Delayed onset of electromyographic activity of vastus medialis obliquus relative to vastus lateralis in subjects with patellofemoral pain syndrome

OBJECTIVE: To determine whether electromyographic (EMG) onsets of vastus medialis obliquus (VMO) and vastus lateralis (VL) are altered in the presence of patellofemoral pain syndrome (PFPS) during the functional task of stair stepping. DESIGN: Cross-sectional. SETTING: University laboratory. PATIENTS: Thirty-three subjects with PFPS and 33 asymptomatic controls. INTERVENTIONS: Subjects ascended and descended a set of stairs-2 steps, each 20-cm high-at usual stair-stepping pace. EMG readings of VMO and VL taken on middle stair during step up (concentric contraction) and step down (eccentric contraction). MAIN OUTCOME MEASURES: Relative difference in onset of surface EMG activity of VMO compared with VL during a stair-stepping task. EMG onsets were determined by using a computer algorithm and were verified visually. RESULTS: In the PFPS population, the EMG onset of VL occurred before that of VMO in both the step up and step down phases of the stair-stepping task (p <.05). In contrast, no such differences occurred in the onsets of EMG activity of VMO and VL in either phase of the task for the control subjects. CONCLUSION: This finding supports the hypothesized relationship between changes in the timing of activity of the vastimuscles and PFPS. This finding provides theoretical rationale to support physiotherapy treatment commonly used in the management of PFPS.     

Outcomes of a weight-bearing rehabilitation program for patients diagnosed with patellofemoral pain syndrome

OBJECTIVE: To determine the effects of a weight-bearing rehabilitation program on quadriceps and gluteus medius electromyographic activity, pain, and function in subjects diagnosed with patellofemoral pain syndrome (PFPS). DESIGN: Pretest and posttest 6-week intervention study. SETTING: Musculoskeletal research laboratory. PARTICIPANTS: Fourteen subjects diagnosed with PFPS and 14 healthy control subjects volunteered to participate in this study. No subjects withdrew from the study because of adverse effects. INTERVENTION: Subjects diagnosed with PFPS participated in a 6-week rehabilitation program. The rehabilitation program consisted of weight-bearing exercises that focused on strengthening the quadriceps and hip abductor musculature. MAIN OUTCOME MEASURES: Electromyographic onsets of the vastus medialis oblique (VMO) and vastus lateralis and onset and duration of the gluteus medius were collected during a stair-stepping task that was performed during the pretest and posttest. A visual analog scale (VAS) and Functional Index Questionnaire (FIQ) were administered at pretest and posttest and each week of the intervention. RESULTS: Vastus lateralis and VMO onset timing differences (vastus lateralis electromyographic onset minus VMO electromyographic onset) and VAS and FIQ scores significantly improved for patients diagnosed with PFPS. Vastus lateralis and VMO onset timing in the PFPS group were significantly different from those in the control group at baseline and were not significantly different from the control group after the intervention. We did not find differences in gluteus medius onsets or duration of activity. CONCLUSIONS: Subjects diagnosed with PFPS responded favorably and quickly to a therapeutic exercise program that incorporated quadriceps and hip musculature strengthening. The efficacy of the therapeutic exercise program used in this study should be further investigated in a larger subject population.     

Vastus medialis obliquus and vastus lateralis activity in open and closed kinetic chain exercises in patients with patellofemoral pain syndrome: an electromyographic study

OBJECTIVES: To evaluate the electromyographic activities of vastus medialis obliquus (VMO) and vastus lateralis (VL) muscles in open and closed kinetic chain exercises in subjects with patellofemoral pain syndrome (PFPS). DESIGN: Case-controlled study. SETTING: Rehabilitation science center in a tertiary medical center. PARTICIPANTS: Ten patients with bilateral knee pain diagnosed with PFPS and 10 healthy volunteers. INTERVENTIONS: Subjects performed open kinetic chain exercise on an isokinetic dynamometer and closed kinetic chain exercise by squat-to-stand and stand-to-squat tasks. Surface electromyography was done for the VMO and VL muscles. MAIN OUTCOME MEASURES: VMO/VL ratios were calculated after normalization of muscle activities. RESULTS: The VMO/VL ratios of PFPS subjects were significantly lower than were those of unimpaired subjects during knee isokinetic closed kinetic chain exercises (p = .047). However, there was no statistical difference in VMO/VL ratio between subjects with and without PFPS during closed kinetic chain exercises (p = .623). Maximum VMO/VL ratio was obtained at 60 degrees knee flexion in closed kinetic chain exercise. CONCLUSION: In closed kinetic chain exercises, more selective VMO activation can be obtained at 60 degrees knee flexion. Maximal VMO/VL ratio was observed at this knee flexion angle, and muscle contraction intensity was also greatest.     

