Comparison of vastus medialis 0bliquus vastus lateralis muscle integrated electromyographic

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Comparison of vastus medialis 0bliquus vastus lateralis muscle integrated electromyographic

  1. 1. Research ReportComparison of Vastus Medialis 0bliquus:Vastus~aterdis Muscle Integrated Electromyographic RatiosBetween Healthy Subjects and Patients withPatellofemoral Pain fie purpose of this study was to compare vastus medialis obliquus:vastuslateralis Daniel R Souza muscle (VM0:VL)integrated electromyographic (IEMG) ratios of healthy subjects Michael T Gross and patients with unilateral patellofemoral pain (PFP) under isotonic and isomet- ric quadricepsfemoris muscle contraction conditions. Subjects ranging in agefrom 18 to 35 years @=28.06, SD=5.97) were assigned to one of three groups on the basis of type of knee condition. In group I, which consisted of seven healthy control subjects with no history of knee pathology, both knees were tested.In group 2, which consisted of nine patients with unilateral PFP, only the painful knee was tested. In group 3, which consisted of the same nine patients who com-prised group 2, only the nonpainful knee was tested Nonnormalized and nor- malized VM0:VLIEMG ratios were computed for ascending stairs, descending stairs, submaximal isometric contraction, and maximal isometric contraction (nonnormulized only). A two-way analysis of variance for repeated measures in- dicated VM0:VLratiosfor isotonic stair-climbing activities were signiJicantlygreater than VM0:VLratiosfor isometric contractions.Nonnormulized VM0:VL ratios in group I were sgniJicant&greater than nonnormalized VM0:VLratios in the other two groups. Patients with PFP may have abnormal VM0:VLactivationpattern, and isotonic quadncepsfemoris muscle exercise may elicit more favor- able muscle activation patterns than isometric exercbe for patients with PFP. [Souza DR, G r m M7: Comparison of vastus medialis ob1iquus:vastuslateralis muscle integrated electromyographic ratios between healthy subjects and patients with patellofeemoral pain. Phys Ther. 1991;71:310-320.1Key Words: E1ectrom~)ography; Exercise, general; Lower extremity, knee; Muscleperfomzance, measurement;Pain. Disturbances of the patellofemoral mechanism have been identified as one of the most commonly encoun-D Souza, MS, PT, is in private practice at Sanger Orthopedic and Sports Physical Therapy, 2570 Jen-sen St, #108, Sanger. CA 93657. He was a graduate student, Division of Physical Therapy, The Uni- tered abnormalities involving theversity of North Carolina at Chapel Hill, when this study was conducted. This study was completed knee joint. Abnormal lateral trackingin partial fulfillment of the requirements for Mr Souzas masters degree, Department of Medical of the patella is one suggested causeAllied Health Professions, School of Medicine, The University of North Carolina at Chapel Hill. of patellofemoral pain (PFP). Abnor-M Gross, PhD, PT, is Assistant Professor, Division of Physical Therapy, The University of North mal lateral tracking o the patella may fCarolina at Chapel Hill, CB #7135 Medical School Wing E 222H, Chapel Hill, NC 27599-7135(USA). Address all correspondence to Dr Gross. elevate patellofemoral contact pres- sures and precipitate pathology inThis project was approved by the Committee on the Protection of the Rights of Human Subjects at patellofemoral articular cartilage.24The University of North Carolina at Chapel Hill. Proposed mechanisms for abnormalThis article was submitted July 28, 1989, and was accepted November 20, 1990. lateral patellar tracking are abnormali-58/310 Physical Therapy /Volume 71, Number 4 /April 1991
