Biofeedback exercise improved the EMG activity ratio of the medial and lateral vasti muscles in subjects with patellofemoral pain syndrome

Advancing clinical understanding of surface electromyography biofeedback: bridging research, teaching, and commercial applications

INTRODUCTION

Expanding the use of surface electromyography-biofeedback (EMG-BF) devices in different therapeutic settings highlights the gradually evolving role of visualizing muscle activity in the rehabilitation process. This review evaluates their concepts, uses, and trends, combining evidence-based research.

AREAS COVERED

This review dissects the anatomy of EMG-BF systems, emphasizing their transformative integration with machine-learning (ML) and deep-learning (DL) paradigms. Advances such as the application of sophisticated DL architectures for high-density EMG data interpretation, optimization techniques for heightened DL model performance, and the fusion of EMG with electroencephalogram (EEG) signals have been spotlighted for enhancing biomechanical analyses in rehabilitation. The literature survey also categorizes EMG-BF devices based on functionality and clinical usage, supported by insights from commercial sectors.

EXPERT OPINION

The current landscape of EMG-BF is rapidly evolving, chiefly propelled by innovations in artificial intelligence (AI). The incorporation of ML and DL into EMG-BF systems augments their accuracy, reliability, and scope, marking a leap in patient care. Despite challenges in model interpretability and signal noise, ongoing research promises to address these complexities, refining biofeedback modalities. The integration of AI not only predicts patient-specific recovery timelines but also tailors therapeutic interventions, heralding a new era of personalized medicine in rehabilitation and emotional detection.

The Role of Biofeedback in Patellofemoral Pain Conservative Treatment: A Systematic Review

This paper aims to investigate the effectiveness and the outcomes of the association between different types of biofeedback techniques and therapeutic exercises in the conservative treatment of patellar femoral pain (PFP). The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement guidelines have been used and followed the Cochrane Handbook for Systematic Reviews of Interventions. Between April and June 2023, the following electronic databases were searched: PubMed, ScienceDirect, BIOMED Central, Cochrane Library, and PEDro. Only randomized controlled trials (RCTs) were selected. Following the search, 414 records were found, and after using strict inclusion and exclusion criteria, 12 RCTs were retrieved to include in this systematic review, assessing 513 patients. The association between biofeedback and therapeutic exercise may be beneficial for pain, function (AKPS), extensor muscle strength, reduction of the dynamic knee valgus and vastus medialis (VM) and vastus lateralis (VL) (EMG) optimization. All these results were valued in the short term. Regarding the intervention type, it was possible to correlate the EMG biofeedback with the benefits of the knee extensor strength and the EMG activity of VM and VL. Conversely, using mirror, verbal, and somesthetic (hands and band) feedback seems to be linked to the reduction of the knee dynamic valgus.

Effects of Electromyographic Biofeedback-Assisted Exercise on Functional Recovery and Quality of Life in Patients after Total Hip Arthroplasty: A Randomized Controlled Trial

The goal of the trial was to examine the effects of adding electromyographic biofeedback (EMG-BF) to the conventional program of physiotherapy after total hip arthroplasty (THA) on functional recovery and quality of life. The trial was designed as a prospective, interventional, single-blinded randomized controlled study. Ninety patients were randomized into an experimental group (EG) (n = 45; mean age 63.9 ± 8.8) and control group (CG) (n = 45; mean age 63.9 ± 9). All patients received 21 days of physiotherapy which consisted of therapeutic exercise (land-based and aquatic), electrotherapy, and education. Electromyographic biofeedback was added to a portion of the land-based exercise in EG. The Hip Disability and Osteoarthritis Outcome Score (HOOS), Numeric Rating Scale (NRS), Short Form Health Survey-36 (SF-36), use of a walking aid, 30 s chair stand test (CST) as well as the Timed Up and Go (TUG) test were used for outcome measurement. A higher proportion of the participants in both groups did not need a walking aid after the intervention (p < 0.05). All participants improved their 30 s CST and TUG results (p < 0.001), as well as their NRS and HOOS scores (p < 0.05). No significant differences between the groups were found. There were no additional benefits from adding EMG-BF to the conventional physiotherapy protocol.

Recovery of Quadriceps Strength and Knee Function Using Adjuvant EMG-BF After Primary ACL Reconstruction

Introduction: Immobility and limited usage of operated limbs lead to weakness and atrophy of the muscle after anterior cruciate ligament (ACL) reconstruction. However, training programs for preventing biomechanical risk factors such as lower limb alignment and increased muscular contraction are very limited. Thus, the current study was carried out to evaluate the recovery of quadriceps muscle strength and the improvement of knee function using adjuvant electromyographic biofeedback (EMG-BF) after ACL reconstruction. Methods: This prospective randomized controlled trial was conducted among 40 patients (20=EMG-BF group, 20=Control group) with ACL reconstruction, who were referred to Akhtar Hospital from 2021 to 2022. In the EMG-BF group, EMG BFB was added to the standard rehabilitation protocol, and in the control group, the standard rehabilitation protocol with full postoperative weight-bearing, knee brace (zero degree of extension, 90 degrees of flexion), and electrical stimulation with maximal voluntary isometric knee extension was performed. Each group was intervened for 4 weeks and three sessions of 30 minutes per week. It should be noted that each patient participated in 16 outpatient physiotherapy sessions after surgery. Nicholas Hand-Held Dynamometer (HHD) was used for measuring quadriceps strength, and Knee Outcome Survey-Activities of Daily Living (KOS-ADLs) and Knee Outcome Survey Sports Activities Scale (KOS-SAS) questionnaires were used for assessing the knee function. Results: Four weeks after the treatment, the EMG-BF group showed a significant increase in quadriceps strength (P=0.0001). Quadriceps strength had a significant difference before and after 4 weeks of intervention (P=0.0001), but in the control group, no significant difference was observed (P=0.368). The EMG-BF group had a significant increase in KOS-ADLs and KOS-SAS scores after 4 weeks of intervention (P=0.0001). Conclusion: In our study, isometric strengthening of quadriceps with adjuvant EMG-BF significantly increased the strength of quadriceps and knee function during 4 weeks. EMG-BF is a low risk, low cost, and less invasive intervention and has high safety and adjustment ability. It is a valuable adjuvant method for achieving better functional recovery in a shorter time.

Is the attenuation effect on the ankle muscles activity from the EMG biofeedback generalized to - or compensated by - other lower limb muscles during standing?

Biofeedback based on electromyograms (EMGs) has been recently proposed to reduce exaggerated postural activity. Whether the effect of EMG biofeedback on the targeted muscles generalizes to - or is compensated by - other muscles is still an open question we address here. Fourteen young individuals were tested in three 60 s standing trials, without and with EMG-audio feedback: (i) collectively from soleus and medial gastrocnemius and (ii) from medial gastrocnemii. The Root Mean Square (RMS) of bipolar EMGs sampled from postural muscles bilaterally was computed to assess the degree of activity and postural sway was assessed from the center of pressure (CoP). In relation to standing at naturally, EMG-audio feedback from soleus and medial gastrocnemii decreased plantar flexors' activity (∼10 %) but at the cost of increased amplitude of tibialis anterior (∼5%) and vasti muscles (∼20 %) accompanied by a posterior shift of the mean CoP position. However, EMG-audio feedback from medial gastrocnemii reduced only plantar flexors' activity (∼5%) when compared to standing at naturally. Current results suggest the EMG biofeedback has the potential to reduce calf muscles' activity without loading other postural muscles especially when using medial gastrocnemii as feedback source, with implications on postural training aimed at assisting individuals in activating more efficiently postural muscles during standing.