表面肌电仪对髌股疼痛综合征患者膝关节肌电活动的分析

目的利用表面肌电仪分析髌股疼痛综合征患者康复训练前后股内侧斜肌（VMO）和股外侧肌（VL）肌电活动的变化。方法26例髌股疼痛综合征患者随机分为神经肌电生物反馈训练组（A组）和单纯训练组（B组）各13例，均接受相同的家庭训练，但A组患者在神经肌电生物反馈仪配合下进行训练。所有患者在开始训练前和训练8周后，利用表面肌电仪对VMO和VL的神经肌肉电活动进行连续6h评定，同时对膝关节疼痛程度进行评定。结果治疗后，B组患者的VMO／VL神经肌电比率与治疗前比较差异无显著性意义（P〉0．05），而A组患者的VMO／VL神经肌电比率与治疗前比较差异有显著性意义（P〈0．05）。结论采用神经肌电生物反馈仪配合髌股疼痛综合征患者的康复训练可促进股内侧斜肌的募集。     

Electromyographic fatigue characteristics of the quadriceps in patellofemoral pain syndrome

This study compared the fatigue characteristics of the vastus medialis oblique (VMO), vastus lateralis (VL) and rectus femoris (RF) muscles. Ten healthy subjects with 10 patients with patellofemoral pain syndrome (PFPS) performed an isometric leg press for 60 seconds at 60% MVIC with data collected using surface EMG. The power spectrum was analyzed and the extracted median frequency normalised to calculate a linear regression slope for each muscle. A repeated measures ANOVA revealed no significant differences, neither between the groups (P=0.592) nor the muscles (P=0.434). However, the slopes for the VMO and VL were different between the two groups with similar slopes for the RF. There was much larger variability of MF values in the PFPS group. The VMO:VL ratio calculated from these slopes for the healthy subjects was 1.17 and for the PFPS group was 1.78. These results may indicate unusual features in the fatigue indices of the quadriceps in PFPS.     

Ankle positioning and knee perturbation affect temporal recruitment of the vasti muscles in people with patellofemoral pain

Objectives

To compare the temporal recruitment of the vastus medialis obliquus (VMO) and vastus lateralis (VL) during voluntary ankle movements and perturbed standing in people with patellofemoral pain, and to determine the effects of different reflex and voluntary postural exercise tasks on VMO facilitation.

Design

Repeated-measures design.

Participants

Twenty-three subjects with patellofemoral pain.

Interventions

Quadriceps reflex contraction in response to postero-anterior knee perturbations was measured with three crural muscle contraction conditions and three postural exercises (semi-squatting, tip-toeing and heel standing).

Main outcome measures

The electromyographic (EMG) onset time of the VMO and VL during each task was measured and compared across the different tasks.

Results

The mean EMG onset time of the VMO was later than that of the VL in the voluntary tasks such as tip-toeing (VMO 95.3 ms vs VL 36.4 ms, mean difference 58.9 ms, 95% confidence interval −33.7 to 151.5 ms), whereas earlier VMO activation was found in the perturbation tests such as toe standing (VMO 17.6 ms vs VL 22.9 ms, mean difference −5.3 ms, 95% confidence interval −25.3 to 14.7 ms).

Conclusion

These findings suggest the potential benefits of unexpected perturbation activities for facilitating VMO activation. The clinical applications of perturbation tasks in rehabilitation exercise programmes and the underlying mechanisms warrant further investigation.     