  2. 2. ties in the static soft-tissue restraints The previously described exercise years, X=29.14, SD=5.98) with noof the patella, such as the retinacula5; protocols are also based on the as- history of knee pathology, both kneesvariability in the bony congruency sumption that specific exercises that were tested. Subjects in this groupbetween the patellar and femoral ar- elicit relatively larger VM0:VL EMG were recruited from the faculty andticular surfaces6; and increased Q an- ratios can effect a change in the activa- student population of The Universitygle, or increased angulation between tion patterns of the quadriceps femo- of North Carolina at Chapel Hill. Inthe femoral longitudinal axis and the ris muscle components during the group 2, which consisted of 9 patientsorientation of the patellar ligament.5 performance of functional activities. with unilateral PFP (1 man, 8 women;One other suggested mechanism for We were unable to identify studies age range= 18-35 years; X=27.22,abnormal lateral tracking of the pa- that have documented whether SD=6.18), only the affected (ie, pain-tella is an imbalance in the activity of VM0:VL EMG ratios elicited by iso- ful) knee was tested. Subjects in thisthe vastus medialis obliquus muscle tonic muscle contractions during group either were being treated for(VMO) relative to the vastus lateralis functional movements differ from PFP by medical personnel at the Stu-muscle (VL.). Several investigators VM0:VL ratios elicited by isometric dent Health Service at the universityhave examined the electromyographic contractions. DarlingH has docu- or were recruited from the commu-(EMG) activity of the vastus medialis mented that VM0:VL integrated elec- nity. All group 2 subjects complainedmuscle (or the VMO) and the VL or tromyographic (IEMG) ratios do not of pain that they localized to the ante-have constructed VM0:VL ratios to differ among isometric and non- rior aspect of the knee. In group 3,assess imbalances for various groups weight-bearing isotonic muscle con- which consisted of the same subjectsof individuals or for various types of tractions or among non-weight- who comprised group 2, only the un-muscle contractions. Mariani and bearing muscle contractions affected (ie, nonpainful) knee wasCarus07 reported that, during terminal performed on an isokinetic exercise tested. Each subject signed a state-knee extension, subjects with sublux- device. Blanpied12 has suggested dif- ment of informed consent prior toating patellae had decreased vastus ferences in VM0:VL IEMG ratios participating in the study.medialis muscle EMG activity com- among non-weight-bearing concen-pared with VL EMG activity. Healthy tric, non-weight-bearing eccentric, The investigators excluded fromsubjects in the study by Mariani and and isometric exercises. The statistical group 2 potential subjects who re-Caruso had equal EMG levels for both significance of these differences, how- ported (1) pain on palpation of themuscles (luring terminal knee exten- ever, was not evaluated by appropri- quadriceps tendon or the patellar lig-sion. Other investigators8a9 have ex- ate post hoc testing. ament, (2) a snapping sensation at theamined VMO and VL EMG levels in knee or reported tenderness on pal-patients with PFP, but have not used The purpose of this study was to test pation medial to the patella suggestivecontrol groups. Investigations that the null hypothesis that VM0:VL IEMG of plica,l3 or (3) pain on palpation oflack control groups are not able to ratios (1) would not differ between the knee joint line or with applicationprovide documented differences in healthy subjects and patients with uni- of the McMurrays test for meniscalthe activity of components of the lateral PFP, (2) would not differ involvement.