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 Table of Contents  
Year : 2022  |  Volume : 6  |  Issue : 1  |  Page : 18-22

Electromyography activity of quadratus lumborum in individuals with chronic knee osteoarthritis: A cross-sectional study

1 Department of Physiotherapy, Ramaiah Medical College, Bengaluru, Karnataka, India
2 Department of Physiotherapy, Ramaiah Memorial Hospital, Bengaluru, Karnataka, India

Date of Submission29-Oct-2021
Date of Acceptance11-Jan-2022
Date of Web Publication11-Mar-2022

Correspondence Address:
Mrs. Soni Srikantaiah
Department of Physiotherapy, Ramaiah Medical College, MSRIT Post, Bengaluru 560054, Karnataka.
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jsip.jsip_15_21

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Background: In osteoarthritis (OA) of the knee joint, a commonly seen gait alteration is lateral trunk lean gait. Quadratus lumborum (QL) has a role in controlling the pelvis and trunk during walking. This study has analyzed the electromyography (EMG) activity of QL muscle of the affected and nonaffected side during walking in individuals with chronic knee OA. Objectives: The objective of the study was to evaluate the muscle activation of QL in individuals with chronic knee OA during walking. Materials and Methods: EMG device, computer, video camera, abrasive gel (Nuprep gel), T20 paste, and two surface EMG triodes were used to record the QL muscle activity on the affected and nonaffected side. Twenty-seven patients with OA participated in the study. They were made to walk two rounds of 10 m distance and the EMG root mean square (RMS) value was noted down for both sides during the stance phase of the testing limb during walking activity. Results: Comparing the EMG activity of QL of the affected and nonaffected side, during the stance phase of walking, the result was found to be statistically nonsignificant, that is, P > 0.05. Conclusions: The results of this study found no difference in activity of QL in patients with OA between the affected and nonaffected sides.

Keywords: Compensatory gait, electromyography, gluteus medius weakness, osteoarthritis knee, quadratus lumborum

How to cite this article:
Pradhan S, Srikantaiah S, Mukhopadhyay A, Visweswara RD. Electromyography activity of quadratus lumborum in individuals with chronic knee osteoarthritis: A cross-sectional study. J Soc Indian Physiother 2022;6:18-22

How to cite this URL:
Pradhan S, Srikantaiah S, Mukhopadhyay A, Visweswara RD. Electromyography activity of quadratus lumborum in individuals with chronic knee osteoarthritis: A cross-sectional study. J Soc Indian Physiother [serial online] 2022 [cited 2023 Feb 7];6:18-22. Available from: http://www.jsip.ac.in/text.asp?2022/6/1/18/339426

  Introduction Top

Osteoarthritis (OA) is a degenerative joint disease that affects the elderly population.[1] OA develops and progresses due to various factors ranging from structural, biomechanical, genetic, and environmental.[2] The most common problems faced are pain, reduced range, muscle weakness, alteration of gait, and limitation of function. The degenerative changes in the knee are more frequently seen in the medial compartment than lateral.[3] It has been found that during walking, the knee joint loading, and kinematics is altered in individuals with knee OA, along with excessive loading on the medial compartment that is due to the increase in peak knee adduction moment and varus alignment of the knee joint. These factors further contribute to the progression of OA.[4],[5]

In chronic OA, over time in order to reduce the force vector, peak knee adduction moment and varus alignment, the trunk leans toward the lateral side during walking. The acquired compensatory trunk lean occurs toward the stance leg during walking.[5],[6],[7] A trunk lean gait is said to occur in OA of knee due to hip abductor muscle weakness mainly gluteus medius (GM).[7] If the hip abductor is weak, the pelvis will drop to the unsupported side during walking which is referred to as Trendelenburg gait.[8] During this time a compensatory lateral lean of the trunk over the pelvis toward the stance limb is observed. This happens to reduce the moment arm of the hip abductor, sufficient to stabilize the pelvis and shift the line of gravity on the supported limb.[8],[9]

