Electromechanical delay of the vastus medialis obliquus and vastus lateralis in individuals with patellofemoral pain syndrome

Improvement of Pain and Function by Using Botulinum Toxin Type A Injection in Patients with an Osteoarthritic Knee with Patellar Malalignment: An Electromyographic Study

Objective: To determine the pain and electromyographic (EMG) amplitude ratio of the vastus medialis oblique (VMO) to the vastus lateralis (VL) after botulinum toxin type A (BTA) was injected in the bilateral osteoarthritic knee of patients with patellar malalignment for analysis. Material and methods: A total of fifteen patients were recruited; the more symptomatic knee of each patient received a BTA injection (BTA side). The other set of patients were left untreated. In all, fifteen healthy participants comprised the control group. The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and numeric rating scale (NRS) for pain were assessed. The EMG amplitude of VL and VMO activity was recorded using an isokinetic dynamometer and synchronized using the BIOPAC MP100. The data were collected before and at 4, 8, and 12 weeks post−BTA injection. Results: The EMG ratios of the patient group were lower than those of the control group at all testing velocities (p < 0.05). The VMO/VL ratio improved significantly on the BTA side only. The VMO/VL ratios on the BTA side were higher than those on the untreated side (p < 0.05). Knee pain decreased significantly after the BTA injection. The EMG ratios were negatively correlated with the NRS and WOMAC scores. Conclusion: BTA injection effectively reduces knee pain and restores the EMG ratio between the VMO and VL.

Local neuromuscular characteristics associated with patellofemoral pain: A systematic review and meta-analysis

BACKGROUND

Local neuromuscular deficits have been reported in people with patellofemoral pain. We synthesised the neuromuscular characteristics associated with patellofemoral pain to help identify interventional targets and potential mechanisms.

METHODS

Five databases were searched for local neuromuscular characteristics in case-control studies. Electromyography, flexibility, muscle performance and cross-sectional area data were derived from functional or isolated task investigations and synthesised accordingly. An evidence gap map was constructed.

FINDINGS

Sixty-seven studies were included. In functional tasks, electromyographic investigations showed moderate evidence of small effect for vastus medialis onset-delays relative to vastus lateralis (0.44 [0.03, 0.85]) during stepping/stair negotiation tasks, and higher biceps femoris mean excitation amplitudes (0.55 [0.06, 1.04]) in single-leg triple-hop test. In isolated tasks, we found moderate evidence of medium effect for lower Hoffman-reflex amplitude of vastus medialis (-1.12 [-1.56, -0.67]). Muscle performance investigations showed; strong evidence with medium and small effects for lower extensors concentric (-0.61 [-0.81, -0.40]) and eccentric (-0.56 [-0.79, -0.33]) strength, and moderate evidence of medium effect of lower isometric (-0.64 [-0.87, -0.41]) strength, moderate evidence with small effect for rate of force development to 30% (-0.55[-0.89, -0.21]), 60% (-0.57[-0.90, -0.25]) and medium effect to 90% (-0.76[-1.43, -0.10]) of maximum voluntary contraction, and small effect for lower flexors concentric strength (-0.46 [-0.74, -0.19]) and extensors total work (-0.48 [-0.90, -0.07]). Flexibility investigations showed tighter hamstrings (-0.57 [-0.99, -0.14]).

INTERPRETATION

Differences within quadriceps and hamstrings motor-control, hamstrings tightness, and quadriceps and hamstrings weakness are associated with patellofemoral pain, and can be used to guide investigations of treatment effects.

Botulinum toxin injections as salvage therapy is beneficial for management of patellofemoral pain syndrome

Purpose

Patellofemoral pain syndrome (PFPS) is a common pathology usually presenting with anterior or retropatellar pain. It is associated with a relative imbalance between the vastus medialis oblique (VMO) and the vastus lateralis (VL) muscles. This can lead to considerable morbidity and reduced quality of life (QOL). This study aims to assess the long-term functional outcome of PFPS treated with VL muscle botulinum toxin A (BoNT-A) injection.