* Subjects in group 2quadriceps femoris muscle in indi- among several isotonic and isometric reported they had not experiencedviduals with PFP and in individuals quadriceps femoris muscle contrac- any trauma or surgical procedures towho do riot have patellofemoral tion conditions, and (3) would not be the affected knee during the 2 yearspathology. affected by an interaction between prior to testing. Group 2 subjects also type of knee condition and type of had no joint ehsion of the affectedTreatment protocols for patients with muscle contraction. knee at the time of testing.Joint efu-PFP often incorporate exercises to sion was defined operationally asstrengthen the VMO selectively.l23>l0 Method midpatellar knee girth of the affectedExercises designed to effect changes knee being greater than 105% of thein the activity of components of the Subjects girth of the unaffected knee.15quadriceps femoris muscle are basedon the existence of differences in acti- Subjects for this study were 6 men Instrumentationvation patterns between healthy indi- and 10 women ranging in age fromviduals and individuals with PFP. 18 to 35 years @=28.06, SD=5.97). The EMG data were acquired usingOnly the study by Mariani and The subjects were assigned to one of the Therapeutics Unlimited GCS-67Carus07 supports the claim that pa- three groups on the basis of type of multichannel EMG system.*This sys-tients with PFP differ from healthy knee condition. In group 1, which tem uses two 8-mm-diameter silver-individuals concerning VMO and VL consisted of 7 healthy control subjects silver chloride electrodes with an on-activation patterns. (5 men, 2 women; age range=21-36 site solid-state amplifier embedded in a plastic enclosure. The interelectrode distance is 22 mm between each member of the electrode pair. TheTherapeutics Unlimited Inc, 2835 Friendship St, Iowa City, IA 52240. preamplified signals are transmittedPhysical Therapy /Volume 71, Number 4 /April 1991
  3. 3. by "hard wiring" and amplified again. in maintaining a standard stepping quadriceps femoris muscle contrac-Total gain settings available range be- rate (92 steps/min) for ascending and tions performed at terminal knee ex-tween 500 and 10,000.The frequency descending the stairs. tension.4JWe used a universal goni-response of the system is 40 to 4,000 ometer to determine knee positionHz, the common mode rejection ratio Procedure for the first muscle contraction andis 87 dB at 60 Hz, and the input im- then relied on the goniometric dialpedance is greater than 15 MR at 100 The midpatellar girth of the tested on the CybexmI1 dynamometer toHz. The raw EMG signals were re- knee was measured for each subject maintain consistent knee joint posi-corded on a Vetter Model E F tape M in groups 2 and 3. Girth measure- tioning for subsequent musclerecorder.+A Tektronix 5111A/R511A ments were performed with each sub- contractions.storage oscilloscopes was used to ject in the supine position. We didmonitor EMG signals qualitatively not assess the reliability of the girth Each subject performed several SICSand to provide each subject with measurements. Individuals who did to become familiar with the testingvisual feedback regarding torque not meet the previously described apparatus and then performed threeproduction for submaximal isomet- criteria for joint effusion were ex- MICs. Each subject maintained eachric contractions. cluded from the study. MIC for approximately 5 seconds and rested for 2 minutes between contrac-The EMG data were acquired from We prepared each subject for EMG tions. Peak torque production duringthe F recorder at 1,000 Hz using a M electrode placement by shaving the these contractions was recorded onTecmar Labmaster analog-to-digital skin of each electrode site with a the storage oscilloscope. Electromyo-converters and were processed using safety razor and then wiping the site graphic data were not acquired dur-an IBM PCBT computed1and a cus- with isopropyl alcohol. Double-sided ing these muscle contractions. Thesetomized software program written adhesive tape and conducting gel trials were used only to identify ausing ASYST programming software.