average pain level of 4.4 out of 10 on the VAS (Tab. 3) . The mean score on the FAQ for the PFP group was 67.5 out of a possible 100 (Tab. 3) .

The VAS pain score was not correlated with knee extensor torque in the PFP group ( r =.03). In addition, knee extensor torque was not correlated with the FAQ score ( r = .25). The VAS pain score, however, demonstrated a correlation with the FAQscore in the PFP group (r=.72, P<.001:1 (Fig. 1).

Stride Characteristics There was a difference between the PFP and comparison groups for walking speed when the data were averaged across all conditions (significant group effect, no interaction) (Fig. 2). Similarly, there was a difference in

Table 3. Individual Volues for Knee Extension Torque, Visuol Analog Poin Scale (VAS), ond Functional Assessment Q~est ionnoire '~ (FAQ) for Subiects With Patellofemorol Pain

Knee Extension VAS (1 0= FAQ ( 1 00= Subject Torque Maximum Maximum No. (Nem/kg) Pain) Function)

1 2.54 8.6 53 2 2.09 7.6 3 5 3 1.45 9.6 3 7 4 3.90 6.5 70 5 1.43 3.4 85 6 2.14 0 73 7 2.74 4.1 84 8 1.78 4.8 73 9 2.2 1 0.2 73

10 1.23 6.8 3 8 11 2.73 0.8 73 12 1.79 1.1 75 13 1.23 3.2 6 2 14 3.16 5.1 6 8 15 2.42 0 100 16 2.21 8.6 45 17 2.92 6.4 8 3 18 3.64 3.8 74 19 3.48 3.0 8 2 -

X 2.35 4.4 67.5 SD 0.78 3.1 18.1

..

Figure 1. Correlation behveen functional assessment questionnaire (FAQ) score and visual analog pain score for subiects with patellofemoral poin (n=19, r =.72, P<.001).

100 8 . . . . . OI

cadeilce and in stride length when the data were averaged across all conditions (except data for ascending and descending stairs, which were omitted from the analysis) (Figs. 3, 4). In general, the PFP group demonstrated decreased values for these stride characteristics cornpared with the other group.

40

The average walking speed of the PFP group (for all conditions) was 81% of the average walking speed of the cornparison group (56.5 m/rnin versus 69.7 m/min,

-- . .


20 I 0 2 4 6 8 10

VISUAL ANALOG PAIN SCORE

FR FT AS DS AR DR

Condition

, Comparison ,-, PFP Group Group

Figure 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 group across all conditions was 88% of the average stride length of the comparison group (1.22 m versus 1.38 m, P<.001) (Fig. 3). Cadence of the PFP group was 91% of that of the comparison group when averaged across all conditions (114.1 steps/min versus 125.2 steps/min, P<.001) (Fig. 4). There were no differences between groups for time spent in single-limb support, double- limb support, swing, and stance.

Of the three variables measured (pain, torque, and FAQ score), knee extensor torque was the only predictor of speed, with higher torque values being associated with higher walking speeds. This association was evident for five of the six conditions (free walking: r=.59, P<.05; fast walking: r =.59, P<.05; ascending stairs: r z.50, P<.05; ascending ramps: r = .62, P<.05; descending ramps: r=.67, P<.05) (Tab. 4). Knee extensor torque also was the only predictor of stride length for four of the six conditions (free walking: r=.73, PC.05; fast walking: r = .61, P<.05; ascending ramps: r = .62, P< .05; descending ramps: r =.76, P<.05) (Tab. 4). No other associations were found between any of the three variables and the remaining stride characteristics.

Joint Motion There was a significant group effect and a significant interaction for ankle joint motion during the terminal stance phase of gait. When conditions were analyzed separately between the two groups, the PFP group demonstrated greater ankle dorsiflexion compared with the other group for fast walking (9.9" versus 7.0". P<.05), descending stairs (27.6" versus 18.g0, P<.001), and descending ramps (15.8" versus 1 l.gO, P<.01) (Fig. 5 ) . No other differences for ankle motion were found. There were no differences in knee motion between groups for any phase of the gait cycle, regardless of the condition (Fig. 6) . Similarly, hip joint motion was not different between groups, regardless of the condition, for any phase of the gait cycle (Fig. 7).