Botulinum neurotoxin type A improves vasti muscle balance, patellar tracking, and pain in patients with chronic patellofemoral pain

The purpose of this study was to determine the effects of botulinum neurotoxin type A (BoNT-A) on vastus lateralis:vastus medialis (VL:VM) muscle balance, patellar tracking, and pain in patients with chronic patellofemoral (PF) pain. We recruited 13 participants (9 females, 4 males) with recalcitrant PF pain who underwent ultrasound-guided BoNT-A injections into the distal third of the VL muscle, followed by a 6-week home exercise program to strengthen their VM muscle. We imaged the participants in a C-arm computed tomography (CT) scanner before and after the intervention. We calculated VL:VM ratios from CT images from a supine, nonweight-bearing condition. We obtained patellar tilt and bisect offset values from CT images from an upright, weight-bearing condition. We recorded functional pain scores before, immediately after, and 2-4 years after the intervention. We classified the participants into normal tracking and maltracking groups based on their patellar tilt and bisect offset values. BoNT-A with home exercise reduced VL:VM ratio (18%; p < 0.001), patellar tilt (19%; p = 0.020), and bisect offset (5%; p = 0.025). Four participants classified as maltrackers before the intervention transitioned to normal tracking after the intervention. Functional pain scores improved immediately after the intervention (13%, p < 0.001) and remained improved at 2-year follow-up (12%, p = 0.011). Statement of Clinical Significance: This study provides new evidence in support of BoNT-A for treatment of PF pain. Classification of patients under weight-bearing conditions may identify individuals who will most benefit from a BoNT-A treatment.

Efficacy of Patellar Taping and Electromyographic Biofeedback Training at Various Knee Angles on Quadriceps Strength and Functional Performance in Young Adult Male Athletes with Patellofemoral Pain Syndrome: A Randomized Controlled Trial

Background

The severity of the articular lesion is the single most essential element in investigating the extent of flexion that is required for activities. However, a prior study found no differences in muscle strength gains of quadriceps muscles at different knee angles in people with patellofemoral pain syndrome (PFPS).

Objective

The effects of patellar taping and electromyographic biofeedback (EMG-BF)-guided isometric quadriceps strengthening at different knee angles (e.g., 30°, 60°, and 90° of knee flexion) on quadriceps strength and functional performance in people with PFPS were compared in this single-blind randomized controlled parallel trial.

Methods

Sixty adult male athletes with PFPS (age: 26.9 ± 1.4 years) were randomly divided into two groups. The experimental group (n = 30) received patellar taping and EMG-BF-guided isometric contraction exercise at 30°, 60°, and 90° angles, and the control group (n = 30) received sham patellar taping without EMG-BF-guided exercises for six weeks. Pain intensity, knee function, muscle strength, and the single-leg triple hop (SLTH) test were assessed.

Results

The pain intensity and SLTH scores between the groups were significantly different at the end of the trial (p ≤ 0.001). The EMG-BF and control groups had mean pain scores of 1.3 (0.8) and 4.5 (0.8), respectively. The EMG-BF and control groups had mean functional scores of 80.4 (5.1) and 69.1 (6.1), respectively. The mean SLTH score for the EMG-BF group was 540.7 (51.2) and for the control group it was 509.4 (49.8) after the trial. Quadriceps muscle strength was significantly higher in those who performed quadriceps strength training at 60° of knee flexion after six weeks than in those who performed strength training at 30° or 90° of knee flexion.

Conclusion

The findings indicated that individuals who trained their quadriceps at a 60° knee angle had significantly stronger quadriceps muscles than individuals who trained at 30° or 90° of knee flexion. Trial Registration. This trial is registered at Clinical Trials.gov under the identifier NCT05055284.

Muscle coordination retraining inspired by musculoskeletal simulations reduces knee contact force

Humans typically coordinate their muscles to meet movement objectives like minimizing energy expenditure. In the presence of pathology, new objectives gain importance, like reducing loading in an osteoarthritic joint, but people often do not change their muscle coordination patterns to meet these new objectives. Here we use musculoskeletal simulations to identify simple changes in coordination that can be taught using electromyographic biofeedback, achieving the therapeutic goal of reducing joint loading. Our simulations predicted that changing the relative activation of two redundant ankle plantarflexor muscles—the gastrocnemius and soleus—could reduce knee contact force during walking, but it was unclear whether humans could re-coordinate redundant muscles during a complex task like walking. Our experiments showed that after a single session of walking with biofeedback of summary measures of plantarflexor muscle activation, healthy individuals reduced the ratio of gastrocnemius-to-soleus muscle activation by 25 ± 15% (p = 0.004, paired t test, n = 10). Participants who walked with this “gastrocnemius avoidance” gait pattern reduced late-stance knee contact force by 12 ± 12% (p = 0.029, paired t test, n = 8). Simulation-informed coordination retraining could be a promising treatment for knee osteoarthritis and a powerful tool for optimizing coordination for a variety of rehabilitation and performance applications.

Effects of Electromyographic Biofeedback on Functional Recovery of Patients Two Months after Total Knee Arthroplasty: A Randomized Controlled Trial

The incidence of total knee arthroplasty (TKA) is steadily increasing worldwide. Therefore, it is crucial to develop efficient rehabilitation protocols and investigate the innovations in medical technology, which could improve rehabilitation outcomes. The aim of the study was to investigate the effect of adding electromyographic biofeedback (EMG-BF) to the conventional program of rehabilitation after TKA on quality of life, intensity of pain, and functional performance. The study was designed as a randomized controlled trial. A total of 131 patients were randomly assigned to two groups: an experimental group (n = 67; median age 70 (IQR 10)), and a control group (n = 64; median age 69 (IQR 9)). Both groups participated in an inpatient program of 21 days of rehabilitation, including land-based and aquatic exercise therapy, electrotherapy, and education. In the experimental group, a portion of land-based exercise therapy was supplemented by EMG-BF. A numeric rating scale (NRS), Knee Injury and Osteoarthritis Outcome Score (KOOS), use of mobility aids, 30 s chair stand test (CST), and timed up and go (TUG) test were used to measure outcomes. Both groups improved their functional abilities from day 1 to day 21 of rehabilitation. A higher proportion of participants did not use a walking aid (p < 0.002), and their NRS, KOOS, 30 s CST and TUG scores improved (p < 0.001). There were no significant differences between the groups in the outcomes. EMG-BF did not provide additional benefits to the conventional rehabilitation after TKA.

Electromyographic comparison of vastus medialis obliquus facilitatory versus vastus lateralis inhibitory kinesio taping in athletes with patellofemoral pain: A randomized clinical trial

BACKGROUND

Patellofemoral pain (PFP) is among the most common orthopedic complications afflicting active young people. Diminished coordination of the vastii, delayed activation of the vastus medialis obliquus (VMO), and decreased VMO-to-vastus lateralis (VL) activity ratio are well documented as underlying causes of PFP. This study compares the effects of VMO facilitatory kinesio tape (KT) versus VL inhibitory KT on electromyographic (EMG) activity of the vastii, balance, and pain in athletes with PFP.