# were applied to each electrode. A torque level for each subject that wasThe DC offset was removed from the longitudinal electrode placement, as 25% of maximal torque productionraw EMG data acquired from each described by Basmajian and Blumen- (ie, 25% relative to the largest torquemuscle. The data were then processed stein,16was used for the VL. The VMO from the three trials). We did not as-using full-wave rectification, followed electrode was placed over the distal sess the reliability of the torque mea-by mathematical integration. portion of the vastus medialis mus- surements. The investigators placed cle" and was oriented transversely to an oscilloscope channel marker at aA Cybefl I1 isokinetic dynamometers* the muscle fibers because of the short position corresponding to 25% of thewas used to measure maximal and course of the muscle. largest torque produced during thesubmaximal isometric knee extension three MICs.torque. Stairs consisting of three steps The order of testing right and leftwere used to elicit concentric and lower extremities was determined Each subject then performed threeeccentric isotonic quadriceps femoris randomly for each subject. We posi- SICS at this 25% level using the oscil-muscle contractions. Each step was tioned each subject for submaximal loscope feedback to maintain a con-25.4 cm (10 in) high and 20.3 cm (8 and maximal isometric quadriceps sistent torque level. Subjects main-in) deep. Switches powered by 1.5-V femoris muscle contractions (SICS and tained each SIC for 5 seconds andbatteries were secured to the left and MICs, respectively) of the first test leg. rested for 1 minute between contrac-right sides of the middle step to pro- Each subject sat in the CybexB I1 test tions. Electromyographic and torquevide signals that would indicate the chair with hips flexed at approxi- data were recorded on F tape for Mbeginning and end of foot contact for mately 80 degrees and the tested the three contractions. Computer soft-each lower extremity. Electromyo- knee flexed at 10 degrees. We se- ware was used as previously de-graphic signals and voltage signals lected 10 degrees of knee flexion for scribed to determine the IEMGfrom each switch were recorded si- the test position based on research value for the middle 3 seconds ofmultaneously on FM tape. A metro- that indicates patellofemoral contact each SIC. The principal investigatornome was used to assist each subject pressure decreases for isometric (DRS) then calculated the average IEMG value across the three SIC trials for each muscle. The average IEMG value for each muscle was+AR Vetter Co, PO Box 143, Rebersburg, PA 16872. used for data analysis.*Tektronix Inc, Howard Vollum Industrial Park, PO Box 500, Beavcrton, OR 97077. Each subject then performed three~echrnarInc, Personal Computer Products Div, 6225 Cochran Rd; Solon, OH 44139 MICs, maintaining each muscle con-l11ntcrnationalBusiness Machines Corp, PO Box 13284, Boca Raton, FL 33432. traction for 5 seconds and resting for 2 minutes between contractions. Elec- Software, 866 3rd Ave, New York, NY 10022.#~ac~illan tromyographic and torque data were**Cybex,Div of Lurnex Inc, 2100 Smithtown Ave, Ronkonkoma, NY 11779. recorded on F tape for the three M Physical Therapy /Volume 71, Number 4 /April 1991
  4. 4. MIC trials. The average IEMG valuewas calculated for each muscle for theMIC trials in the same manner de-scribed for the SIC trials. We repeatedthe MIC and SIC data-collection pro-cedure for each subjects oppositelower extremity after data collection - . Table 1 Normalized Vastus Medialis 0bliquus:VastusLateralis Muscle (VMOVL) Integrated Electromyographic (IEMG) Ratios for Groups, Muscle Contraction Conditions, and Group x Condition Interactionf Groupb Condltloncfor the MIC and SIC trials had been 1 2 3 Meanscompleted for the first test leg. CON 1.1820.22 1.26e0.26 1.4320.24 1.2720.25Following isometric testing, we col-lected data for concentric and eccen- ECC 1.1520.36 1.1320.30 1.2520.27 1.17c0.31tric quadriceps femoris muscle con- SIC 0.9620.17 0.95r0.10 1.1320.14 l.OOrt0.16tractions (CONs and ECCs, Group means 1.10e0.27 13020.25 1.10rt0.26respectively) performed by the sub-jects during ascent and descent of the "Data are meanskstandard deviations for IEMG ratios formed by dividing normalized VMO IEMGstairs. The order of right- and left-leg value by normalized vastus medialis muscle IEMG value.testing was the same as the order hGroup l=healthy control subjects (both knees); group 2=patients with patellofemoral