Materials and methods

A retrospective review was performed on 26 consecutive patients (31 knees) with a mean age of 50.1 years (± 19.7 years) who were treated with BoNT-A injections to the VL muscle followed by physiotherapy between 2008 and 2015. Pre- and post-treatment pain levels (numerical rating scale, NRS), QOL (SF-6D), and functional scores (Kujala and Lysholm questionnaires) were measured. Demographics, physical therapy compliance, previous surgeries, perioperative complications, and patient satisfaction levels were collected.

Results

The mean follow-up time was 58.8 ± 36.4 months. There were significant improvements in all the examined domains. The average pain score (NRS) decreased from 7.6 to 3.2 (P < 0.01), and the Kujala, Lysholm, and SF-6D scores improved from 58.9 to 82.7 (P < 0.001), 56.2 to 83.2 (P < 0.001), and 0.6 to 0.8 (P < 0.001), respectively. Similar delta improvement was achieved irrespective of gender, age, compliance to post-treatment physical therapy, or coexisting osteoarthritis. Patients who presented with a worse pre-treatment clinical status achieved greater improvement. Prior to BoNT-A intervention, 16 patients (18 knees) were scheduled for surgery, of whom 12 (75%, 13 knees) did not require further surgical intervention at the last follow-up.

Conclusions

A single intervention of BoNT-A injections to the VL muscle combined with physiotherapy is beneficial for the treatment of patients with persistent PFPS.

Level III evidence

Retrospective cohort study.

Association Between Neuromuscular Variables and Graft Harvest in Soft Tissue Quadriceps Tendon Versus Bone-Patellar Tendon-Bone Anterior Cruciate Ligament Autografts

Background:

Quadriceps tendon (QT) autografts are increasingly popular for anterior cruciate ligament reconstruction (ACLR). However, no study has compared QT autografts with bone–patellar tendon–bone (BTB) autografts regarding the electromechanical delay (EMD), the peak torque (PT), and the rate of force development (RFD) in the superficial quadriceps muscles (rectus femoris [RF], vastus medialis [VM], and vastus lateralis [VL]).

Hypotheses:

We hypothesized (1) there would be a significantly lower PT, lower RFD, and longer quadriceps EMD of the operative limb for the QT versus the BTB autograft; (2) the PT, the RFD, and the quadriceps EMD of the operative limb would be significantly depressed compared with those of the nonoperative limb, regardless of the surgical technique; and (3) there would be greater increases in the RF EMD than in the VM or the VL EMD.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

A total of 34 patients (age, 18-40 years), who had undergone ACLR (QT, n = 17; BTB, n = 17) at least 1 year before testing and performed 3 perceived maximal effort isometric tests, which were time synchronized with surface electromyography (EMG) on their operative and nonoperative limbs, were included in this study. EMD, PT, and RFD data were analyzed using a 2 (limb) × 2 (graft) × 3 (repetition) mixed repeated-measures analysis of variance.

Results:

The EMD, the PT, and the RFD were not significantly affected by graft choice. For the VL, a significant repetition × graft × limb interaction was detected for the VL EMD (P = .027; ηp = 0.075), with repetition 3 having longer EMD than repetition 2 (mean difference [MD], 16 milliseconds; P = .039). For the RF EMD, there was a significant repetition × limb interaction (P = .027; ηp = 0.074), with repetition 3 being significantly longer on the operative versus the nonoperative limb (MD, 24 milliseconds; P = .004). Further, the operative limb EMD was significantly longer for repetition 3 versus repetition 2 (MD, 17 milliseconds; P = .042). For the PT, there was a significant effect for repetition (P = .003; ηp = 0.114), with repetition 1 being significantly higher than both repetitions 2 (MD, 8.52 N·m; P = .001) and 3 (MD, 7.79 N·m; P = .031). For the RFD, significant limb (P = .034; ηp = 0.092) and repetition (P = .010; ηp = 0.093) effects were seen, with the nonoperative limb being significantly faster than the operative limb (MD, 23.7 N·m/s; P = .034) and repetition 1 being significantly slower than repetitions 2 (MD, -20.46 N·m/s; P = .039) or 3 (MD, −29.85 N·m/s; P = .002).