METHODS

In this single-blind randomized clinical trial, thirty-two female athletes with PFP (mean age 26.33 ± 5.93 years) were randomly assigned to VMO facilitatory KT (n = 16) or VL inhibitory KT (n = 16) groups. In the facilitatory group, a Y-shaped strip of KT at 25% of its available tension was attached from the origin of the VMO to its insertion and in the inhibitory group, an insertion-to-origin Y-shaped strip of KT at 15% of its available tension was applied on the VL. Pain intensity, dynamic balance, and EMG data were assessed respectively with a visual analogue scale, the modified Star Excursion Balance Test, and an EMG telemetry system, before and immediately after KT application.

RESULTS

Pain intensity decreased and dynamic balance improved significantly after taping in both groups, and VMO: VL activity ratio increased significantly in the VL group. However, none of the parameters differed significantly between groups.

CONCLUSIONS

Both VMO facilitatory and VL inhibitory KT can improve pain and balance, while the inhibitory technique might be more effective in regulating the VMO to VL activity ratio in athletes with PFP.

Surface electromyography and gamification: Translational research to advance physical rehabilitation

Many problems that fall in medical domains of inquiry have behavioral components that can be optimized to increase benefits for patients. For example, although surgical intervention is effective in reducing the pain resulting from osteoarthritis of the knee, patients often struggle to regain complete functional use of the joint. In this translational study, we point to some ways in which behavioral contingencies of reinforcement are compromised, making the recovery process more difficult. We also report on the use of surface electromyography (sEMG) with healthy participants to create supplementary contingencies of reinforcement to support the development and maintenance of clinically relevant exercises. The procedures reported provide a proof-of-concept and can contribute to an increase in the systematic use of games and feedback in physical rehabilitation in recovery from knee surgery. The results of this translational study suggest an expanded role for applied behavior analysis in the domains of health and medicine.

Efficacy of Electromyographic-Biofeedback Supplementation Training with Patellar Taping on Quadriceps Strengthening in Patellofemoral Pain Syndrome among Young Adult Male Athletes

This study compares the effects of electromyographic-biofeedback (EMG-BF)-guided isometric quadriceps strengthening with patellar taping and isometric exercise alone in patellofemoral pain syndrome (PFPS) among young adult male athletes. Sixty young adult male athletes with PFPS participated in the study. Participants were randomly divided into two groups: (1) EMG-BF-guided isometric exercise training with patellar taping (experimental group, n = 30), and (2) sham EMG-BF training with an isometric exercise program (control group, n = 30). Participants conducted their respective exercise programs for five days per week across four weeks. Study outcomes were pain (measured by the visual analog scale), functional disability (measured by the Kujala Anterior Knee Pain scale), and quadriceps strength (measured by an ISOMOVE dynamometer). Measurements were taken at baseline, Week 2, Week 4, and during a follow-up at Week 6. The experimental group demonstrated significantly lower VAS score at Weeks 2 and 4 compared to that of the control group (p = 0.008 and 0.0005, respectively). The score remained significantly lower at the Week 6 follow-up compared to the control group (p = 0.0005). There were no differences in knee function at Weeks 2 and 4 between the two groups (p = 0.086 and 0.171, respectively); however, the experimental group showed significantly better knee function at Week 6 compared to the control group (p = 0.002). There were no differences in quadriceps strength at Week 2 between the two groups (p = 0.259); however, the experimental group demonstrated significantly higher quadriceps strength at Weeks 4 and 6 compared to the control group (p = 0.0008). Four weeks of EMG-BF supplementation training with patellar taping demonstrated significant improvements in pain intensity, functional disability, and quadriceps muscle strength in young adult male athletes with PFPS.

Effectiveness of therapeutic electromyographic biofeedback after orthopedic knee surgeries: a systematic review

PURPOSE

To present an evidence-based overview of the current utilization and the effectiveness of therapeutic Electromyographic Biofeedback (EMG-BF) in rehabilitation after orthopedic knee surgeries.

MATERIALS AND METHODS

This systematic review was conducted according to the PRISMA statement. MEDLINE (PubMed), PEDro, The Cochrane Library, and Web of Science databases were searched from their inception to June 20, 2020.

RESULTS

Eight RCTs investigating effectiveness of the EMG-BF in rehabilitation after orthopedic knee surgeries were identified. The quality scores for included studies ranged from 6 to 8 on PEDro Scale. Most of the included studies reported that EMG-BF was more effective compared to home exercises, standard rehabilitation program or electrical stimulation for improving quadriceps strength or activation. Besides, EMG-BF was revealed positive results in functional assessments except gait velocity and IKDC. Only two studies reported knee ROMs were significantly improved in favour of EMG-BF.

CONCLUSIONS

This systematic review shows that EMG-BF seems to control pain and improve quadriceps femoris strength and functionality. However, the results are inconclusive regarding knee ROMs. Although available high-quality evidence is limited, EMG-BF might be a part of the rehabilitation after knee surgeries.Implications for rehabilitationThis paper reviews the effectiveness of the therapeutic EMG-BF as a potential option in rehabilitation after orthopedic knee surgeries.It is recommended EMG-BF can be used to control pain and to improve quadriceps strength and function.There is insufficient evidence to support EMG-BF to improve the range of motion.

Comparison of muscle activation levels and knee valgus between individuals with medial patellofemoral ligament reconstruction and healthy individuals during fatiguing step down task

BACKGROUND

Medial patellofemoral ligament reconstruction becomes first-choice surgical procedure for patients with a history of lateral patellar dislocations but there is limited knowledge about neuromuscular activation patterns of individuals with a history of patellar dislocation who underwent medial patellofemoral ligament reconstruction.

OBJECTIVE

The aim of this study was to compare muscle activation levels and knee valgus during step down performance test between individuals with a history of medial patellofemoral ligament reconstruction and healthy individuals.

METHODS

Fifteen individuals with medial patellofemoral ligament reconstruction and 15 healthy individuals were included. Vastus medialis obliquus, vastus lateralis and gluteus medius muscle activation levels and knee valgus were measured during 60-s- step down performance test. Two-way repeated-measures of analysis of covariance was used for statistical analysis.

FINDINGS

Compared to the healthy individuals, individuals with medial patellofemoral ligament reconstruction showed lower vastus medialis obliquus (p = .04) and gluteus medius (p = .005) activation levels, and higher knee valgus (p = .002) in last period of the step down performance test.

INTERPRETATION

Since the significant results were only observed in the fatiguing section of the test, endurance tests may provide more information about neuromuscular control of the individuals with history of medial patellofemoral ligament reconstruction. Future studies should investigate whether endurance exercises that target to improve vastus medialis obliquus and gluteus medius activity result in better clinical outcomes than conventional programs for individuals with medial patellofemoral ligament reconstruction.