pain (af-used for the isometric testing condi- fected knees); group 3=patients with patellofemoral pain (unaffected knees).tions. Subjects had approximately 10 CON=concentric quadriceps femoris muscle contraction elicited during ascent of steps;minutes of rest berween isometric ECC=eccentric quadriceps femoris muscle contraction elicited during descent of steps;and isotonic testing conditions. Each SIC=submaximal isometric quadriceps femoris muscle contraction.subject ascended the stairs and per-formed the CON by making contact Data Analysis HSD analysis indicated that thewith each successive step first with VM0:VL IEMG ratios for the CON andthe test leg and then with the oppo- The IEMG value for each muscle was the ECC conditions were significantlysite leg. We elicited an ECC from each normalized for the CON, ECC, and greater than the VM0:VL IEMG ratiossubject by having the subject descend SIC conditions by dividing the IEMG for the SIC condition (HSD=.147,from each step in a nonreciprocal value for each condition by the mus- df=58, P<.Ol).fashion. Elach subject descended the cles IEMG value for the MIC condi-stairs and performed the ECC by mak- tion. The purpose of data normaliza- Discussioning contact with each successive step tion was to allow comparison amongfirst with the opposite leg and then the three groups.9 The dependent The results for the normalizedwith the test leg. variable assessed was the normalized VM0:VL IEMG data indicate no differ- VM0:VL ratio. The two independent ences in VM0:VL IEMG ratios acrossPrior to data collection, each subject variables were type of knee condition the three groups and suggest that pa-practiced ascending and descending and muscle contraction condition. An tients with PFP may not differ fromthe stairs several times using the met- ANOVA was conducted with repeated healthy individuals with regard toronome to maintain a stepping fre- measures on one factor: muscle con- VM0:VL activation patterns. Followingquency of 92 steps/min. We recorded traction condition. The alpha level for the initial data analysis, however, weEMG and footswitch data on F tape M the ANOVA procedure was .05. A realized a potential threat to compari-for three CONS and three ECCs for Tukeys Honestly Significant Differ- son among the three groups for theeach leg. Integrated electromyo- ence (HSD) Test was used to perform analysis of the normalized data. Thisgraphic values were calculated for the post hoc contrasts. potential threat to validity involves anCONS beginning with foot contact of effect of type of knee condition onthe test leg and ending with foot con- Results the normalizing MIC. Each normal-tact of the opposite leg during ascent ized VM0:VL IEMG ratio is expressedof the stairs. The IEMG values for the Mean VM0:VL IEMG ratios for the as a percentage of the VM0:VL IEMGthree CONS were averaged and used analysis of normalized data are pre- value for the normalizing MIC. If sub-for data analysis. The average duration sented in Table 1 and Figure 1, and jects within a group had the sameof the thn:e CONs also was calculated the ANOVA results are shown in abnormal VM0:VL IEMG ratios for thefor each muscle. Integrated electro- Table 2. The interaction between type normalizing contraction and the othermyographic values were calculated for of knee condition and muscle con- three muscle contraction conditions,the ECCs beginning with foot contact traction condition was not statistically potential differences among the threeof the opposite leg and extending for significant, and no differences were groups could have gone undetected.the average duration of the three identified across the three groups. A second analysis was conducted,CONS.The IEMG values for the three Significant differences were identified, therefore, using nonnormalized IEMGECCs were averaged and used for however, across the three muscle data from the four muscle contractiondata analysis. contraction conditions. The Tukey conditions (SIC, MIC, CON, and ECC).Physical Therapy /Volume 71, Number 4 /April 1991 313/61