Pain, quadriceps femoris muscle torque, and FAQ score were not predictors of the amount of knee flexion during loading response. This finding was consistent for all conditions tested.

Discussion We found a decrease in knee extensor torque in the PFP group (77% of the knee extension torque of the com-

1068 . Powers et al Physical Therapy. Volume 77 . Number 10 . October 1997

1.8

1.6

1.4

.g 1.2 5 P 1.0 a

$ 0.8 .- L ' 0.6

08.4

0.2

0.0 FR FT AR DR

Condition

Comparison PFP Group Group

Figure 3. Mean stride length for subiects with patellofemoral pain (PFP group, n= 19) and subiects without patellofemoral pain (comparison group, n= 19) for level walk.ing 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 out of a possible 10 during testing. These associated findings suggest that pain may have played a role in reducing quadriceps femoris muscle torque. When pain was correlated with knee extensor torque, however, this inference did not hold true. These two variables appeared to be completely independent of one another (r=.03). This finding would imply that knee extensor torque was not affected by pain, which is consistent with the observations of Stratford" and Young et al."

The lack of an association between knee extensor torque and pain may have been related to numerous factors. For example, patients dealing with persistent pain might tend to protect themselves during an activity in which they would expect to experience pain. Possibly, in order to avoid pain, patients would not produce a maximum torque value that truly reflects their strength. This concept is supported by the fact that 5 of the 19 subjects with PEP reported little or no pain during the maximal isometric quadriceps femoris muscle test. Furthermore, inhibition of quadriceps femoris muscle activity as a result c~f effusion also could have contributed to the reduction in quadriceps femoris muscle torque. Because

we did not assess swelling, we cannot determine whether this really occurred. None of the subjects with PEP, however, demonstrated gross joint effusion.

An alternative explanation for the lack of a correlation between pain and quadriceps femoris muscle torque could be related to the testing position used to elicit knee pain. Our procedure assessed the maximum isometric knee extension torque at 60 degrees of flexion, which placed the quadriceps femoris muscle at its greatest length-tension advantage2" but may have been inad- equate in reproducing the amount of patellar pain that would inhibit normal function. Although the high quadriceps femoris muscle forces produced at this knee flexion angle also would have resulted in substantial patellofemoral joint reaction forces,'"he modest pain scores reported by our subjects suggest that this compression was reasonably tolerated. These relatively low hain scores may have bken the result of the increase in contact surface area between the patella and femur, which has been reported by Mathews and colleagues" to be approximately 40% more at 60 degrees of knee flexion as compared with 15 degrees of flexion. Increased contact area would have reduced the joint


160.0

140.0

h

120.0 c .- < 100.0 V) P a, +

80.0 a, 0 C a, 60.0 3 0

40.0

20.0

0.0 FR FT AR DR

Condition

pFp Group Group

Figure 4. Mean cadence for subjects with patellofemoral pain (PFP group, n= 19) and subiects without patellofemoral pain (comparison group, n= 19) for level walking and ramp walking conditions (stair-climbing data omitted due to the limitations imposed as a result of the fixed stair height and depth). Mean cadence 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.

contact pressure, as the joint forces would have been Table 4- Stepwise Regression Results for Predicting Walking Speed, Stride

distributed over a greater area. In addition, because PFP Length, and Cadence has been linked to patellar s~bluxation*~ and because patellar subluxation has been shown radiographically to occur at angles of less than SO degrees of knee flexion,?" it is possible that testing the subjects with the knee less flexed (ie, 0"-SO0) would have yielded greater pain scores. This position, however, would have placed the quadriceps femoris muscle at a mechanical disadvan- tage" and therefore would have resulted in lower torque values. Given this paradox between testing position and the pain-torque relationship, as well as the need to assess both variables simultaneously for correlation purposes, we believe that it is not surprising that no relationship was found.