Motor unit synchronization of the vasti muscles in closed and open chain tasks

OBJECTIVES: To investigate motor unit synchronization between medial and lateral vasti and whether such synchronization differs in closed and open chain tasks. DESIGN: Electromyographic recordings of single motor unit action potentials were made from the vastus medialis obliquus (VMO) and multiunit recordings from vastus lateralis during isometric contractions at 30 degrees of knee flexion in closed and open chain conditions. SETTING: Laboratory. PARTICIPANTS: Five volunteers with no history of knee pain (age, 30+/-3.32 y). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURE: The degree of synchronization between motor unit firing was evaluated by identifying peaks in the electromyographic averages of the vastus lateralis, triggered from motor unit action potentials in the VMO, and the proportion of power in the power spectral density of the triggered average at the firing frequency of the reference motor unit. The proportion of cases in which there was significant power and peaks in the triggered averages was calculated. RESULTS: The proportion of trials with peaks in the triggered averages of the vastus lateralis electromyographic activity was greater than 61.5% in all tasks, and there was a significantly greater proportion of cases where power in the spectrum was greater than 7.5% ( P =.01) for the closed chain condition. CONCLUSIONS: There was a high proportion of synchronized motor units between the 2 muscles during isometric contractions, with evidence for greater common drive between the VMO and vastus lateralis in closed chain tasks. This has implications for rehabilitation because it suggests that closed chain tasks may generate better coordination between the vasti muscles.     

COMPARISON OF HIP AND KNEE STRENGTH AND NEUROMUSCULAR ACTIVITY IN SUBJECTS WITH AND WITHOUT PATELLOFEMORAL PAIN SYNDROME

Purpose/Background:

Historically, patellofemoral pain syndrome (PFPS) has been viewed exclusively as a knee problem. Recent findings have suggested an association between hip muscle weakness and PFPS. Altered neuromuscular activity about the hip also may contribute to PFPS; however, more limited data exist regarding this aspect. Most prior investigations also have not concurrently examined hip and knee strength and neuromuscular activity in this patient population. Additional knowledge regarding the interaction between hip and knee muscle function may enhance the current understanding of PFPS. The purpose of this study was to compare hip and knee strength and electromyographic (EMG) activity in subjects with and without PFPS.

Methods:

Eighteen females with PFPS and 18 matched controls participated in this study. First, surface EMG electrodes were donned on the gluteus medius, vastus medialis, and vastus lateralis. Strength measures then were taken for the hip abductors, hip external rotators, and knee extensors. Subjects completed a standardized stair-stepping task to quantify muscle activation amplitudes during the loading response, single leg stance, and preswing intervals of stair descent as well as to determine muscle onset timing differences between the gluteus medius and vastii muscles and between the vastus medialis and vastus lateralis at the beginning of stair descent.

Results:

Females with PFPS demonstrated less strength of the hip muscles. They also generated greater EMG activity of the gluteus medius and vastus medialis during the loading response and single leg stance intervals of stair descent. No differences existed with respect to onset activation of the vastus medialis and vastus lateralis. All subjects had a similar delay in gluteus medius onset activation relative to the vastii muscles.

Conclusion:

Rehabilitation should focus on quadriceps and hip strengthening. Although clinicians have incorporated gluteus medius exercise in rehabilitation programs, additional attention to the external rotators may be useful.Level of Evidence: 4     

Effect of Weight-bearing Therapeutic Exercise on the Q-angle and Muscle Activity Onset Times of Elite Athletes with Patellofemoral Pain Syndrome: A Randomized Controlled Trial

[Purpose] The purpose of this study was to determine the effect of a weight-bearing therapeutic exercise program for elite athletes diagnosed as having patellofemoral pain syndrome (PFPS). [Subjects] The subjects were 34 elite athletes from the Seoul T Center. They were randomly allocated to three groups: an elastic band exercise group (EBG), a sling exercise group (SEG), or a control group (CG). [Methods] Therapeutic exercises were performed 3 times a week for 8 weeks. The visual analogue scale (VAS) hamstring length, and static and dynamic Q angles were used to test the exercise effect of the exercises, as well as the onset time of electromyographic activity of vastus medialis oblique (VMO) and vastus lateralis (VL). [Results] Decrease of the dynamic Q-angle in EBG was significant and significantly greater than that in CG. The decrease in VAS in SEG was significant and significantly greater than that in CG. There were significant differences in the VL and VMO activity onset times in SEG between pre- and post-test, and their differences between pre- and post-test were also significantly different. [Conclusion] Weight-bearing therapeutic exercise is hoped that clinicians will use this information for better implementation of effective exercise methods for elite athletes with PFPS.Key words: Electromyographic onset time, Patellofemoral pain syndrome, Q-angle     

