Altered vastii recruitment when people with patellofemoral pain syndrome complete a postural task

Effects of neuromuscular electrical stimulation on patellofemoral pain: A randomized controlled trial

INTRODUCTION

Patellofemoral Pain (PFP) is a common dysfunction that can compromise the performance of daily activities. Neuromuscular electrical stimulation (NMES) has been proposed as a complementary tool in the therapeutic approach.

OBJECTIVE

To analyze the effects of adding NMES to therapeutic exercises in women with PFP.

METHODS

Randomized controlled trial involving 34 women with PFP (mean age 23.8 ± 4.1), randomly assigned to two groups: exercises combined with NMES (ESG) and exercises only (ExG). The ExG followed an exercise protocol, while the ESG performed the same exercises combined with NMES. Interventions were performed twice a week for eight weeks. Primary outcome measures included pain and functional disability, while secondary outcomes encompassed electromyographic activity of the quadriceps and hip abductors, along with isokinetic performance. Assessments were performed before the intervention, after 4 and 8 weeks from the start of the protocol and 8 weeks after the conclusion of the treatment.

RESULTS

We did not observe difference between the groups in any of the analyzed variables. Both groups showed a reduction in pain and an improvement in functional disability during intragroup comparisons.

CONCLUSION

A reduction in pain and an improvement in functional disability were observed; however, there was no additional effect of NMES.

TRIAL REGISTRATION

NCT03918863.

Effects of McConnell and Kinesio taping on kinematic variables during stair descent in patients with patellofemoral pain syndrome

BACKGROUND

Studies regarding effects of therapeutic tapings when patients with patellofemoral pain syndrome (PFPS) descend stairs are limited.

OBJECTIVE

The purpose of this study was to investigate the effect of McConnell taping (MT) and Kinesio taping (KT) on kinematic variables when patients with PFPS descend stairs.

METHODS

Fifty PFPS patients were randomly assigned to either the MT group or the KT group. Pain and lower extremities joint angles were measured while descending stairs before and after the intervention. All outcomes measured were analyzed using either paired t tests or independent t tests to compare the difference within or between groups, respectively.

RESULTS

There was a statistically significant difference in both groups in anterior knee pain scale score (p< 0.05). As a result of analysis of lower extremities joint angles at initial contact, loading response, and terminal stance, there were statistically significant within-group differences in hip, knee flexion, abduction and lateral rotation angles in both groups (p< 0.05). There were statistically significant within-group differences in hip flexion, knee flexion, and dorsiflexion angles in pre-swing (p< 0.05). There was a statistically significant difference between the groups in the following events: (1) knee lateral rotation angle at initial contact; (2) hip flexion angle at loading response; (3) and hip flexion at terminal stance angle (p< 0.05).

CONCLUSION

MT and KT were effective in lowering knee pain and improving lower extremities joint angle when patients with PFPS descend stairs. In the comparison between the groups, the MT group showed significantly reduced anterior knee pain and increased range of motion of the lower extremities joint compared to the KT group.

Neurophysiology of movement inhibition during full body reaching

Our current understanding of response inhibition comes from go/no-go studies that draw conclusions based on the overt movement of single limbs (i.e., a single finger pushing a button). In general, go/no-go paradigms have found that an individual's ability to correctly inhibit the motor system is indicative of a healthy central nervous system. However, measuring inhibition by an overt behavioral response may lack the sensitivity to conclude whether the motor system is completely inhibited. Therefore, our goal was to use behavioral and neurophysiological measures to investigate inhibition of the motor system during a full-body reaching task. When directly comparing neurophysiological and behavioral measures, we found that neurophysiological measures were associated with a greater number of errors during no-go trials and faster onset times during go trials. Further analyses revealed a negative correlation between errors and onset times, such that the muscles that activated the earliest during go trials also had the greatest number of errors during no-go trials. Together, our observations show that the absence of an overt behavioral response does not always translate to total inhibition of the motor system.