Stride Independent Variable Conditiona Characteristic (Predictor) r"

FR Walking speed Knee extension torque .59 FT Walking speed Knee extension torque .59 AS Walking speed Knee extension torque .50 DS Walking speed None AR Walking speed Knee extension torque .62 DR Walking speed Knee extension torque .67 FR Stride length Knee extension torque .73 FT Stride length Knee extension torque .6 1 AR Stride length Knee extension torque .62 AR Stride length Knee extension torque .76 FR Cadence None FT Cadence None AR Cadence None DR Cadence None

An inverse linear association was found between pain and the FAQ score, indicating that the FAQ may be sensitive 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

the FAQ questions related to the reproduction of symp- stairs, AR=ascending ramps, DK=descrnding ramps. Stride lerlgth and cadrnre for ascending and descending staira omitted due to the linritations

toms may explain the correlation between these two the fixed stair and deDth, u

scores. Care must be taken in interpreting these results, "AH r\zalues significant at the P<.05 level. Ellipsis ind~cates not applicable.

however, as we did not assess pain during functional activities. Whether the pain associated with the maximal isometric quadriceps femoris muscle contraction has a

1070 . Powers et a1 Physical Therapy . Volume 77 . Number 10 . October 1997

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 conditions tested. Dotted vertical line delineates the division between stance and swing phases (62% of the gait cycle). Dashed vertical line indicates terminal

30-

- .

stance. Asterisk (*] indicates the mean ankle dorsiflexion during terminal stance was greater in thebatellofemoral pain group than in the comparison group ( P <.05). FR=free walking, FT=fast walking, AS=ascending stairs, DS=descending stairs, ARbascending ramps, DR=descending ramps.

20-

Physical Therapy . Volume 77 . Number 10 . October 1997 Powers et al . 107 1

I -30-

I I -ao--

I - 10- C .-

- a ~ - - a ~ - -

I -30- I .

I 3 0 I I I : I : ; : ; ; 1 o 10 ao 30 40 so eo 7 0 ao eo l o o o 10 ao so r o so so 70 no ao loo

%Gait Cycle %Gait Cycle

FR FT*

I I I

30-

10-- - - 5 10.- .- +

I" 0.- w - Y

2 -10.-

-ao--

I I I I I I C 1 I + c l l i .- 0 I +

I r" I I w -

Y < -10.- I I

-ao- I I

o 10 ao so r o so eo 70 ao eo loo o 10 ao so r o ao ao 70 eo oo loo


AS DS*

I I I I

30-

ao--

A

- 3 0 7 : : I I : : I I I I -307 I ; ; : I : I ; ,

I 30- I I I I 20.- I

- C C 0 .- 0 lo-- .- +

r" w -

-10- < -ao--

I , ; , , - a O ? I : I I , , , , : , o 10 ao so r o so so 70 ao a0 loo o 10 ao so r o so so 70 ao ao loo


AR DR*

Figure 6. Knee motion for subjects with patellofemoral pain (light line, n= 191 and subjects 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 ramps.

80-

1072 . Powers et al Physical Therapy . Volume 77 . Number 10 . October 1997

80.-

70-- -

so-

80..

70- - 80- - 80.- -

C 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


FR FT so-

80.-

70.-

- 60- -

07 o 10 ao ao ro no eo 70 so eo loo o 10 ao ao 40 so eo 70 eo so loo


AS DS 807

80-

70- -

so-

80..

70.- - o 80-

"- 60.-

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


AR DR

Figure 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.

eO1 80

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 %Gait Cycle

FR FT

10-

Ot I I o 10 ao 30 40 so eo 70 so eo loo o

% Gait Cycle %Gait Cycle

AS DS

- . - . FR=free -walking, FT=fast walking, AS=ascending stairs, DS=descending stairs, AR=ascending ramps, DR=descending ramps

60-

80.- - - 40.- C

$ I a lo- 0.-

-107

Physical 'Therapy . Volume 77 . Number 10. October 1997 Powers et al . 1073

1::::

o 10 ao 30 40 so eo 70 so eo loo o 10 ao 30 40 so eo 70 eo eo loo


AR DR 7

relationship to the pain that may be present during gait is not known at this time and is a limitation that should be addressed in f~iture studies. The lack of an association between quadriceps femoris muscle torque and the FAQ score was not surprising t->ecause most of the possible responses to items in the questionnaire pertained pri- marily to pain during functional activities.