Coordination amongst quadriceps muscles suggests neural regulation of internal joint stresses, not simplification of task performance

Many studies have demonstrated covariation between muscle activations during behavior, suggesting that muscles are not controlled independently. According to one common proposal, this covariation reflects simplification of task performance by the nervous system so that muscles with similar contributions to task variables are controlled together. Alternatively, this covariation might reflect regulation of low-level aspects of movements that are common across tasks, such as stresses within joints. We examined these issues by analyzing covariation patterns in quadriceps muscle activity during locomotion in rats. The three monoarticular quadriceps muscles (vastus medialis [VM], vastus lateralis [VL], and vastus intermedius [VI]) produce knee extension and so have identical contributions to task performance; the biarticular rectus femoris (RF) produces an additional hip flexion. Consistent with the proposal that muscle covariation is related to similarity of muscle actions on task variables, we found that the covariation between VM and VL was stronger than their covariations with RF. However, covariation between VM and VL was also stronger than their covariations with VI. Since all vastii have identical actions on task variables, this finding suggests that covariation between muscle activity is not solely driven by simplification of overt task performance. Instead, the preferentially strong covariation between VM and VL is consistent with the control of internal joint stresses: Since VM and VL produce opposing mediolateral forces on the patella, the high positive correlation between their activation minimizes the net mediolateral patellar force. These results provide important insights into the interpretation of muscle covariations and their role in movement control.

Comparing the Effects of SUREE Programs on People With Scapular Downward Rotation Syndrome: A Randomized Clinical Trial

CONTEXT

Scapular downward rotation syndrome (SDRS) is an impaired alignment that causes shoulder and neck pain. Interventions may lead to the reduction of pain intensity and joint position error (JPE) and improved range of motion (ROM).

OBJECTIVE

To evaluate the effects of 6-week Scapular Upward Rotation and Elevation Exercises (SUREE) with and without visual feedback on pain, ROM, and JPE in people with SDRS.

STUDY DESIGN

Randomized control trial.

SETTING

Institutional practice.

PARTICIPANTS

Forty-two young and active subjects (22.61 [1.80] y; 27 males and 15 females) with unilateral SDRS randomly assigned into 3 groups (2 intervention groups and 1 control group).

INTERVENTIONS

SUREE without and with visual feedback programs.

MAIN OUTCOME MEASURES

Pain, neck-flexion and rotation ROMs, and JPE were measured using visual analog scale (score), double inclinometer method, universal goniometer method (degrees), and a dual digital inclinometer (degrees), respectively, before and after interventions.

RESULTS

The results showed statistically significant changes within the experimental groups in all variables except for the neck rotation ROM in the SUREE intervention without visual feedback (P < .05). However, there were no changes in the control group before and after the interventions in all dependent variables (P < .05). Also, there were no significant differences between both experimental groups concerning all dependent variables except for the rotation ROM (P < .05).

CONCLUSION

The results suggest that the 6-week SUREE with and without visual feedback programs result in decreased neck pain and improved flexion ROM and JPE during active neck motions in subjects with unilateral SDRS. However, the 6-week SUREE with visual feedback may improve the neck rotation ROM in subjects with unilateral SDRS. However, further studies are needed to confirm the results of this study.

Changes in Knee Vastii Muscle Activity in Women with Patellofemoral Pain Syndrome During the Menstrual Cycle

BACKGROUND

Changes in hormonal levels during the menstrual cycle are known to affect muscle electromyographic (EMG) activity, but no studies have investigated the effect of hormonal changes on the EMG activity of muscles around the knee in patients with patellofemoral pain syndrome (PFPS).

OBJECTIVE

To evaluate the EMG activity of the vastus medialis obliquus (VMO) and vastus lateralis (VL) muscles during toe rise and heel rock tasks in different phases of the menstrual cycle in women with PFPS.

DESIGN

Cross sectional study.

SETTING

Rehabilitation Research Center at the School of Rehabilitation Sciences of Shiraz University of Medical Sciences.

PARTICIPANTS

Ten women with PFPS between 18 and 40 years of age.

INTERVENTION

Not applicable.

MAIN OUTCOME MEASURES

The VL/VMO amplitude ratio and differences between onset (onset VL-onset VMO) of vastii muscle activity were measured in the affected limb during rise and rock tasks in the follicular and ovulatory phases of the menstrual cycle. The signals were analyzed with MATLAB software.

RESULTS

During both tasks, there were no significant changes in onset differences in vastii muscles between the ovulatory and follicular phases. However, the amplitude ratio (VL/VMO) was significantly lower in the ovulatory phase compared to the follicular phase (P = .035 for rise tasks and .010 for rock tasks).

CONCLUSION

The menstrual cycle may affect some EMG parameters. These factors can be taken into account when planning sports and rehabilitation training programs.

Patellofemoral cartilage stresses are most sensitive to variations in vastus medialis muscle forces

The purpose of this study was to evaluate the effects of variations in quadriceps muscle forces on patellofemoral stress. We created subject-specific finite element models for 21 individuals with chronic patellofemoral pain and 16 pain-free control subjects. We extracted three-dimensional geometries from high resolution magnetic resonance images and registered the geometries to magnetic resonance images from an upright weight bearing squat with the knees flexed at 60°. We estimated quadriceps muscle forces corresponding to 60° knee flexion during a stair climb task from motion analysis and electromyography-driven musculoskeletal modelling. We applied the quadriceps muscle forces to our finite element models and evaluated patellofemoral cartilage stress. We quantified cartilage stress using an energy-based effective stress, a scalar quantity representing the local stress intensity in the tissue. We used probabilistic methods to evaluate the effects of variations in quadriceps muscle forces from five trials of the stair climb task for each subject. Patellofemoral effective stress was most sensitive to variations in forces in the two branches of the vastus medialis muscle. Femur cartilage effective stress was most sensitive to variations in vastus medialis forces in 29/37 (78%) subjects, and patella cartilage effective stress was most sensitive to variations in vastus medialis forces in 21/37 (57%) subjects. Femur cartilage effective stress was more sensitive to variations in vastus medialis longus forces in subjects classified as maltrackers compared to normal tracking subjects (p = 0.006). This study provides new evidence of the importance of the vastus medialis muscle in the treatment of patellofemoral pain.

The effects of whole body vibration combined computerized postural control training on the lower extremity muscle activity and cerebral cortex activity in stroke patients

[Purpose] The purpose of this study was to examine the effect of computerized postural control training using whole body vibration on lower limb muscle activity and cerebral cortical activation in acute stroke patients. [Subjects and Methods] Thirty stroke patients participated and were divided into groups of 10, a group of the computerized postural control training using whole body vibration (Group I), the computerized postural control training combined with aero step (Group II) and computerized postural control training (Group III). MP100 was used to measure lower limb muscle activity, and QEEG-8 was used to measure cerebral cortical activation. [Results] Comparison of muscle activity and cerebral cortical activation before and after intervention between groups showed that Group I had significant differences in lower limb muscle activity and cerebral cortical activation compared to Groups II and III. [Conclusion] This study showed that whole body vibration combined computerized postural control training is effective for improving muscle activity and cerebral cortex activity in stroke patients.