Conclusion:

The EMD, the PT, and the RFD were not significantly affected by graft type when comparing QT and BTB autografts for ACLR; however, all neuromuscular variables were affected regardless of the QT or the BTB harvest.

Effects of whole-body vibration plus hip-knee muscle strengthening training on adult patellofemoral pain syndrome: a randomized controlled trial

PURPOSE

To investigate whether whole-body vibration (WBV) plus hip-knee muscle strengthening is more efficient in relieving pain and improving function than hip-knee strengthening alone.

METHODS

Thirty-six participants with patellofemoral pain syndrome (PFPS) were recruited and randomly allocated to either the (1) hip-knee strengthening only (HK group, n = 18) or (2) WBV plus hip-knee strengthening group (WHK group, n = 18). All participants attended 18 physiotherapy sessions (3 sessions/week, 40 min/session) over 6 weeks. Data on symptoms, function, surface electromyography (sEMG) signals from the vastus medialis and gluteus medius, and quality of life were evaluated at baseline (T₀), 6 weeks after (T₆), and the 12-week follow-up (T₁₈).

RESULTS

Significant group × time interactions were found for the VAS score (p < 0.001) and vastus medialis performance (p ≤ 0.015). The WHK group exhibited a greater pain relief than did the HK group at T₁₈ (p ≤ 0.014). The WHK group exhibited significantly larger improvements in the RMS value than did the HK group at T₆ (p ≤ 0.011).

CONCLUSIONS

The present study shows that 6 weeks of WBV plus hip-knee strengthening can improve vastus medialis performance and maintain long-term pain relief to a significantly greater extent than can hip-knee strengthening alone.IMPLICATIONS FOR REHABILITATIONThe present study shows that 6 weeks of WBV plus hip-knee strengthening can improve vastus medialis performance and maintain long-term pain relief to a significantly greater extent than can hip-knee strengthening alone.

The use of yank-time signal as an alternative to identify kinematic events and define phases in human countermovement jumping

Detailed examinations of both the movement and muscle activation patterns used by animals and humans to complete complex tasks are difficult to obtain in many environments. Therefore, the ability to infer movement and muscle activation patterns after capture of a single set of easily obtained data is highly sought after. One possible solution to this problem is to capture force-time data through the use of appropriate transducers, then interrogate the signal's derivative, the yank-time signal, which amplifies, and thus highlights, temporal force-time changes. Because the countermovement vertical jump (CMJ) is a complex movement that has been well studied in humans, it provides an excellent preliminary model to test the validity of this solution. The aim of the present study was therefore to explore the use of yank-time signal, derived from vertical ground reaction force-time data, to identify and describe important kinematic (captured using three-dimensional motion analysis) and kinetic events in the CMJ, and to relate these to possible muscle activation (electromyography) events that underpin them. It was found that the yank-time signal could be used to accurately identify several key events during the CMJ that are likely to be missed or misidentified when only force-time data are inspected, including the first instances of joint flexion and centre of mass movement. Four different jump profiles (i.e. kinematic patterns) were inferred from the yank-time data, which were linked to different patterns of muscle activation. Therefore, yank-time signal interrogation provides a viable method of estimating kinematic patterns and muscle activation strategies in complex human movements.

The effects of a standard elliptical vs. a modified elliptical with a converging footpath on lower limb kinematics and muscle activity

Elliptical trainers that increase the inter-pedal distance may have potential benefits for knee osteoarthritis by decreasing the amount of knee varus. Modifying elliptical trainers with a converging footpath and reduced inter-pedal distance may be beneficial for reducing anterior knee pathology risk by decreasing knee valgus angles. Twenty-one college students participated in a single testing session. Participants exercised on two different elliptical trainers, one modified with a converging footpath and reduced inter-pedal width, and a standard elliptical trainer. Participants exercised for 2 min at three ramps incline at 120 strides per minute and constant work rate. Three-dimensional kinematics and electromyography of the dominant lower limb were recorded. Multiple 2 × 3 (Elliptical x Incline) ANOVAs with Bonferroni corrections were used to compare the two elliptical trainers at each incline for kinematics and muscle activity. The modified elliptical trainer displayed significantly decreased peak knee valgus (p = 0.031, η p 2 = 0.234 ), peak knee flexion (p = 0.006, η p 2 = 0.246 ), and interactions for peak knee flexion (p = 0.001, η p 2 = 0.250 ) and vastus lateralis (p < 0.01, η p 2 = 0.380 ) muscle activity compared to the standard elliptical trainer. The decreased peak knee valgus and flexion angles could be beneficial for reducing long-term injury risk for anterior knee pathologies.