We did not find a reduction in knee flexion during the loading response in the PFP group, indicating that these subjects [lid not alter the normal knee joint kinematics during early stance. This finding is contrary to the collcl~~sions of Dillon and colleagues,who reported that subjects with PFP reduce knee flexion during the stance phase to minimile the patellofemoral joint reaction force. Our kinematic data indicate that this gait adaptation cannot be grneralized to persons with PFP. Our findings also suggest that quadriceps femoris muscle torque in the PFP group, although reduced, was capable of providing stability during this phase of the gait cycle.

The primary gait adaptation in the PFP group was a reduction in walking speed, which was consistent across all conditions. The greatest differences between groups occurred during the more vigorous tasks of fast walking and ascending ramps, which suggests that the higher- demand activities required greater speed attenuation. Winter"' has demonstrated that a slower gait speed reducrs the demand of the quadriceps fenloris muscle during initial stance by decreasing the flexion moment. The reduction of the knee flexion Inornent during slower walking is most likely the result of the reduced vertical component of the ground reaction force, which is the predominant external force contributing to the knee flexion moment. Thr influence of walking speed on the magnitude of the vertical ground reaction force has been demonstrated by Powers et who found a linear relationship between these two variables. There- fore, a decrease in walking speed could allow for a reduction of muscular demand, without a compromise in knee kinematics, and is concordant with previous findings of decreased electroinyographic activity of the vastus muscles of subjects with PFP.2n

Althongh it would appear that persons with PFP inay adopt a slower gait speed as a possible way of reducing the patellofemoral joint reaction force, there was no relationship hetuleen the amount of knee pain and walking speed for any of the conditions. There was a relationship, however, between quadriceps femoris mris- cle torque and walking speed for five of the six conditions (descending stairs excepted), with increased quadriceps femoris muscle torques resulting in faster walking speeds. This association suggests that persons with greater levels of quadriceps femoris muscle torque tend to demorlstrate greater ainbrllation speeds, which may

be related to the higher quadriceps femoris muscle demand associated with accelerated speed.

The reduction in gait speed in the PFP group was a function of reduced stride length and cadence, both of which were less in the PFP group than in the comparison group in all conditions. The tendency toward decreased terminal swing hip flexion in the PFP group contributed to this decreased stride length by limiting the forward position of the limb at initial contact. As with walking speed, quadriceps femoris muscle torque was the only predictor of stride length in four of the six conditions tested. further supporting the relationship between qriadriceps femoris muscle torque and stride variables.

Conclusion The results of our study have potential clinical implica- tions. Conservative care for individuals with PFP typically . - involves both pain management and strengthening of the extensor rnechai~ism.~~~J"he fact that greater isometric quadriceps femoris muscle torque was associated with increased walking speed and stride length suggests that strength of this muscle group may be an important factor in deterrnini~rg the gait characteristics of persons with PFP. Quadriceps femoris muscle strengthening, therefore, lnay be useful for improving functional ability, a clinical practice already used for persons with PFP. Qiiadriceps femoris muscle strengthening may be par- ticularly important for individuals who want to return to higher-demand activities such as running or other ath- letic activities.

References 1 Perry J. Gail Anoly.ci.5: Normol and Pol/~olo~irc~lFunt.lion. Thclrofarr, Nl: Slack Inc; 1992.

2 Kadaha hlP. Kamakrislinan HK. Wootrn ME. et al. Repeatability (11' hincm;ltic, kinetic, and elcctromyog~.aphic data ill normal adult p i t .

,I Orll~op Rrc. 1989;7:8414-860.