Carryover effect of hip and knee exercises program on functional performance in individuals with patellofemoral pain syndrome

[Purpose] This study was carried out to investigate the carryover effect of hip and knee exercises program on functional performance (single legged hop test as functional performance test and Kujala score for functional activities). [Subjects and Methods] Thirty patients with patellofemoral pain syndrome were randomly assigned into two equal groups. Group (A) consisted of 15 patients undergoing hip strengthening exercises for four weeks then measuring all variables followed by additional four weeks of knee exercises program then measuring all variables again. Group (B): consisted of 15 patients undergoing knee exercises program for four weeks then measuring all variables followed by additional four weeks of hip strengthening exercises then measuring all variables. Functional abilities and knee muscles performance were assessed using Kujala questionnaire and single legged hop test respectively pre and after the completion of the first 4 weeks then after 8 weeks for both groups. [Results] Significantly increase in Kujala questionnaire in group A compared with group B was observed. While, there were significant increase in single legged hop performance test in group B compared with group A. [Conclusion] Starting with hip exercises improve the performance of subjects more than functional activities while starting with knee exercises improve the functional activities of subjects more than performance.

The effects of training using EMG biofeedback on stroke patients upper extremity functions

[Purpose] While electromyography (EMG) biofeedback has been recently used in diverse therapeutic interventions for stroke patients, research on its effects has been lacking. Most existing studies are confined to functions of the lower extremities, and research on upper extremity functional recovery using EMG biofeedback training is limited. Therefore, this study examined the effects of training using EMG biofeedback on stroke patients' upper extremity functions. [Subjects and Methods] The subjects of this study included 30 hemiplegia patients whose disease duration was longer than six months. They were randomly divided into a control group (n=15) receiving traditional rehabilitation therapy and an experimental group (n=15) receiving both traditional rehabilitation therapy and training using EMG biofeedback. The program lasted for a total of four weeks. In order to examine the subjects' functional recovery, the author measured their upper limb function using the Fugl-Meyer Assessment and Manual Function Test, and activities of daily living using the Functional Independence Measure before and after training. [Results] A comparison of the study groups revealed that those in the experimental group experienced greater improvement in upper extremity function after training in all tests compared to the control group; however, there was no significant difference in terms of the activities of daily living between the two groups. The results of this study were as follows. [Conclusion] Thus, stroke patients receiving intensive EMG biofeedback showed more significant upper extremity functional recovery than those who only received traditional rehabilitation therapy.

A study on muscle activity and ratio of the knee extensor depending on the types of squat exercise

[Purpose] For preventing the patellofemoral pain syndrome, this study aims to suggest a proper squat method, which presents selective muscle activity of Vastus Medialis Oblique and muscle activity ratios of Vastus Medialis Oblique/Vastus Lateralis by applying squat that is a representative weight bearing exercise method in various ways depending on the surface conditions and knee bending angles. [Subjects and Methods] An isometric squat that was accompanied by hip adduction, depending on the surface condition and the knee joint flexion angle, was performed by 24 healthy students. The muscle activity and the ratio of muscle activity were measured. [Results] In a comparison of muscle activity depending on the knee joint flexion angle on a weight-bearing surface, the vastus medialis oblique showed a significant difference at 15° and 60°. Meanwhile, in a comparison of the muscle activity ratio between the vastus medialis oblique and the vastus lateralis depending on the knee joint flexion angle on a weight-bearing surface, significant differences were observed at 15° and 60°. [Conclusion] An efficient squat exercise posture for preventing the patellofemoral pain syndrome is to increase the knee joint bending angle on a stable surface. But it would be efficient for patients with difficulties in bending the knee joint to keep a knee joint bending angle of 15 degrees or less on an unstable surface. It is considered that in future, diverse studies on selective Vastus Medialis Oblique strengthening exercise methods would be needed after applying them to patients with the patellofemoral pain syndrome.

Patellofemoral Pain

Patellofemoral pain is characterized by insidious onset anterior knee pain that is exaggerated under conditions of increased patellofemoral joint stress. A variety of risk factors may contribute to the development of patellofemoral pain. It is critical that the history and physical examination elucidate those risk factors specific to an individual in order to prescribe an appropriate and customized treatment plan. This article aims to review the epidemiology, risk factors, diagnosis, and management of patellofemoral pain.

The correlation between muscle activity of the quadriceps and balance and gait in stroke patients

[Purpose] The purpose of this study was to examine the correlation between quadriceps muscle activity and balance and gait in stroke patients. [Subjects and Methods] Fifty-five stroke patients (30 males 25 females; mean age 58.7 years; stroke duration 4.82 months; Korean mini-mental state examination score 26.4) participated in this study. MP100 surface electromyography, BioRescue, and LUKOtronic were used to measure the quadriceps muscle activity, balance, and gait, respectively. [Results] There was a significant correlation between quadriceps muscle activity (vastus lateralis % reference voluntary contraction, vastus medialis % reference voluntary contraction) and balance (limits of stability) and gait (gait velocity) but there was none between vastus lateralis % reference voluntary contraction, vastus medialis % reference voluntary contraction. [Conclusion] An increase in quadriceps muscle activity will improve balance and gait ability. To improve function in stroke patients, training is needed to strengthen the quadriceps muscles.

Lower extremity muscles activity in standing and sitting position with use of sEMG in patients suffering from Charcot-Marie-Tooth syndrome

There is very limited, evidenced data about movement possibilities in patients with high level of lower limb muscles atrophy and fatigue in patients suffering from Charcot-Marie-Tooth syndrome. Patient (age 46) suffering from Charcot-Marie-Tooth disease for 30 years with multiple movement restrictions and muscles atrophy above knees took part into the study. Tests were performed for 8 muscles of the lower limb and pelvis. Muscles electrical activity was tested in sitting and standing position (for knees extended and hyperextended). In the right leg rectus femoris, vastus lateralis obliquus, gluteus medius and semitendinosus muscles activated at first and were working the longest time. The highest activity was observed in standing position with knees extended. In the left leg rectus femoris and biceps femoris muscles activated at first and biceps femoris was working the longest time. Activity level in left lower limb is much lower than in the right one. Muscles weakness is asymmetric. Left leg is much weaker and engages antagonists and synergists muscles to compensate weaker rectus femoris, vastus medialis obliquus and vastus lateralis obliquus.

Rehabilitation following first-time patellar dislocation: a randomised controlled trial of purported vastus medialis obliquus muscle versus general quadriceps strengthening exercises

BACKGROUND

We aimed to define whether distal vastus medialis (VM) muscle strengthening improves functional outcomes compared to general quadriceps muscle strengthening following first-time patellar dislocation (FTPD).

METHODS

Fifty patients post-FTPD were randomised to either a general quadriceps exercise or rehabilitation programme (n=25) or a specific-VM exercise and rehabilitation regime (n=25). The primary outcome was the Lysholm knee score, and secondary outcomes included the Tegner Level of Activity score, the Norwich Patellar Instability (NPI) score, and isometric knee extension strength at various knee flexion ranges of motion. Outcomes were assessed at baseline, six weeks, six months and 12months.

RESULTS

There were statistically significant differences in functional outcome and activity levels with the Lysholm knee score and Tegner Level of Activity score at 12months in the general quadriceps exercise group compared to the VM group (p=0.05; 95% confidence interval (CI): -14.0 to 0.0/p=0.04; 95% CI: -3.0 to 0.0). This did not reach a clinically important difference. There was no statistically significant difference between the groups for the NPI score and isometric strength at any follow-up interval. The trial experienced substantial participant attrition (52% at 12months).