Fatigue in complete spinal cord injury and implications on total delay

The use of neuromuscular electrical stimulation (NMES) to artificially restore movement in people with complete spinal cord injury (SCI) induces an accelerated process of muscle fatigue. Fatigue increases the time between the beginning of NMES and the onset of muscle force (Delay_TOT ). Understanding how much muscle fatigue affects the Delay_TOT in people with SCI could help in the design of closed-loop neuroprostheses that compensate for this delay, thus making the control system more stable. The aim of this study was to evaluate the impact of the extent of fatigue on Delay_TOT and peak force of the lower limbs in people with complete SCI. Fifteen men-young adults with complete SCI (paraplegia and tetraplegia) and stable health-participated in the experiment. Delay_TOT was defined as the time interval between the beginning of NMES application until the onset of muscle force. The electrical intensity of NMES applied was adjusted individually and consisted of the amplitude required to obtain a full extension of the knee (0°), considering the maximum electrically stimulated extension (MESE). Subsequently, 70% of the MESE was applied during the fatigue induction protocol. Significant differences were identified between the moments before and after the fatigue protocol, both for peak force (P ≤ .026) and Delay_TOT (P ≤ .001). The medians and interquartile range of the Delay_TOT were higher in postfatigue (199.0 ms) when compared to the moment before fatigue (146.5 ms). The medians and interquartile range of the peak force were higher in unfatigued lower limbs (0.43 kgf) when compared to the moment postfatigue (0.27 kgf). The results support the hypothesis that muscle fatigue influences the increase in Delay_TOT and decrease in force production in people with SCI. For future applications, the combined evaluation of the delay and force in SCI patients provides valuable feedback for NMES paradigms. The study will provide potentially critical muscle mechanical evidence for the investigation of the evolution of atrophy.

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.

Effects of kinesio taping on neuromuscular performance and pain of individuals affected by patellofemoral pain: A randomized controlled trial

Patellofemoral pain (PFP) is one of the most frequent musculoskeletal dysfunctions in the knee and its treatment is controversial. This study analyzed the effects of Kinesio Taping (KT) immediately and 72 hours after its application on the electromyographic (EMG) activity of the vastus medialis oblique (VMO) muscle, on the isokinetic performance of the quadriceps femoris and on the pain of subjects with PFP. Fifty-four participants were divided into three groups and performed one of the following protocols: (1) control group (CG)-remained at rest; (2) KT tension group (TG)-KT application with tension in the VMO region; and (3) KT without tension group (WTG)-KT application without tension in the same region. VMO and vastus lateralis (VL) EMG activity (RMS and onset), isokinetic performance and pain intensity were evaluated at three moments: before KT application, immediately after and 72 hours after. A mixed model ANOVA was used for statistical analysis with a significance level of 5% (p ≤ 0.05). No differences between the evaluated groups were found in relation to EMG variables and isokinetic performance. A reduction in pain intensity was found in the WTG in comparison to CG, after 72 hours. KT does not alter EMG parameters nor the isokinetic performance of subjects with PFP. However, we noticed reduced pain in the group submitted to the technique without tension 72 hours after its application.

A wavelet based time frequency analysis of electromyograms to group steps of runners into clusters that contain similar muscle activation patterns

PURPOSE

To wavelet transform the electromyograms of the vastii muscles and generate wavelet intensity patterns (WIP) of runners. Test the hypotheses: 1) The WIP of the vastus medialis (VM) and vastus lateralis (VL) of one step are more similar than the WIPs of these two muscles, offset by one step. 2) The WIPs within one muscle differ by having maximal intensities in specific frequency bands and these intensities are not always occurring at the same time after heel strike. 3) The WIPs that were recorded form one muscle for all steps while running can be grouped into clusters with similar WIPs. It is expected that clusters might have distinctly different, cluster specific mean WIPs.