3 Hsu A, Perry J , (;ronley JK, Hislop HJ. Q~ladl.iceps force and mvoelectric activity during flexed knre stance. Clir~ Ortho/). 1993;288: 254-262.

4 Fox TA. Dvsplasia of ttie quadriceps ~liechanism: hvpoplasia of the vastus ~nedialis muscle as related to llle hypernlobile patella syndrome. Surg Clin .Vorlh Am. 1975;55:199-226.

5 Dillon PZ, Updyke U'F, Allen WC. Gait analvsis w i ~ h I-efcrence t o

cho~itiromalacia patellae. J Orthop Sporl.s I>hy.s Thpr. 1983;5: 127-131.

6 Herchuck M, A~ildriacchi TP, Bach RR, Rcider B. Gait adaptations hy paticrits who have a deficient antel-ior crnciate ligament. J Bor~~,Jcrinl S11rg AM. 1990;72:871-877.

7 Fulkrrson ,JP. I-Iuligerford DS. I l i ~ o r d m of the Pnt~llofrrnorol Joint. 2nd cd . Bal~iniore, Mtl: Willhms & UTilkills; 1990.

8 Halhrecht,1L..Jackso11 DW. Acute dislocation OF the patella. In: Fox JM, Dcl Pizzo W, cds. 7'hr Polellofumorrrl,/ojnl. Nrw York, NY: MrGraw- l-lill luc; 1093:123-134.

,9 (;yo17 AN, C:liac~ Em, Staulfer RN. Functional evaluatiori of normal and pa~hological knees during gait. Arrh P11ys iZf~d Kuliobil. 197&57:571- 577.

1074 . Powers et a1 Physical Therapy . Volume 7 7 . Number 10 . October 1997

10 Stal~ttcl- KN, C:hao ETi, C;yory AN. Biornechar~iral g a i ~ analysis of the tliseased knr r ,joint. Clin Orllroj~. 1977; 1 2fi:24fi-2i5.

11 Kett lek~mp DB, Lravei-ton PE, Misol S. Ciait rhar;tcteristics of thc rheumatoial knee. A~.rli Strrg. 1972;104:~ZO-34.

12 Stratford PW. Electromyography of the qu;tdriccps finloris muscle\ in sut?jects with rlornmal knees iultl acutely effi~sed knees. P11ys 7%rr: 1981 ;ti?:27<)-2113.

13 Stokes M, Young A. Investigations of quadricrps inhihition: impli- cations for rlinical pl-artice. Plrysiothcrclpy. 1984;70:425-428.

14 hlcCor~nell ,J. The management of chorrcl~~on~alacia patellae: a long-term sl~lution. Austrtllianjo~~rrrnl of I'l~y,\io/hrrcrpy. 1986;32:2 1.5-223.

15 dr.4ndr;rtlc JR, Grant (;, Dixon '4. Joint diste~lsiorl and reflex muscle inhibition in the kner. J Ronpjoinl S u ~ g Am. 19fi5;47:313-322.

16 Spencer J I ) ; Hayes KC, ..\lexander 1J. I 1 c . r ,joint cffrlsion and q11ac11-ireps I-eflcx inl~ibition in man. Arth P1~y.r ,\/lrd Kr~hfibil. l!lX4;f;.5: 171-1 77.

17 Young A, Stokes M, Shakrspeal-e DT, Sherman Kt'. T h r effect of intl-a-artic1.1lar bupivicaine orr quadriceps inhihition after rnerliscec- tomy. ,Vfr~o' Sri Sport.r Exrrr. 1983;1.5: 1.54. Abstract.

18 (:hesworth BM, Culha~n EG, Tala GE, Peat M. Valiclatio~~ of outcome measures in patier~ts with patcllofrmoral syndi-ome. ,/ Or.thol, S/~mt.r P h y 7%rr. 1989; 10:30?-308.

19 Krljala IJM, Jaakkola LH, Koskiner~ SK, et nl. Sroring of pitccl- lofmmral disorders. , ]o~rrr~nl oj' Artl~ro.m~py find Rr.lntr(l .Xurqrry. 1993:9: 1.59-163.