  5. 5. condition and muscle contraction condition did not interact significantly to affect the VM0:VL IEMG ratios. Sig- nificant differences were present across the three groups. The Tukey HSD analysis (HSD=.157, df=29, P<.01) indicated that the VM0:VL IEMG ratios for group 1 were signifi- cantly greater than the ratios for groups 2 and 3. Significant differences also were present across the four muscle contraction conditions. The Tukey HSD analysis indicated that the VM0:VL IEMG ratios for the ECC (HSD=.048, df=87, P<.05) and CON (HSD=.059, df=87, P<.01) conditions were significantly greater than the VM0:VL IEMG ratios for the SIC and MIC conditions. An interesting aspect of the results for the two analyses pertains to the effect of type of knee condition on VM0:VL CON ECC SIC IEMG ratios. Significant differences were detected across the three groups CONDITION for the analysis of nonnormalized data, but not for the analysis of nor-Figure 1. Normalized vastus medialis 06liquus:vastus lateralis muscle (VM0:VL) malized data. Differences in theintegrated electromyographic (IEMG) ratios O=Group I , healthy control subjects (bothknees); O=group 2, patients with patellofemoral pain (affected knees); O=group 3, pa- VM0:VL ratios among the groups fortients with patellofemoral pain (unaffected knees). CON=concentric isotonic quadnceps the normalizing contraction may havefemoris muscle contraction performed during the ascent of a step; ECC=eccentric iso- resulted in the inability to detect dif- tonic quadriceps femoris muscle contraction performed during the descent of a step; ferences among the three groups forSIC=submauirnal isometric quadriceps femoris muscle contraction. the analysis of the normalized- VM0:VL ratios for the SIC, CON, andConclusions based on this analysis of Mean VM0:VL IEMG ratios for the ECC conditions.nonnormalized data are independent analysis of nonnormalized data areof the assumption of no effect of type presented in Table 3 and Figure 2, The major threat to the validity of de-of knee condition on a normalizing and the ANOVA results are shown in tecting dserences across groups incontraction. Table 4. The variables type of knee the analysis of nonnormalized data is the effect of electrode placement on IEMG values. We did not conduct a reliability analysis to assess the signifi-Table 2. Analysis-of-Variance Results for Effects of Group and Condition o n cance of this threat to the validity o fNormalized Vastus Medialis 06liquus:Vastus Lateralis Muscle Integrated nonnormalized measurements. TheElectromyographic Ratios nonnormalized results for between- groups comparisons, therefore, should be interpreted with cautionSource df SS MS F until the reliability is established for the analysis of nonnormalized dataBetween subjects acquired with the method described Group 2 0.55 0.27 2.71 in this article. Error 29 2.94 0.10 Exercising the previously noted cau-Within subjects tion, the significant differences across Condition 2 1.13 0.56 14.96= groups revealed by analysis of the Condition x group 4 0.08 0.02 0.51 nonnormalized data suggest that indi- Error 58 2.19 0.04 viduals with PFP may differ from healthy individuals with regard to quadriceps femoris muscle activation62 /314 Physical Therapy /Volume 71, Number 4 /April 1991
  6. 6. -Table 3 Nonnormalized Vastus Medialis 0bliquus:VastusLateralis Muscle (VM0:VL) .Integrated Electromyographic (IEMG) Ratios for Groups, Muscle Contraction Conditions,and Group x Condition interactionf Groupb ConditionC patterns. The patients with unilateral PFP had lower VM0:VL IEMG ratios for both knees than the VM0:VL IEMG ratios of the control subjects. This result supports the findings of Mariani and Caruso,: who reported decreased vastus medialis muscle EMG values in both knees of eight subjects with uni- 1 2 3 Means lateral subluxating patellae as com- pared with healthy subjects. The pres-CON 0.63r0.17 0.47?0.12 0.47-tO.13 0.54?0.16 ence of diminished VM0:VL IEMGECC 0.59r0.11 0.43rc_0.13 0.41 rc_O.ll 0.49rc_0.14 ratios in both knees o the patients fSIC 0.52r0.15 0.36-tO.09 0.38r0.11 0.44?0.14 with unilateral PFP suggests that ab-MIC 0.54r0.14 0.38?0.10 0.3420.10 0.4420.15 normal muscle activation patterns mayGroup me,ans 0.5720.1 4 0.41 r 0 . 