METHODS

The EMG of the vastii muscles from at least 1000 steps from twelve runners were recorded using a bipolar current amplifier and yielded WIPs. Based on the weights obtained after a principal component analysis the dissimilarities (1-correlation) between the WIPs were computed. The dissimilarities were submitted to a hierarchical cluster analysis to search for groups of steps with similar WIPs. The clusters formed by random surrogate WIPs were used to determine whether the groups were likely to be created in a non-random manner.

RESULTS

The steps were grouped in clusters showing similar WIPs. The grouping was based on the frequency bands and their timing showing that they represented defining parts of the WIPs. The correlations between the WIPs of the vastii muscles that were recorded during the same step were higher than the correlations of WPIs that were recorded during consecutive steps, indicating the non-randomness of the WIPs.

CONCLUSIONS

The spectral power of EMGs while running varies during the stance phase in time and frequency, therefore a time averaged power spectrum cannot reflect the timing of events that occur while running. It seems likely that there might be a set of predefined patterns that are used upon demand to stabilize the movement.

Quadriceps muscles activity during gait: comparison between PFPS subjects and healthy control

PURPOSE

The purpose of the study was to evaluate if during a common activity as walking, altered quadriceps muscular activity may be present in patellofemoral pain syndrome (PFPS) patients.

METHODS

Forty subjects with clinically diagnosed PFPS and forty healthy males matching in age, weight, height and level of sport activity were enrolled in the study. Subjects were asked to walk on an instrumented walking path at their self-selected speed. Force platform and motion tracking system were used for the analysis of the gait. Wireless surface EMG probes were used to evaluate quadriceps muscles activity. Rectus femoris, vastus medialis and lateralis activity percentage, onset and offset time, walking speed, cadence, step length, stride length, knee ROM during gait were measured and reported. Tegner activity questionnaire was reported.

RESULTS

Patient group showed a significant increasing in all quadriceps muscles activity when compared to the control (p < 0.05). In particular, for VM and VL muscle onset time was anticipated and offset time was postponed in PFPS group when compared with healthy group (p < 0.05). Knee range of motion during walking was significantly decreased in the patient group.

CONCLUSIONS

Young athletes with PFPS showed increased length of quadriceps muscles activity and reduced functional knee Rom while walking, comparing with healthy subjects, in particular muscular onset was anticipated in respect of the loading response event of the gait. Nonetheless, walking parameters were not affected by these alterations.

Patellofemoral pain in athletes

Patellofemoral pain (PFP) is a frequent cause of anterior knee pain in athletes, which affects patients with and without structural patellofemoral joint (PFJ) damage. Most younger patients do not have any structural changes to the PFJ, such as an increased Q angle and a cartilage damage. This clinical entity is known as patellofemoral pain syndrome (PFPS). Older patients usually present with signs of patellofemoral osteoarthritis (PFOA). A key factor in PFPS development is dynamic valgus of the lower extremity, which leads to lateral patellar maltracking. Causes of dynamic valgus include weak hip muscles and rearfoot eversion with pes pronatus valgus. These factors can also be observed in patients with PFOA. The available evidence suggests that patients with PFP are best managed with a tailored, multimodal, nonoperative treatment program that includes short-term pain relief with nonsteroidal anti-inflammatory drugs (NSAIDs), passive correction of patellar maltracking with medially directed tape or braces, correction of the dynamic valgus with exercise programs that target the muscles of the lower extremity, hip, and trunk, and the use of foot orthoses in patients with additional foot abnormalities.

The relationship between quadriceps strength and joint position sense, functional outcome and painful activities in patellofemoral pain syndrome

PURPOSE

The aim of this study was to investigate how strongly the concentric and eccentric quadriceps strengths were correlated with the joint position sense, functional outcomes and painful activities in patients with patellofemoral pain syndrome (PFPS).