A study analyzed the gait of individuals with medial compartment knee OA, where it was found that there was a greater hip and knee adduction moment to move the trunk laterally during walking.[6] As mentioned earlier, in lateral trunk lean gait or Trendelenburg gait the pelvis is rather weakly supported by the hip abductor which is not enough to stabilize the overlapping trunk.[10] A few studies also concluded that the compensation of gait pattern was a possible solution to reduce the mediolateral distance between the center of mass and the knee joint.[6],[11] The lateral trunk lean angle has been found to be about 3.0° ± 2.0° in subjects with knee OA.[12] On the contrary to lateral trunk lean angle, another study found that people with knee OA walked with higher trunk flexion of 2.5°–3° in sagittal plane rather than in frontal plane.[13]

QL is one of the back muscles which acts as lumbar stabilizer during bilateral contraction and as an ipsilateral lateral flexor of lumbar spine with unilateral contraction.[14] QL is a laterally placed back muscle and is said to produce a small force of 10 N during extension of lumbar spine as compared to 100 N and about 150 N of erector spinae and multifidus, respectively. QL takes part with less than 10% or about 10 N force during lateral tilt of the trunk.[15] According to Janda while performing side-lying hip abduction if the GM is weak there is lateral pelvic tilt noted which is due to overactivity of the quadratus lumborum (QL).[16] In cases of chronic low back pain (LBP) there seems to be overactivity with trigger points over QL. In addition, the role of QL changes from pelvic stabilizer to prime mover due to insufficiency of GM.[16],[17],[18]

During walking, the primary role of GM is to stabilize the pelvis throughout the stance phase.[19] Therefore individuals with weak GM will tend to lean the trunk laterally towards the side of the weak GM limb as mentioned in the above studies. Janda[16] and Cynn et al.[20] have explained a relationship between weak GM and synergist overactivity of QL in LBP individuals, a similar relation could also be seen in compensatory gait changes in knee OA individuals leading to lateral trunk gait.[16],[20] These muscles are an important variable to consider in the evaluation and treatment of chronic OA knee.[11] There is limited literature available which have assessed the QL activity in people with OA, hence this study aims to assess electromyography (EMG) activity of QL during walking in individuals with a unilateral or bilateral OA knee.

  Subjects and Methods Top

With the confidence interval of 95%, power of 80 and effect size of 0.5 based on pilot study and literature reviews, the sample size was estimated to be 27. The participants included were between the age of 45 to 70 years diagnosed with knee OA, with grades 2 and 3 on Kellgren–Lawrence scale. Participants were included if they had symptoms for over 6 months. Both unilateral and bilateral osteoarthritic participants were included. In participants with bilateral OA the knee which was more painful was considered as the affected leg.[11] Subjects were excluded if they were diagnosed with rheumatoid arthritis, gout, traumatic knee, or any lower limb or low back surgeries. The data were collected from July 2018 to July 2019, at the outpatient department of Ramaiah Hospitals, Bengaluru.

Computer, video camera, measuring tape, abrasive gel (Nuprep gel), T20 paste, and two surface EMG triodes were used to record the EMG data from the QL.

EMG device configuration

EMG signals were collected with the sampling rate at 2048 using encoder. The raw signal was filtered using a Butterworth fourth-order filter and Band passed between 10 and 500 Hz. To reduce the harmonics, a notch filter of 50 Hz was added to eliminate line noise. The collected EMG data were converted to root mean square (RMS) at 20 samples denoted as microvolts (µV) in RMS.

Procedure of data collection

Ethical clearance was obtained from the institutional ethics committee. The study was explained to each participant and written informed consent was obtained from the participants.

The surface marking of QL for electrode placement (according to Cynn et al.[20]) is about 4 cm lateral from the erector spinae belly and at half the distance between 12th rib and the iliac crest. With the patient in prone lying, the skin area was prepared by cleaning with Nuprep gel and a surface electrode was attached [Figure 1]. In a well-lit room, a video camera was set up to record the walking task. 10 m distance was marked on the floor and the participants were asked to walk for two rounds at their comfortable pace.
Figure 1: Surface marking and surface EMG electrode placement for QL

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Data recording and temporal windowing of the date

The data from the gait were windowed so that only stance phases of each limb could be analyzed. From the recorded video, the start of the stance phase was identified as toe off from the ground of the opposite leg. The end of the stance phase activity was identified as pre heel strike of the opposite leg. This was done for the affected and nonaffected leg of each participant. The peak amplitude activity of QL muscle on each side was identified throughout the stance phase of walking activity.