1 2 0.40r0.12 interact with biomechanical factors in explaining the cause o unilateral PFP. f"Data are meansrstandard deviations for IEMG ratios formed by dividing nonnormalized VMO These factors might include unilateralIEMG value by nonnormalized vastus medialis muscle IEMG value. structural abnormalities (eg, leg- ~ r o u pl=healthy control subjects (both knees); group 2=patients with patellofemoral pain (af- length discrepancy, foot deformities,fected knees); group 3=patients with patellofemoral pain (unaffected knees). patellar asymmetry) or histories ofCCON=concentric quadriceps fenloris muscle contraction elicited during ascent of steps; activities that place asymmetrical de-ECC=eccentric quadriceps femoris muscle contraction elicited during descent of steps; mands on the lower extremities (eg,SIC=subm;utimal isometric quadriceps femoris muscle contraction; MIC=maximal isometric quad- running on a surface with a consistentriceps femoris muscle contraction. camber or a jumping sport that in- volves push-off with only one lower extremity). 10~20~21 Conclusions based on the effect of muscle contraction condition on VM0:VL IEMG ratio are independent of the previously identified dilemmas associated with normalization and electrode placement. All subjects con- tributed data to all conditions. The VM0:VL IEMG ratios for the isotonic conditions were greater than the VM0:VL IEMG ratios for the isometric contractions for both analyses. Differ- ences in VM0:VL IEMG ratios across activities may have important implica- tions under certain circumstances. If an abnormal VM0:VL activation pat- tern facilitates the development of PFP, then clinicians might identify a change in VM0:VL activation pattern as a goal of rehabilitation. A series of research questions is indicated in fol- 0.00 lowing this line of reasoning. Does a CON ECC MIC SIC consistent program of exercise involv- ing activities that elicit relatively large CONDITION VM0:VL IEMG ratios cause an in- crease in VM0:VL IEMG ratios for Figure 2. Nonnormalized uasttcs medialis ob1iquus:uastuslateralis muscle those activities? Does this effect trans- (VM0:VL)integrated electromyographic (IEMG) ratios. 0=group I , healthy control sub- fer to other activities or exercises thatjects (both knees); =group 2, patients with patellofemoral pain (affected knees); elicited relatively low VM0:VL IEMG O=group .?, patients with patellofemoral pain (unaffected knees). CON=concentric iso- ratios prior to initiation of the exer-tonic quadricepsfemoris muscle contraction performed during the ascent of a step;ECC=eccaztric isotonic quadriceps femoris muscle contraction performed during the cise program? Does the exercise pro-descent of a step; MIC=maximal isometric quadriceps femoris muscle contraction; gram also cause a reduction in pain SIC=submtucimal isometric quadricepsfemoris muscle contraction.Physical Therapy/Volume 71, Number 4 /April 1991
  7. 7. -Table 4. Analysis-of-Variance Results f o r Effects o f Group and Condition o nNonnorrnalized Vastus Medialis 0bliquus:Vastus Lateralis hluscle IntegratedElectromyographic RatiosSource df SS MS F 3 Insall]. Current concepts review: patellar pain. J Bone Joint Sulg (Am]. 1982;64:147-152. 4 Huherti HH, Hayes WC. Patellofemoral con- tact pressures: the influence of Q-angle and tendofemoral contact. J Bone Joint S u q (Am]. 1984;66:715-724. 5 Ficat R, Hungerford D. Disorders of the Pa- tellofemoral Joint. Baltimore, Md: Williams & Wilkins; I 977. 6 Wiberg G. Roentgenographic and anatomic studies on the femoropatellar joint. Acta Or-Between subjects thop Scand. 1941;12:319-410. Group 2 7 Mariani P, Caruso I. An electromyographic Error 29 investigation of subluxation of the patella. J Bone Joint Surg (Br]. 