METHODS

The study included forty-six women diagnosed with unilateral PFPS. Eccentric and concentric quadriceps strengths were recorded at 60 and 180°/s. Active knee joint position sense (JPS) was measured at 20° and 60° of flexion. Functional levels were determined by using Kujala patellofemoral scores. Pain levels during stair descending and ascending, squatting and prolonged sitting were measured using 0-10 cm visual analogue scale. The relationship of isokinetic quadriceps strength with JPS results, Kujala score and pain levels were evaluated using Spearman's correlation coefficient test.

RESULTS

Eccentric and concentric quadriceps strengths were significantly lower on involved side than uninvolved side. JPS results were poorer on the painful knee when compared to uninvolved side. While eccentric strength correlated with both JPS target angles, concentric strength was correlated only with 20°. Both eccentric and concentric strengths were significantly correlated with Kujala scores and pain levels.

CONCLUSION

Quadriceps eccentric strength was correlated more to joint position sense than concentric strength. Both eccentric and concentric quadriceps strength related to pain and functional level in PFPS patients.

Analysis of vastus lateralis and vastus medialis oblique muscle activation during squat exercise with and without a variety of tools in normal adults

[Purpose] The present study investigated the effects of squat exercises with and without a variety of tools including a gym ball, wedge, and elastic band on the vastus lateralis and vastus medialis oblique muscles. [Subjects and Methods] A total of twenty healthy subjects with no history of neurological, musculoskeletal injury, or pain in the lower extremities were recruited. All subjects performed four types of exercise (conventional squat exercise, squat exercise with a gym ball, squat exercise with a wedge, squat exercise with an elastic band). [Results] There were no significant differences between exercises in comparison of the vastus lateralis muscle activity. In the squat exercise with a wedge, significantly higher activity of the vastus medialis oblique muscle was found compared with in the squat exercise with an elastic band. [Conclusion] The present study suggests that the conventional squat exercise can be one of the useful interventions for patients with patellofemoral pain syndrome.

Which patellofemoral joint imaging features are associated with patellofemoral pain? Systematic review and meta-analysis

OBJECTIVES

To review the association between patellofemoral joint (PFJ) imaging features and patellofemoral pain (PFP).

DESIGN

A systematic review of the literature from AMED, CiNAHL, Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, PEDro, EMBASE and SPORTDiscus was undertaken from their inception to September 2014. Studies were eligible if they used magnetic resonance imaging (MRI), computed tomography (CT), ultrasound (US) or X-ray (XR) to compare PFJ features between a PFP group and an asymptomatic control group in people <45 years of age. A pooled meta-analysis was conducted and data was interpreted using a best evidence synthesis.

RESULTS

Forty studies (all moderate to high quality) describing 1043 people with PFP and 839 controls were included. Two features were deemed to have a large standardised mean difference (SMD) based on meta-analysis: an increased MRI bisect offset at 0° knee flexion under load (0.99; 95% CI: 0.49, 1.49) and an increased CT congruence angle at 15° knee flexion, both under load (1.40 95% CI: 0.04, 2.76) and without load (1.24; 95% CI: 0.37, 2.12). A medium SMD was identified for MRI patella tilt and patellofemoral contact area. Limited evidence was found to support the association of other imaging features with PFP. A sensitivity analysis showed an increase in the SMD for patella bisect offset at 0° knee flexion (1.91; 95% CI: 1.31, 2.52) and patella tilt at 0° knee flexion (0.99; 95% CI: 0.47, 1.52) under full weight bearing.

CONCLUSION

Certain PFJ imaging features were associated with PFP. Future interventional strategies may be targeted at these features.

PROSPERO REGISTRATION NUMBER

CRD 42014009503.