  Results Top

Of 27 participants, 8 were males and 19 females, among them 12 had unilateral knee OA and the rest 15 had bilateral knee OA. Their demographic details including age, weight, height, and duration of pain were recorded [Table 1].
Table 1: Demographic data

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The data distribution was nonuniform and hence non -parametric test: Mann–Whitney U test was used to analyze the significance level of the recordings. The EMG activity of QL of the affected and nonaffected side was compared, during stance phase of walking when the other leg was at early swing, midswing, and late swing (identified with the recorded video). There was no significant difference in the EMG activity in early swing, midswing, and late swing [Table 2] between affected and nonaffected sides (P > 0.05).
Table 2: Comparison of quadratus lumborum EMG activity between affected and unaffected side

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Another analysis was done to compare the total work (area under curve) done by QL of the affected side and nonaffected side throughout the stance phase of that particular limb. The area under the curve corresponds to the total amount of action potentials of QL muscles throughout that point of activity, that is, throughout the stance phase. There were no significant difference found between the total work done by the QL of the affected and nonaffected side, that is, P = 0.961 (P > 0.05) and the mean (standard deviation [SD]) was found to be 24.34(37.29) and 15.75(6.2), respectively.

  Discussion Top

This study evaluated the surface EMG activity of QL in individuals with chronic knee OA. The main objective of the study was to assess and compare the QL activity between the affected and unaffected side of the same individual during the stance phase of the gait cycle.

The EMG recording (in RMS) was taken at the point of stance phase when the contralateral limb was at early swing, midswing, and late swing. The results from comparison did not show a significant difference in QL activity between the affected and unaffected side. The participants in the study were within 2- 3 KL grade and individuals with 4 KL grade did not take part as they were either wheelchair bound or walking with assistive devices. As mentioned by Mündermann et al.[6] that individuals with low KL grade of knee OA have sufficient strength of hip abductor muscles to maintain the altered position of the trunk during walking activity which could be a possible explanation about less or no significant change in QL activity during walking. The result can also be explained with the reference to a gait analysis study done by Cassandra Herman where the gait difference between the individuals with unilateral knee OA and bilateral knee OA was found to be symmetrical. Herman found no differences in the kinematics, time, and kinetic variables of hip, knee, and ankle during gait analysis between the two groups. As there was no conclusion about a significant change on the affected lower limb joints, there would probably be no changes noted at pelvis and trunk level also.[21] Interestingly in a biomechanical study by Philips et al.[15] showed that only 10% or 10 N force is produced by QL during lateral tilt of the trunk which is a small force compared to the activity of erector spinae and multifidus, that is, 100 N and 150 N, respectively. Hence we assume that QL may not be significantly active on the affected side and there may be contribution from the other lateral spinal muscles. Therefore, our results showed no significant difference in QL activity between both sides in knee OA participants.

The second set of data recording was the area under the curve in µV/cm2 which reflected the total amount of work done by the QL muscle of each limb, throughout the stance phase of walking. No significant difference was found between the total work done by the QL of the affected and nonaffected side, that is, P = 0.961 (P > 0.05). Though no statistically significant result was found in total work done by QL, there was a slightly higher mean difference of 8.59 μV/cm2 on the affected side than nonaffected side during the stance phase of walking. As 3° ± 2° is a small value to cause a minimal trunk lean gait in knee OA participants,[12] this can be related to the slightly higher mean difference on the affected side compared to nonaffected side during stance phase of walking. Also a study by Preece et al.[13] concluded that people with knee OA group walked with higher trunk flexion of 2.5°–3° in a sagittal plane rather than in frontal plane. There are contributions from other muscles during walking activity besides QL and the role of other trunk and lower limb muscles could not be ruled out in our study. This could also mean that the total work mean difference of 8.59 μV/cm2 done by QL on the affected side was enough to cause minimal lateral trunk gait throughout the stance phase of walking. The limitation of the study was that QL being a deep muscle the surface EMG may not capture the activity of the muscle accurately and also the participants included were within 2 and 3 KL grade (mild to moderate) of knee OA with minimal trunk lean. Future studies could assess and compare EMG activity of QL and GM during walking.