CONCLUSIONS

Whilst there was a statistical difference in the Lysholm knee score and Tegner Level of Activity score between general quadriceps and VM exercise groups at 12months, this may not have necessarily been clinically important. This trial highlights that participant recruitment and retention are challenges which should be considered when designing future trials in this population.

LEVEL OF EVIDENCE

Therapeutic study, Level I.

Activation of the vastus medialis oblique and vastus lateralis muscles in asymptomatic subjects during the sit-to-stand procedure

[Purpose] The purpose of this study was to examine the vastus medialis oblique to vastus lateralis ratio in two pelvic tilt positions while performing the sit-to-stand task. [Subjects and Methods] Activation of the vastus medialis oblique and the vastus lateralis muscles of 46 healthy subjects (25 males, 21 females) were recorded by surface electromyography during the STS task with anterior pelvic tilt (sit with thoracolumbar spine extended and pelvis in an anterior tilt) and neutral pelvic tilt (sit with thoracolumbar spine relaxed and pelvis in the neutral tilt position) positions. Changes in vastus medialis oblique, vastus lateralis activation and the vastus medialis oblique/vastus lateralis ratio were analyzed. [Results] Vastus medialis oblique and vastus lateralis muscle activation significantly increased in neutral pelvic tilt position, but the vastus medialis oblique/vastus lateralis ratio was not statistically different. [Conclusion] The sit-to-stand procedure with neutral pelvic tilt position increased activation of the vastus medialis oblique and vastus lateralis, usefully strengthening the quadriceps, but did not selectively activate the vastus medialis oblique muscle.

Comparison of frequency and time domain electromyography parameters in women with patellofemoral pain

BACKGROUND

Despite its high incidence, patellofemoral pain etiology remains unclear. No prior study has compared surface electromyography frequency domain parameters and surface electromyography time domain variables, which have been used as a classic analysis of patellofemoral pain.

METHODS

Thirty one women with patellofemoral pain and twenty eight pain-free women were recruited. Each participant was asked to descend a seven step staircase and data from five successful trials were collected. During the task, the vastus medialis and vastus lateralis muscle activities were monitored by surface electromyography. The data were processed and analyzed in four variables of the frequency domain (median frequency, low, medium and high frequency bands) and three time domain variables (Automatic, Cross-correlation and Visual Onset between the vastus medialis and vastus lateralis muscles). Reliability, Receiver Operating Characteristic curves and regression models were performed.

FINDINGS

The medium frequency band was the most reliable variable and different between the groups for both muscles, also demonstrated the best values of sensitivity and sensibility, 72% and 69% for the vastus medialis and 68% and 62% for the vastus lateralis, respectively. The frequency variables predicted the pain of individuals with patellofemoral pain, 26% for the vastus medialis and 20% for the vastus lateralis, being better than the time variables, which achieved only 7%.

INTERPRETATION

The frequency domain parameters presented greater reliability, diagnostic accuracy and capacity to predict pain than the time domain variables during stair descent and might be a useful tool to diagnose individuals with patellofemoral pain.

Between-muscle differences in the adaptation to experimental pain

This study aimed to determine whether muscle stress (force per unit area) can be redistributed between individual heads of the quadriceps muscle when pain is induced into one of these heads. Elastography was used to measure muscle shear elastic modulus (an index of muscle stress). Electromyography (EMG) was recorded from vastus lateralis (VL), vastus medialis (VM), and rectus femoris (RF). In experiment I ( n = 20), participants matched a knee extension force, and thus any reduction of stress within the painful muscle would require compensation by other muscles. In experiment II ( n = 13), participants matched VL EMG amplitude and were free to vary external force such that intermuscle compensation would be unnecessary to maintain the experimental task. In experiments I and II, pain was induced by injection of hypertonic saline into VM or RF. Experiment III aimed to establish whether voluntary drive to the individual muscles could be controlled independently. Participants ( n = 13) were asked to voluntarily reduce activation of VM or RF while maintaining knee extension force. During VM pain, there was no change in shear elastic modulus ( experiments I and II) or EMG amplitude of VM ( experiment II). In contrast, RF pain was associated with a reduction in RF elastic modulus ( experiments I and II: −8 to −17%) and EMG amplitude ( experiment II). Participants could voluntarily reduce EMG amplitude of RF ( −26%; P = 0.003 ) but not VM ( experiment III). These results highlight between-muscle differences in adaptation to pain that might be explained by their function (monoarticular vs. biarticular) and/or the neurophysiological constraints associated to their activation.

EFFECTS OF ADDING BIOFEEDBACK TRAINING TO ACTIVE EXERCISES AFTER TOTAL KNEE ARTHROPLASTY

The purpose of this study was to evaluate the effects of adding biofeedback training to active exercise training on quadriceps torque, voluntary activation and functional activity after total knee arthroplasty (TKA). A total of 45 patients with unilateral TKA participated in this study; their ages ranged from 58 to 67 years. They were assigned randomly to two groups. Group I comprised 21 patients who practiced an active exercise training program for 30 to 45 min/session, two sessions/week, for 4 months. Group II contained 24 patients who practiced biofeedback training in addition to the active exercise training program for 30 to 45 min/session, two sessions/week, for 4 months. Isometric peak torque of the quadriceps, voluntary activation and knee functional activity were measured. The results revealed significant improvements in quadriceps torque, voluntary activation and knee functional activity for both groups, with more improvement in knee functional activities in group II. There were nonsignificant differences between the two groups in both quadriceps peak torque and voluntary activation after training (p > 0.05). Conclusion: An active exercise program can enhance quadriceps peak torque, voluntary activation and knee functional activity after unilateral TKA. The addition of biofeedback training increases the benefits for the knee functional activity of a patient.

Diagnostic accuracy of the electromyography parameters associated with anterior knee pain in the diagnosis of patellofemoral pain syndrome

OBJECTIVE

To assess the diagnostic accuracy of the surface electromyography (sEMG) parameters associated with referred anterior knee pain in diagnosing patellofemoral pain syndrome (PFPS).

DESIGN

Sensitivity and specificity analysis.

SETTING

Physical rehabilitation center and laboratory of biomechanics and motor control.

PARTICIPANTS

Pain-free subjects (n=29) and participants with PFPS (n=22) selected by convenience.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURE

The diagnostic accuracy was calculated for sEMG parameters' reliability, precision, and ability to differentiate participants with and without PFPS. The selected sEMG parameter associated with anterior knee pain was considered as an index test and was compared with the reference standard for the diagnosis of PFPS. Intraclass correlation coefficient, SEM, independent t tests, sensitivity, specificity, negative and positive likelihood ratios, and negative and positive predictive values were used for the statistical analysis.

RESULTS

The medium-frequency band (B2) parameter was reliable (intraclass correlation coefficient=.80-.90), precise (SEM=2.71-3.87 normalized unit), and able to differentiate participants with and without PFPS (P<.05). The association of B2 with anterior knee pain showed positive diagnostic accuracy values (specificity, .87; sensitivity, .70; negative likelihood ratio, .33; positive likelihood ratio, 5.63; negative predictive value, .72; and positive predictive value, .86).