The Role of Botulinum Toxin Type A in the Clinical Management of Refractory Anterior Knee Pain

Anterior knee pain is a highly prevalent condition affecting largely young to middle aged adults. Symptoms can recur in more than two thirds of cases, often resulting in activity limitation and reduced participation in employment and recreational pursuits. Persistent anterior knee pain is difficult to treat and many individuals eventually consider a surgical intervention. Evidence for long term benefit of most conservative treatments or surgical approaches is currently lacking. Injection of Botulinum toxin type A to the distal region of vastus lateralis muscle causes a short term functional “denervation” which moderates the influence of vastus lateralis muscle on the knee extensor mechanism and increases the relative contribution of the vastus medialis muscle. Initial data suggest that, compared with other interventions for anterior knee pain, Botulinum toxin type A injection, in combination with an active exercise programme, can lead to sustained relief of symptoms, reduced health care utilisation and increased activity participation. The procedure is less invasive than surgical intervention, relatively easy to perform, and is time- and cost-effective. Further studies, including larger randomized placebo-controlled trials, are required to confirm the effectiveness of Botulinum toxin type A injection for anterior knee pain and to elaborate the possible mechanisms underpinning pain and symptom relief.

Muscle force cannot be directly inferred from muscle activation: illustrated by the proposed imbalance of force between the vastus medialis and vastus lateralis in people with patellofemoral pain

Muscle force cannot be directly inferred from neural drive assessed using electromyography (EMG). Although the limitations associated with inferring force from EMG are well known, this has received little attention in the clinical literature. This commentary discusses these limitations within the context of the imbalance of force production between the vastus medialis (VM) and vastus lateralis (VL) muscles, which has been speculated to contribute to the development and/or persistence of patellofemoral pain. The balance of neural drive between vasti muscles is most frequently measured with 2 approaches: (1) the onset of VM EMG relative to that of the VL, and (2) the ratio of the EMG signal amplitude of the VM and VL. Here, we demonstrate that this classical approach cannot determine whether an imbalance of force exists between the VM and VL. Considerations such as altered electromechanical delay (time between the onsets of muscle activation and patellar motion) in people with patellofemoral pain may lead to a reconsideration of the classical interpretation of the onset of VM EMG signal relative to that of the VL. Also, beyond the amplitude of the neural drive, muscle force depends on several biomechanical factors (eg, specific tension and physiological cross-sectional area). Therefore, the VL/VM activation ratio does not provide information about the VL/VM force ratio, which is ultimately the most important information from a clinical perspective. Although the literature includes defenses for both the existence and absence of this force imbalance in people with patellofemoral pain, a reconsideration of the methods used to assess this imbalance is needed.

Anterior knee pain caused by patellofemoral pain syndrome can be relieved by Botulinum toxin type A injection

OBJECTIVE

To investigate the therapeutic effects of Botulinum toxin type A (BTA) for anterior knee pain caused by patellofemoral pain syndrome (PFPS).

DESIGN

Prospective case control study for intervention.

SETTING

A tertiary hospital rehabilitation center.

PARTICIPANTS

Twelve bilateral PFPS patients with anterior knee pain were recruited. The worse pain knee was selected for injection, and the counterpart was left untreated.

INTERVENTION

Injection of BTA to vastus lateralis (VL) muscle.

MAIN OUTCOME MEASURES

Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) was used to assess pain, stiffness, and functional status of the knee, and CYBEX isokinetic dynamometer to assess isokinetic muscle force before and after BTA application to VL.

RESULTS

Remarkable improvement after receiving BTA injection was obtained not only in the questionnaire of WOMAC (p<0.05), but also in knee flexion torque (p<0.05). No significant change of knee extension torque was noted (p=0.682).

CONCLUSION

BTA injection is a good alternative treatment to improve anterior knee pain, knee function and isokinetic flexion torque.

Detection of the electromechanical delay and its components during voluntary isometric contraction of the quadriceps femoris muscle

Electromechanical delay (EMD) was described as a time elapsed between first trigger and force output. Various results have been reported based on the measurement method with observed inconsistent results when the trigger is elicited by voluntary contraction. However, mechanomyographic (MMG) sensor placed far away on the skin from the contracting muscle was used to detect muscle fiber motion and excitation-contraction (EC) coupling which may give unreliable results. On this basis, the purpose of this study was to detect EMD during active muscle contraction whilst introducing an ultrafast ultrasound (US) method to detect muscle fiber motion from a certain depth of the muscle. Time delays between onsets of EMG-MMG, EMG-US, MMG-FORCE, US-FORCE, and EMG-FORCE were calculated as 20.5 ± 4.73, 28.63 ± 6.31, 19.21 ± 6.79, 30.52 ± 8.85, and 49.73 ± 6.99 ms, respectively. Intrarater correlation coefficient (ICC) was higher than MMG when ultrafast US was used for detecton of the Δt EMG-US and Δt US-FORCE, ICC values of 0.75 and 0.70, respectively. Synchronization of the ultrafast ultrasound with EMG and FORCE sensors can reveal reliable and clinically useful results related to the EMD and its components when muscle is voluntarily contracted. With ultrafast US, we detect onset from the certain depth of the muscle excluding the tissues above the muscle acting as a low-pass filter which can lead to inaccurate time detection about the onset of the contracting muscle fibers. With this non-invasive technique, understanding of the muscle dynamics can be facilitated.