Invited Commentary I appreciate having the opportunity to comment on this interesting and clinically relevant article. Understanding the manner in which patients alter their mechanics as a result of either pain or weakness is important for both researchers and clinicians. Clinicians gain insight into potential problenis that could develop as a result of the compensatory pattern and can then integrate preventa- tive strategies into their treatment regimens. Research- ers gain a greater understanding about the mechanisxns behind these altered movement patterns.

I conlrrlend the authors for undertaking a study of this nature, because the manner in which pa~ients compen- sate for injuries is still not vely well understood. In addition, patellofemoral pain (PFP) is enigmatic and difficult to study, presenting an even greater challenge. Patellofemoral joint ~llotion does not lend itself well to standard motion analysis techniques, necessitating more invasive pr~cedures.~. ' It is a logical assumption, however, that PFP will indirectly lead to abnormalities in tibiofeinoral joint motion, which is easier to measure. This assumption is supported by the fact that many of us, as clinicians, have seen patients alter their knee joint

20 Licb KJ , Perry,]. Q~ladricrps Iltnrtion: an elrrtron~yographic study under isonretric rontlitions.,] U o n ~ j o i r t t SIITX Ani. 197l;.i3:749-7.511.

21 Winter DA. Hiorn,rchnnic.r rrnd ~LJolur (;wn/lol f f H u m n n .Llo7~rrn~nl. New Kirk, NY John Wiley & Sons Inc; 1990.

22 Maquet PC;. Biome~;/trrni[.r uj' thr Knrt. 2nd ed. Ncw York, NY Springer-Vrrlag New %I-k lnc; 1984.

23 Mathews LS, Sonstrgard DA, Henke JA. Load-braring characteristics of the patellofcnloral j o i ~ ~ t . Actcr Orlhop .Sr.nnd. 1977;48:511-516.

24 Heyvood WB. Rerurrcnt tlisloratiot~ of the patella.,] Llonrjoit~l .Surg Rr. 19(il;43:50H-5 17.

25 Brossmann J, Muhle C:, Schrotler C. e t al. Patellal- trarking pattcl-ns during active and passibe kner extension: cvaluatior~ with motion- triggered cine MR inlaging. Kndiolo~g. 19!)3;1 X7:20.5-212.

26 Wintel- DA. Kinematic and kinetic patterns in human gait: variabil- ity and roinpensatiug effrcts. Hrtmcirt Mo71ernrlrl Sciunct. 1984;3:51-76.

27 Powers CM, Rao S, Pel-ry J. Loading charactrristics ill s~~t?jects with patellofcmol-al pain. (;nit nrtd IJo.rturr. 1905;3:84. Abstrart.

28 Powel-s CM. Landel R, Perry J. Tirning ant1 ~ntrnsi ty of v;latus ln~rsclr activity during functional activities i r r subjerts with aud witho~lt patcl- lofemoral pain. 1'hy.r 7 7 1 ~ ~ . 19!9fi;76:946-955.

motion in response to PFP. Bioniechanical models also predict increased patellofemoral contact forces, with increasing knee flexion and quadriceps femoris muscle force.':-' Therefore, as noted by Powers et al, decreased knee flexion during the loading phase of gait activities appears to be a logical compensatory mechanism for persons with PFP and was the premise of this study.

The purpose of the investigation was to determine the influence of the quadriceps femoris muscle torqne and PFP on the amount of knee flexion during the loading response during a variety of locomotor activities. The authors hypothesized that pain and weakness would be associated with decreased gait function. What they found, however, was that neither measure predicted the amount of knee flexion during the loading response of the locornotor activities tested. Although the authors offered some explanation for these findings, other factors might also be considered.

A critical component of the study of compensatory patterns is the reproduction of the conditions that are hypothesized to lead to the alterations. Among the

Physical Therapy. Volume 77 . Number 10 . October 1997 McClay . 1075

Are patellofemoral pain and qs muscle torque associated with locomotor function

Education

Transcript of Are patellofemoral pain and qs muscle torque associated with locomotor function