CONCLUSIONS

The results provide evidence to support the use of EMG signals (B2-frequency band of 45-96 Hz) of the vastus lateralis and vastus medialis muscles with referred anterior knee pain in the diagnosis of PFPS.

A review of the management of patellofemoral pain syndrome

OBJECTIVE

Patellofemoral pain syndrome (PFPS) is one of the most frequently diagnosed knee conditions in the primary care, orthopedic, and sports medicine settings. Although strength training and stretching programs have traditionally been the mainstay of patient treatment, there are no consensus recovery protocols for runners experiencing PFPS. The purpose of our review is to examine recent literature regarding the efficacy of various treatment modalities in the management of patients with PFPS.

METHODS

Our review included 33 articles from a PubMed literature search using the search term PFPS treatment. The search was limited to randomized controlled trials, crossover case-controlled studies, and cohort studies with ≥ 10 participants, with trial data that were published within the last 5 years.

RESULTS

Strength training and stretching exercises continue to be strongly supported by research as effective treatment options for runners with PFPS. Recent studies have confirmed that quadriceps and hip strengthening combined with stretching in a structured physiotherapy program comprise the most effective treatment for reducing knee pain symptoms and improving functionality in patients with PFPS. As previous studies have shown, therapies such as proprioceptive training, orthotics, and taping may offer benefits as adjunctive therapies but do not show a significant benefit when they are used alone in patients with PFPS. Additionally, recent research has confirmed that surgical and pharmacologic therapies are not effective for the management of patients with PFPS.

CONCLUSION

A large number of athletes are impacted by PFPS every year, particularly young runners. Sports medicine researchers have investigated many possible therapies for patients with PFPS; however, no clear guidelines have emerged regarding the management of the syndrome. Our review analyzes recent literature on PFPS and identifies specific treatment recommendations. The most effective and strongly supported treatment modality for patients with PFPS is a combined physiotherapy program, including strength training of the quadriceps and hip abductors and stretching of the quadriceps muscle group. Adjunctive therapies, including taping, biofeedback devices, and prefabricated orthotic inserts, may provide limited additive benefits in select populations. Surgery should be avoided in all patients with PFPS.

Biofeedback in rehabilitation

This paper reviews the literature relating to the biofeedback used in physical rehabilitation. The biofeedback methods used in rehabilitation are based on biomechanical measurements and measurements of the physiological systems of the body. The physiological systems of the body which can be measured to provide biofeedback are the neuromuscular system, the respiratory system and the cardiovascular system. Neuromuscular biofeedback methods include electromyography (EMG) biofeedback and real-time ultrasound imaging (RTUS) biofeedback. EMG biofeedback is the most widely investigated method of biofeedback and appears to be effective in the treatment of many musculoskeletal conditions and in post cardiovascular accident (CVA) rehabilitation. RTUS biofeedback has been demonstrated effective in the treatment of low back pain (LBP) and pelvic floor muscle dysfunction. Cardiovascular biofeedback methods have been shown to be effective in the treatment of a number of health conditions such as hypertension, heart failure, asthma, fibromyalgia and even psychological disorders however a systematic review in this field has yet to be conducted. Similarly, the number of large scale studies examining the use of respiratory biofeedback in rehabilitation is limited. Measurements of movement, postural control and force output can be made using a number of different devices and used to deliver biomechanical biofeedback. Inertial based sensing biofeedback is the most widely researched biomechanical biofeedback method, with a number of studies showing it to be effective in improving measures of balance in a number of populations. Other types of biomechanical biofeedback include force plate systems, electrogoniometry, pressure biofeedback and camera based systems however the evidence for these is limited. Biofeedback is generally delivered using visual displays, acoustic or haptic signals, however more recently virtual reality (VR) or exergaming technology have been used as biofeedback signals. VR and exergaming technology have been primarily investigated in post-CVA rehabilitation, however, more recent work has shown this type of biofeedback to be effective in improving exercise technique in musculoskeletal populations. While a number of studies in this area have been conducted, further large scale studies and reviews investigating different biofeedback applications in different clinical populations are required.

Patellar maltracking is prevalent among patellofemoral pain subjects with patella alta: an upright, weightbearing MRI study

The purpose of this study is to determine if patellar maltracking is more prevalent among patellofemoral (PF) pain subjects with patella alta compared to subjects with normal patella height. We imaged 37 PF pain and 15 pain free subjects in an open-configuration magnetic resonance imaging scanner while they stood in a weightbearing posture. We measured patella height using the Caton-Deschamps, Blackburne-Peel, Insall-Salvati, Modified Insall-Salvati, and Patellotrochlear indices, and classified the subjects into patella alta and normal patella height groups. We measured patella tilt and bisect offset from oblique-axial plane images, and classified the subjects into maltracking and normal tracking groups. Patellar maltracking was more prevalent among PF pain subjects with patella alta compared to PF pain subjects with normal patella height (two-tailed Fisher's exact test, p<0.050). Using the Caton-Deschamps index, 67% (8/12) of PF pain subjects with patella alta were maltrackers, whereas only 16% (4/25) of PF pain subjects with normal patella height were maltrackers. Patellofemoral pain subjects classified as maltrackers displayed a greater patella height compared to the pain free and PF pain subjects classified as normal trackers (two-tailed unpaired t-tests with Bonferroni correction, p<0.017). This study adds to our understanding of PF pain in two ways-(1) we demonstrate that patellar maltracking is more prevalent in PF pain subjects with patella alta compared to subjects with normal patella height; and (2) we show greater patella height in PF pain subjects compared to pain free subjects using four indices commonly used in clinics.

Evaluation of electromyographic biofeedback for the quadriceps femoris: a systematic review

OBJECTIVE

To critically review evidence for the effectiveness of electromyographic biofeedback (EMGB) of the quadriceps femoris muscle in treating various knee conditions.

DATA SOURCES

Databases used to locate randomized controlled trials included PubMed (1980-2010), Cumulative Index of Nursing and Allied Health Literature (CINAHL, 1995-2007), Web of Science (1986-2010), SPORTDiscus (1990-2007), and Physiotherapy Evidence Database (PEDro). Key words were knee and biofeedback.

STUDY SELECTION

The criteria for selection were clinical randomized controlled trials in which EMGB of the quadriceps femoris was used for various knee conditions of musculoskeletal origin. Trials were excluded because of research designs other than randomized controlled trials, articles published in a non-English language, inclusion of healthy research participants, inability to identify EMGB as the source of clinical improvement, and lack of pain, functional outcome, or quadriceps torque as outcome measures.

DATA EXTRACTION

Twenty specific data points were abstracted from each clinical trial under the broad categories of attributes of the patient and injury, treatment variables for the EMGB group, treatment variables for the control group, and attributes of the research design.