The Patella Pro study - effect of a knee brace on patellofemoral pain syndrome: design of a randomized clinical trial (DRKS-ID:DRKS00003291)

BACKGROUND

Patellofemoral pain syndrome (PFPS) is a frequent cause of anterior knee pain predominantly affecting young female patients who do not have significant chondral damage. Development of PFPS is probably multifactorial, involving various knee, hip, and foot kinematic factors. Biomechanical studies have described patellar maltracking and dynamic valgus (functional malalignment) in patients with patellofemoral pain syndrome. The literature provides evidence for short-term use of nonsteroidal anti-inflammatory drugs; short-term medially directed taping; and exercise programs focusing on the lower extremity, hip, and trunk muscles. Evidence supporting the use of patellar braces is limited because previous studies have been low quality. The aim of this article is to publish the design of a prospective randomized trial that examines the outcomes of patients with PFPS after treatment with a new patellar brace (Patella Pro) that applies medially directed force on the patella.

METHODS/DESIGN

For this multicenter trial, 156 patients (adolescents and young adults) with PFPS were recruited from orthopedic practices and orthopedic hospitals and randomly allocated to 3 months of supervised physiotherapy in combination with the Patella Pro brace or supervised physiotherapy alone. The primary outcome measures are pain (numerical analog scale); knee function (Kujala score and Knee Injury and Osteoarthritis Outcome Score); and self-reported perception of recovery at baseline, 6 weeks, 3 months, and 1 year.

DISCUSSION

Only limited evidence for the use of a patellar brace for the treatment of PFPS exists in the literature. Disputable evidence for the use of orthoses for PFPS patients has been presented in one meta-analysis, in which only one of three studies found the effect of a medially directed patellar brace to be significant. Because of these low-quality studies, the authors concluded that this evidence should be regarded as limited, and we feel there is a need for further well-designed studies to evaluate the effect of patellar bracing on PFPS-related pain. The Patella Pro study is a prospective randomized trial in which supervised physiotherapy in combination with a patellar brace is compared with supervised physiotherapy alone. This trial started in April 2012 and finished in October 2013.

TRIAL REGISTRATION

DRKS-ID:DRKS00003291, January 3rd, 2012.

Patellofemoral pain syndrome

The patellofemoral pain syndrome (PFPS) is a possible cause for anterior knee pain, which predominantly affects young female patients without any structural changes such as increased Q-angle or significant chondral damage. This literature review has shown that PFPS development is probably multifactorial with various functional disorders of the lower extremity. Biomechanical studies described patellar maltracking and dynamic valgus in PFPS patients (functional malalignment). Causes for the dynamic valgus may be decreased strength of the hip abductors or abnormal rear-foot eversion with pes pronatus valgus. PFPS is further associated with vastus medialis/vastus lateralis dysbalance, hamstring tightness or iliotibial tract tightness. The literature provides evidence for a multimodal non-operative therapy concept with short-term use of NSAIDs, short-term use of a medially directed tape and exercise programmes with the inclusion of the lower extremity, and hip and trunk muscles. There is also evidence for the use of patellar braces and foot orthosis. A randomized controlled trial has shown that arthroscopy is not the treatment of choice for treatment of PFPS without any structural changes. Patients with anterior knee pain have to be examined carefully with regard to functional causes for a PFPS. The treatment of PFPS patients is non-operative and should address the functional causes.

LEVEL OF EVIDENCE

V.