1979;61:169-171.Within subjects 8 Wild J, Franklin T, Woods W. Patellar pain Condition 3 and quadriceps rehabilitation: an EMG study. Am] Sports Med 1982;10:12-15. Condition x group 6 9 Moller B, Krrbs B, Tidemand-Dal C, h r i s K. Error 87 Isometric contractions in the patellofernoral pain syndrome. Arch Orlhop Trauma Sutg. 1986;105:24-27. 10 Levine J. Chondromalacia patellae. The Phy- sician and Sporlsmedicine. 1979;7:41-49. 11 Darling DJ. A Comparison of the Electro- myographic Activity of the Vastus Medialis andlevels and differences in the arthroki- ists and whether this difference has an Vastus Lateralis Muscles During Three Types ofnematics of the patellofemoral joint? effect on PFP etiology. Exercises in Patients with Chondromalacia Patellae. Chapel Hill, NC: The University of Nonh Carolina at Chapel Hill; 1984. MastersThe r e s u l ~ indicate that the isotonic Conclusions thesis.quadriceps femoris muscle contrac- 12 Blanpied P. The Effects of a Shorl-Arctions in this study elicited greater The results of this study suggest that Quadricep Strengthening Program o n [he EMGVM0:VLIEMG ratios than did isomet- individuals with PFP may differ from Activity of the Vastus Medialis Oblique and the Vastus Lateralis Muscles. Chapel Hill, NC: Theric quadriceps femoris muscle con- healthy individuals with regard to University of Nonh Carolina at Chapel Hill;tractions. Clinicians may be tempted VM0:VL activation patterns. This factor 1984. Masters thesis.to apply this information in treating may interact with biomechanical fac- 13 Hunter H. Patellofemoral anhralgia. JAmpatients who have PFP by using iso- tors in explaining the cause of PFP Osteop Arsoc. 1985;85:581-585. 14 Hoppenfeld S. Physical Examination of thetonic rather than isometric quadriceps syndrome. The isotonic quadriceps Spine and Ekfremities. New York, NY:femoris muscle contractions in treat- femoris muscle contractions tested in Appleton-Century-CroRs; 1976:191-192.ment regimens. We caution that the this study elicited larger VM0:VL 15 Stratford P. Electromyography of the quad-previously identified research ques- IEMG ratios than did the isometric riceps femoris muscles in subjects with normal knees and acutely e h s e d knees. Phys Ther.tions should be addressed prior to quadriceps femoris muscle contrac- 1981;62:279-283.concluding that such treatment plan- tions. This result suggests the need 16 Basmajian JV, Blumenstein R. Electrodening decisions are appropriate. for a series of studies to investigate Placemenl in EMG Biofeedback. Baltimore, the efficacy of different exercise pro- Md: Williams & Wilkins, 1980. 17 Lieb FJ, Perry J. Quadriceps function: anA final point for discussion concerns grams for the treatment of PFP. anatomical and mechanical study using ampu-the gender distribution of subjects in tated limbs. J Bone Joint Sulg (Am].this study. Most of the patients with 1968;50:1535-1548.unilateral PFP in this study were References 18 Goodfellow J, Hungerford D, Zindel M. Patello-femoral joint mechanics and patholow.women. Most of the subjects in the 1 Fox TA. Dysplasia of the quadriceps mecha- J Bone Joint Surg (Am]. 1976;58:287-290. - -control group were men. We are un- ,. nism: h v ~ o ~ l a sof the vastus medialis muscle a ia as related to the hypermobile patella syn- 19 Soderberg GL, Cook TM. Electromyogra-aware of any data that suggest a gen- phy in biomechanics. Phys Ther. 1984,64:1813- drome. S u p Clin North Am. 1975;55:199-226. 1820.der difference in VM0:VL activation 2 Bigos S, McBride G. The isolated lateral reti- 20 Corrigan B, Maitland GD. Practical Orlho-patterns. Future studies may indicate nacular release in the treatment of patellofem- paedic Medicine. 4th ed. London, England:whether such a gender difference ex- oral disorders. Clin Orthop. 1984;186:75-80 Butterworth & Co (Publishers) Ltd; 1987:155. 21 Macnicol MF. The Problem Knee: Diagnosis and Management in the Young Palient. Rock- ville, Md: Aspen Publishers Inc; 1986:105-107. Physical Therapy /Volume 71, Number 4 /April 1991

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