DATA SYNTHESIS

Eight trials yielded a total of 319 participants with patellofemoral pain syndrome (n = 86), anterior cruciate ligament reconstruction (n = 52), arthroscopic surgery (n = 91), or osteoarthritis (n = 90). The average methodologic score of the included studies was 4.6/10 based on PEDro criteria. Pooled analyses demonstrated heterogeneity of the included studies, rendering the interpretation of the pooled data inappropriate. The EMGB appeared to benefit short-term postsurgical pain or quadriceps strength in 3 of 4 postsurgical investigations but was ineffective for chronic knee conditions such as patellofemoral pain and osteoarthritis in all 4 studies. Because the findings are based on limited data, caution is warranted until more randomized controlled trials are conducted to support or refute the general trends observed in this report.

The influence of asymmetric quadriceps loading on patellar tracking--an in vitro study

BACKGROUND

In patients with anterior knee pain and patellar instability, a specific training of the quadriceps muscle - especially the vastus medialis - is often recommended, although the practicability is discussed controversially and the proof of a measurable clinical effect is difficult. Therefore, this in vitro study investigates the influence of asymmetric muscle loading on the motion of the human patella.

METHODS

Seven human knee specimens were tested in a specially developed knee simulator. During simulated weight-bearing knee flexion, the kinematics of tibia, femur and patella were measured using an ultrasound motion capture system. The quadriceps forces were controlled to achieve a constant ankle force over the whole flexion range which is assumed to represent almost physiological loading. Three different force distributions of the quadriceps were tested - a central, equally distributed load as well as mainly lateral and medial loads.

RESULTS

A significant influence of different quadriceps force distributions was found for patellar tilt around a proximodistal axis (up to 1.7°) and patellar rotation around an anteroposterior axis (up to 3.8°) with respect to the femur. Interestingly, the patellar mediolateral shift was influenced only marginally (<1.5mm).

CONCLUSIONS

Specific muscle training might help patients with patellofemoral pain and cartilage damage by a slight modification of the kinematics, but we could show that even highly asymmetric quadriceps loads only led to a small alteration of the mediolateral shift in case of a physiologic anatomy of the trochlear groove.

Effect of therapeutic modalities on patients with patellofemoral pain syndrome: a systematic review

Context:

Patellofemoral pain syndrome (PFPS) is a common orthopaedic condition for which operative and nonoperative treatments have been used. Therapeutic modalities have been recommended for the treatment of patients with PFPS—including cold, ultrasound, phonophoresis, iontophoresis, neuromuscular electrical stimulation, electrical stimulation for pain control, electromyographic biofeedback, and laser.

Objective:

To determine the effectiveness of therapeutic modalities for the treatment of patients with PFPS.

Data Sources:

In May and August 2010, Medline was searched using the following databases: PubMed, CINAHL, Web of Science Citation Index, Science Direct, ProQuest Nursing & Allied Health, and Your Journals@OVID.

Study Selection:

Selected studies were randomized controlled trials that used a therapeutic modality to treat patients with PFPS. The review included articles with all outcome measures relevant for the PFPS patient: knee extension and flexion strength (isokinetic and isometric), patellofemoral pain assessment during activities of daily life, functional tests (eg, squats), Kujala patellofemoral score, and electromyographic recording from knee flexors and extensors and quadriceps femoris cross-sectional areas.

Data Extraction:

Authors conducted independent quality appraisals of studies using the PEDro Scale and a system designed for analysis of studies on interventions for patellofemoral pain.

Results:

Twelve studies met criteria: 1 on the effects of cold and ultrasound together, ice alone, iontophoresis, and phonophoresis; 3, neuromuscular electrical stimulation; 4, electromyographic biofeedback; 3, electrical stimulation for control of pain; and 1, laser.

Discussion:

Most studies were of low to moderate quality. Some reported that therapeutic modalities, when combined with other treatments, may be of some benefit for pain management or other symptoms. There was no consistent evidence of any beneficial effect when a therapeutic modality was used alone. Studies did not consistently provide added benefit to conventional physical therapy in the treatment of PFPS.

Conclusions:

None of the therapeutic modalities reviewed has sound scientific justification for the treatment of PFPS when used alone.

Landing pattern modification to improve patellofemoral pain in runners: a case series

STUDY DESIGN

Case series.

BACKGROUND

Patellofemoral pain is a common overuse injury in runners. Recent findings suggest that patellofemoral pain is related to high-impact loading associated with a rearfoot strike pattern. This case series describes the potential training effects of a landing pattern modification program to manage patellofemoral pain in runners.

CASE DESCRIPTION

Three female runners with unilateral patellofemoral pain who initially presented with a rearfoot strike pattern underwent 8 sessions of landing pattern modification program using real-time audio feedback from a force sensor placed within the shoe. Ground reaction forces during running were assessed with an instrumented treadmill. Patellofemoral pain symptoms were assessed using 2 validated questionnaires. Finally, running performance was measured by self-reported best time to complete a 10-km run in the previous month. The runners were assessed before, immediately after, and 3 months following training.

OUTCOMES

The landing pattern of runners was successfully changed from a rearfoot to a nonrearfoot strike pattern after training. This new pattern was maintained 3 months after the program. The vertical impact peak and rates of loading were shown to be reduced. Likewise, the symptoms related to patellofemoral pain and associated functional limitations were improved. However, only 1 of the participants reported improved running performance after the training.

DISCUSSION

This case series provided preliminary data to support further investigation of interventions leading to landing pattern modification in runners with patellofemoral pain.

LEVEL OF EVIDENCE

Therapy, level 4.

Patellar maltracking correlates with vastus medialis activation delay in patellofemoral pain patients

BACKGROUND

Delayed onset of vastus medialis (VM) activity compared with vastus lateralis activity is a reported cause for patellofemoral pain. The delayed onset of VM activity in patellofemoral pain patients likely causes an imbalance in muscle forces and lateral maltracking of the patella; however, evidence relating VM activation delay to patellar maltracking is sparse. The aim of this study was to investigate the relationship between VM activation delay and patellar maltracking measures in pain-free controls and patellofemoral pain patients.

HYPOTHESIS

Patellar tilt and bisect offset, measures of patellar tracking, correlate with VM activation delay in patellofemoral pain patients classified as maltrackers.

STUDY DESIGN

Case control study; Level of evidence, 3.

METHODS

Vasti muscle activations were recorded in pain-free (n = 15) and patellofemoral pain (n = 40) participants during walking and jogging. All participants were scanned in an open-configuration magnetic resonance scanner in an upright weightbearing position to acquire the position of the patella with respect to the femur. Patellar tilt and bisect offset were measured, and patellofemoral pain participants were classified into normal tracking and maltracking groups.

RESULTS

Correlations between VM activation delay and patellar maltracking measures were statistically significant in only the patellofemoral pain participants classified as maltrackers with both abnormal tilt and abnormal bisect offset (R(2) = .89, P < .001, with patellar tilt during walking; R(2) = .75, P = .012, with bisect offset during jogging). There were no differences between the means of activation delays in pain-free and all patellofemoral pain participants during walking (P = .516) or jogging (P = .731).

CONCLUSION

There was a relationship between VM activation delay and patellar maltracking in the subgroup of patellofemoral pain participants classified as maltrackers with both abnormal tilt and abnormal bisect offset.

CLINICAL RELEVANCE

A clinical intervention such as VM retraining may be effective in only a subset of patellofemoral pain participants-namely, those with excessive tilt and excessive bisect offset measures. The results highlight the importance of appropriate classification of patellofemoral pain patients before selection of a clinical intervention.