Activation of vastus medialis oblique is not delayed in patients with osteoarthritis of the knee compared to asymptomatic participants during open kinetic chain activities

This study investigated whether the onset of electromyographic (EMG) activity of vastus medialis oblique (VMO) was delayed relative to that of vastus lateralis (VL) in patients with osteoarthritis (OA) of the knee compared to asymptomatic participants during open kinetic chain activities. An exploratory observational cross sectional study was carried out. Two groups were tested, symptomatic OA knee patients, diagnosed by an orthopaedic surgeon, (n=17), mean (SD) age 66.0 (7.6) years, and asymptomatic participants (n=17), 56.7 (8.6) years. Surface EMG activity of VMO and VL was measured, during concentric contractions extending the knee from 90 degrees flexion, and during maximal voluntary isometric contractions at 60 degrees knee flexion. The EMG onset times of VMO and VL were determined visually and by algorithm. The onset timing difference (OTD) between the two muscles was calculated for each subject, by subtracting the onset time of VL from VMO. Mann-Whitney U-tests revealed that the OTD between VMO and VL was not significantly different between the groups during either contraction type (both p>0.05). The results of this exploratory study may have implications for rehabilitation programmes aimed at developing preferential activation of VMO compared to VL in OA knee patients.     

Comparison of vastus medialis obliquus: vastus lateralis muscle integrated electromyographic ratios between healthy subjects and patients with patellofemoral pain

The purpose of this study was to compare vastus medialis obliquus:vastus lateralis muscle (VMO:VL) integrated electromyographic (IEMG) ratios of healthy subjects and patients with unilateral patellofemoral pain (PFP) under isotonic and isometric quadriceps femoris muscle contraction conditions. Subjects ranging in age from 18 to 35 years (mean = 28.06, SD = 5.97) were assigned to one of three groups on the basis of type of knee condition. In group 1, 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 comprised group 2, only the nonpainful knee was tested. Nonnormalized and normalized VMO:VL IEMG ratios were computed for ascending stairs, descending stairs, submaximal isometric contraction, and maximal isometric contraction (nonnormalized only). A two-way analysis of variance for repeated measures indicated VMO:VL ratios for isotonic stair-climbing activities were significantly greater than VMO:VL ratios for isometric contractions. Nonnormalized VMO:VL ratios in group 1 were significantly greater than nonnormalized VMO:VL ratios in the other two groups. Patients with PFP may have abnormal VMO:VL activation patterns, and isotonic quadriceps femoris muscle exercise may elicit more favorable muscle activation patterns than isometric exercise for patients with PFP.     

Contribution of components of the quadriceps femoris muscle for producing external torque in patients with patellofemoral pain syndrome

IntroductionDifferent muscular activities of the quadriceps components for producing necessary torque may change in patients with patellofemoral pain syndrome (PFPS). The aim of the current study, therefore, was to assess the contribution of each component of the quadriceps femoris muscle for producing external torque in patients with PFPS.MethodTwelve females with PFPS (24.7 ± 2.3 years) and twelve healthy matched females (25.4 ± 2.4 years) performed three consecutive knee flexion and extension movements with maximum effort at 45°/s and 300°/s using a Biodex system 3 dynamometer. Simultaneously, electromyographic (EMG) activities of the vastus medialis oblique (VMO), RF (rectus femoris) and vastus lateralis (VL) muscles were recorded using a DataLog instrument. Standard multiple regressions were used to assess the ability of EMG activities of the VMO, RF and VL muscles to predict normalized quadriceps femoris isokinetic concentric and eccentric torques at 45°/s and 300°/s in the normal and patient groups.ResultsIn the normal group, the VL and the VMO were the good predictors of quadriceps concentric torque at 45°/s and 300°/s, respectively. The VL and the RF were the good predictors of quadriceps eccentric torque at 300°/s in the patient group. No other conditions showed a considerable prediction for quadriceps torque in the normal or patient group.ConclusionFemales with PFPS differ with normal females in terms of the contribution of each component of the quadriceps femoris for producing external torque. Training the VMO for concentric contraction at both high and low velocities should be included in the management of the patients with PFPS.     