In individuals with chronic knee OA, it has been found that there is reduced GM activity leading to altered gait patterns, especially trunk lean. QL is known to be a lateral flexor of the trunk. On assuming a hypothesis of alteration in QL activity on the affected side of knee OA rather than the nonaffected side, the study aimed at assessing the QL activity during walking in people with OA knee. The EMG activity of QL did not differ significantly between the affected and nonaffected limb. Though individuals walked with minimal-to-moderate lateral trunk lean in this study, the surface EMG could not record this minimal difference between affected side and nonaffected side.


We thank the Principal and Dean of Ramaiah Medical College and Hospitals, HOD of Department of Physiotherapy for providing their valuable support and continuous encouragement during the study. We also thank all the faculty members of the Department of Physiotherapy for their timely guidance and advice rendered during the study period.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

  References Top

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Favre J, Jolles BM. Gait analysis of patients with knee osteoarthritis highlights a pathological mechanical pathway and provides a basis for therapeutic interventions. EFORT Open Rev 2016;1:368-74.  Back to cited text no. 2
Oliveria SA, Felson DT, Reed JI, Cirillo PA, Walker AM. Incidence of symptomatic hand, hip, and knee osteoarthritis among patients in a health maintenance organization. Arthritis Rheum 1995;38:1134-41.  Back to cited text no. 3
Vincent KR, Conrad BP, Fregly BJ, Vincent HK. The pathophysiology of osteoarthritis: A mechanical perspective on the knee joint. Pm R 2012;4:S3-9.  Back to cited text no. 4
Chang A, Hayes K, Dunlop D, Song J, Hurwitz D, Cahue S, et al. Hip abduction moment and protection against medial tibiofemoral osteoarthritis progression. Arthritis Rheum 2005;52:3515-9.  Back to cited text no. 5
Mündermann A, Dyrby CO, Andriacchi TP. Secondary gait changes in patients with medial compartment knee osteoarthritis: Increased load at the ankle, knee, and hip during walking. Arthritis Rheum 2005;52:2835-44.  Back to cited text no. 6
Valente G, Taddei F, Jonkers I. Influence of weak hip abductor muscles on joint contact forces during normal walking: Probabilistic modeling analysis. J Biomech 2013;46: 2186-93.  Back to cited text no. 7
Norkin CC, Levangie PK. Joint Structure & Function: A Comprehensive Analysis. 5th ed. Philadelphia, PA: FA Davis Company; 2011.  Back to cited text no. 8
Hunt MA, Wrigley TV, Hinman RS, Bennell KL. Individuals with severe knee osteoarthritis (OA) exhibit altered proximal walking mechanics compared with individuals with less severe OA and those without knee pain. Arthritis Care Res (Hoboken) 2010;62:1426-32.  Back to cited text no. 9
Gandbhir VN, Lam JC, Rayi A. Trendelenburg gait. StatPearls [Internet].Treasure Island, FL: StatPearls Publishing; 2021 .  Back to cited text no. 10
Bechard DJ, Birmingham TB, Zecevic AA, Jones IC, Giffin JR, Jenkyn TR. Toe-out, lateral trunk lean, and pelvic obliquity during prolonged walking in patients with medial compartment knee osteoarthritis and healthy controls. Arthritis Care Res (Hoboken) 2012;64:525-32.  Back to cited text no. 11
Tokuda K, Anan M, Takahashi M, Sawada T, Tanimoto K, Kito N, et al. Biomechanical mechanism of lateral trunk lean gait for knee osteoarthritis patients. J Biomech 2018;66:10-7.  Back to cited text no. 12
Preece SJ, Algarni AS, Jones RK. Trunk flexion during walking in people with knee osteoarthritis. Gait Posture 2019;72:202-5.  Back to cited text no. 13
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Phillips S, Mercer S, Bogduk N. Anatomy and biomechanics of quadratus lumborum. Proc Inst Mech Eng H: J Eng Med 2008;222:151-9.]  Back to cited text no. 15
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Cynn HS, Oh JS, Kwon OY, Yi CH. Effects of lumbar stabilization using a pressure biofeedback unit on muscle activity and lateral pelvic tilt during hip abduction in sidelying. Arch Phys Med Rehabil 2006;87:1454-8.  Back to cited text no. 20
Herman C. Differential Effects of Unilateral Versus Bilateral Knee Osteoarthritis on Gait. Winston-Salem, NC: Wake Forest University; 2012.  Back to cited text no. 21


  [Figure 1]

  [Table 1], [Table 2]


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