闭链与开链运动对髌股疼痛综合征股四头肌作用的表面肌电图研究

摘要 目的：利用表面肌电图(sEMG)对髌股疼痛综合征（patellofemoral pain syndrome, PFPS）患者双足半蹲伴或坐位伸膝动作下股四头肌进行评估,比较不同开链与闭链动作对股四头肌的作用差异。 方法：PFPS病例组及正常对照组各30例,分别在双足半蹲以及坐位伸膝动作时检测股外侧肌(vastus lateralis, VL)及股内斜肌（vastus medialis oblique, VMO）表面肌电图,分析时域、频域指标,比较其平衡关系。 结果：病例组双足半蹲动作与坐位伸膝动作时各肌电指标的VL/VMO比值在时域、频域指标均有显著性差异,在坐位单侧完全伸膝动作时VL/VMO肌电比值大于双足半蹲动作且>1。 结论：VL、VMO表面肌电指标在双足半蹲动作时较坐位单侧完全伸膝动作时更接近平衡,提示适当屈膝时的闭链运动能够更有选择性地激发VMO,这为PFPS的康复治疗的动作选择提供参考。     

Exercise effect on electromyographic activity of the vastus medialis oblique and vastus lateralis muscles

The purpose of this study was to determine whether the vastus medialis oblique muscle (VMO) had greater electrical activity than the vastus lateralis muscle (VL) when hip adduction and medial (internal) tibial rotation exercises were performed. Electrical activity of the VMO and VL was measured on 25 healthy subjects during maximal-effort isometric contractions of hip adduction and medial tibial rotation. The results showed that the electromyographic activity of the VMO was significantly greater than that of the VL during the hip adduction exercise. Differences noted with medial tibial rotation were not significant. The results suggest that the VMO may be selectively activated by performing hip adduction exercises. Resistive hip adduction exercises, therefore, may be advisable in the treatment of patients with lateral malalignment of the patella with accompanying pain or instability.     

A Study on the Differences of Quadriceps Femoris Activities by Knee Alignment during Isometric Contraction

[Purpose] This study attempted to identify how genu varum or valgum affects the electromyographic activities of the vastus medialis, vastus lateralis, and rectus femoris during knee isometric contraction. [Subjects] Fifty-two healthy young adults were enrolled in this study. They were enrolled and classified into three groups by knee alignment conditions: the genu varum, genu valgum, and control groups. [Methods] The electromyographic activity ratio of the vastus medialis to the vastus lateralis and rectus femoris were calculated using the percentage of maximum voluntary contraction. The participants contracted their quadriceps during isometric contraction at 30 and 60° of knee flexion. [Results] The genu varum group had more activity in the vastus medialis than in the vastus lateralis and rectus femoris, whereas the genu valgum group had more activity in the vastus lateralis and rectus femoris than in the vastus medialis. There was a significant difference in the muscle activity ratio between the vastus medialis and vastus lateralis by angle of knee flexion degree only in the genu valgum. There were no significant differences in any of the three groups in terms of the muscle activity ratio of the vastus medialis to the rectus femoris by angle of knee flexion. [Conclusion] The quadriceps femoris was used for different strategies according to knee alignment during isometric contraction at 30 and 60°. This study suggests that rehabilitation training programs used to strengthen the quadriceps should consider the knee alignment conditions of the target subjects.Key words: Electromyography, Quadriceps muscle, Isometric contraction     

Physiotherapy education in a digital era: blending and flipping

Abstract

The evidence base for changes in electromyographic (EMG) onset and intensity of vastus medialis (VM) and vastus lateralis (VL) in patients with patellar instability is systematically reviewed. The databases AMED, CINAHL, the Cochrane Library, EMBASE, Ovid Medline, Physiotherapy Evidence Database (PEDro), Pubmed and Zetoc were searched from their inception to March 2008, in addition to a manual search of relevant journals. All English-language papers assessing the relative EMG onset and intensity of vastus medialis oblique (VMO) and VL, in patients with patellar dislocation, subluxation and general instability were included. Five papers, consisting of 73 knees with patellar instability, were reviewed. No studies were identified assessing VMO–VL onset in patients with patellar instability. Four studies reported no difference in relative EMG intensity of VMO and VL in patients with patellar instability compared with asymptomatic control subjects. One study reported some evidence of a difference in VM to VL EMG intensity in one cohort of patients with patellar subluxation. The CASP appraisal of the evidence base highlighted a number of methodological weaknesses. There was no robust evidence for any difference in the relative intensity of EMG activity between the VMO and VL in patients with patellar instability. There is no good-quality research evidence to suggest that abnormal vastii EMG intensity or onset are aetiological factors associated with patellar instability.     

髌股关节疼痛及其临床治疗的研究

概述过去十年作者在实验室进行有关髌股关节及髌股关节疼痛综合征(PFPS)的研究,研究了正常人髌股关节的几个指标及PFPS患者的康复成效。研究结果反映股内侧肌(VMO)对于控制髌股关节的压力分布所发挥的力学作用、下肢方位对促进VMO募集的影响,以及髌骨叩压、股四头肌的疲劳恢复与生物反馈辅助对PFPS康复治疗的作用。     

Effects of feedback on activation of the quadriceps during weight-bearing tasks of the Wii

[Purpose] This investigation evaluated the effect of real-time feedback on electrical activation of the quadriceps during 3 weight-bearing tasks of the Wii Fit Plus^®. [Subjects] Thirty male healthy volunteers were recruited. [Methods] Activation of the vastus medialis, vastus lateralis, and rectus femoris muscles was recorded during virtual lunge, single leg extension, and single leg reach exercises. Each exercise was performed twice in 3 randomized experimental conditions (with visual feedback, with auditory feedback, and with no feedback). The normalized electromyographic data (using maximum voluntary isometric contraction) were analyzed using repeated measures analysis of variance and Tukey’s test. [Results] No significant difference was found in the muscles among the feedback conditions during the 3 exercises. However, the variation in the muscle activity of the vastus medialis and vastus lateralis (18.23–29.20% of maximum voluntary isometric contraction) was higher (47–62%) than that in the rectus femoris (7.35–12.98% of maximum voluntary isometric contraction). [Conclusion] Real-time feedback did not alter quadriceps activation during the Wii tasks. Additionally, these games showed electromyographic activation levels similar to those for the same tasks outside the virtual environment. The Wii weight-bearing tasks could therefore constitute a physical activity program but without the additional benefit of feedback.Key words: Electromyography, Functional exercises, Exergames     

EMG activity of the vastus medialis oblique and the vastus lateralis in their role in patellar alignment

Using intramuscular electrodes the integrated electromyographic activity of the vastus medialis oblique and the vastus lateralis was examined in twenty normal females. The activity was recorded during the last thirty degrees of distal segment stabilized knee extension, when patellar subluxation commonly occurs. The electromyographic activity was normalized and expressed as a percentage of a maximal isometric contraction. Both muscles exhibited low levels of activity with no significant differences between the two. This study provides a quantitative method to assess whether muscular imbalance is present in patients with patellar subluxation.     

Delayed onset of quadriceps activity and altered knee joint kinematics during stair stepping in individuals with knee osteoarthritis

OBJECTIVE: To determine if the electromyographic onset of vastus lateralis and kinematic knee joint motion in individuals with knee osteoarthritis (OA) differs from that of asymptomatic persons, during the task of stair stepping. DESIGN: Cross-sectional. SETTING: University laboratory in Australia. PARTICIPANTS: Twenty-five participants with symptomatic knee OA and 33 asymptomatic controls. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Surface electromyography to determine the onset of vastus lateralis activity. Two-dimensional kinematic analysis of sagittal plane knee motion during stance phase of stair ascent and descent. RESULTS: Participants with knee OA showed delayed onset of vastus lateralis activity during stair descent (P<.05) but not ascent. Both groups displayed a similar total range of knee motion. However, during stair descent, participants with OA had less knee flexion during early stance (P<.05) than controls. CONCLUSION: Individuals with knee OA display altered quadriceps function and knee joint kinematics during stair descent. These impairments may have implications for force attenuation across the knee joint and warrant future investigation.