Effects of McConnell and Kinesio Tapings on Pain and Gait Parameters during Stair Ambulation in Patients with Patellofemoral Pain Syndrome

Background and Objectives: The purpose of this study was to investigate the effects of McConnell and Kinesio tapings on knee pain and gait parameters during stair ambulation in patients with patellofemoral pain syndrome (PFPS). Materials and Methods: We selected 52 young adults suffering from anterior knee pain due to PFPS to participate. Then, we randomly assigned 26 patients to either the McConnell or the Kinesio taping groups. We measured their knee pain and gait parameters during stair ambulation before and after the interventions. For the measured data, we performed a paired t-test to evaluate the amount of change before and after the intervention within the groups and an independent t-test to compare the groups. Results: From the comparison within the groups, we found a significant difference in both groups in the anterior knee pain scale score (p < 0.05) and a significant difference between the groups as well (p < 0.05). As a result of the analysis of the gait parameters while ascending stairs in the comparison within the groups, both groups showed significant differences in all gait variables, except for the double-support stance (p < 0.05), and we found significant differences in all gait variables, except for the double-support stance, in the comparison between the groups (p < 0.05). Regarding the gait variables during stair descent in the comparison within the groups (p < 0.05), both groups showed significant differences in all of the gait variables; we noted significant differences in the double-support stance, step length, velocity, and cadence in the comparison between the groups (p < 0.05). Conclusions: The McConnell and Kinesio tapings were effective in improving knee pain and gait parameters during ambulation in patients with PFPS, but we found that the McConnell taping had a significant impact on pain reduction during stair ambulation, resulting in further improvement in the gait variables.

Does musculoskeletal pain interfere with motor learning in a gait adaptation task? A proof-of-concept study

BACKGROUND

Experimental pain during gait has been shown to interfere with learning a new locomotor task. However, very few studies have investigated the impact of clinical pain on motor learning due to the challenges associated with clinical populations.

OBJECTIVE

The first objective of this proof-of-concept study was to determine the feasibility to obtain two groups of participants with chronic ankle pathology with or without residual pain while walking. The second objective was to evaluate the impact of clinical musculoskeletal pain on motor learning during gait.

METHODS

Participants with chronic isolated ankle pathology were recruited and their personal and clinical characteristics were collected (functional performance, dorsiflexion maximal strength, range of motion). To assess motor acquisition (Day 1) and retention (Day 2), participants performed an adaptation task on two consecutive days that consisted of walking while experiencing a perturbing force applied to the ankle. The level of pain during the task was measured, and participants who reported pain were attributed to the Pain group and participants without pain to the No Pain group. Learning performance was assessed by measuring ankle kinematics (Mean plantarflexion absolute error) and learning strategy was assessed by measuring the Relative timing of error and the tibialis anterior (TA) electromyographic activity.

RESULTS

Twenty-five participants took part in the experiment. Eight (32%) were excluded because they could not be included in either the Pain or No Pain group due to the intermittent pain, leaving eight participants in the Pain group and nine in the No Pain group. Both groups were similar in terms of baseline characteristics. Musculoskeletal pain had no influence on learning performance, but the learning strategy were different between the two groups. The No Pain group showed a TA activity reduction before perturbation between the days, while the Pain group did not.

CONCLUSION

Some barriers were identified in studying musculoskeletal pain including the high rates of participants' exclusion, leading to a small sample size. However, we showed that it is feasible to investigate clinical pain and motor learning. From the results of this study, musculoskeletal pain has no influence on motor learning performance but influences the learning strategy.

Treatment Options for Patellofemoral Arthritis

PURPOSE OF REVIEW

To present a synthesis of recent literature regarding the treatment of patellofemoral arthritis RECENT FINDINGS: Risk factors of PFJ OA include patella malalignment or maltracking, injury to supportive structures including the MPFL, dysfunction of hamstring and quadriceps coordination, lower limb alignment, trochlear dysplasia, patellar trauma, or ACL surgery. Special physical exam maneuvers include patellar grind test, apprehension test, and lateral patellar tilt angle. Radiographs that should be obtained first-line include weight bearing bilateral AP, lateral, and Merchant views. CT and MRI are used to assess trochlear dysplasia, excessive patellar height, and TT-TG distance. Non-operative management options discussed include non-pharmacologic treatment (patient education, self-management, physical therapy, weight loss), ESWT, cold therapy, taping, bracing, and orthotics. Pharmacologic management options discussed include NSAIDs, acetaminophen, oral narcotics, and duloxetine. Injection therapies include glucocorticoids, hyaluronic acid, PRP, and other regenerative therapies (BMAC, adipose, or mesenchymal stem cells). Other treatment options include radiofrequency ablation and botulinum toxin. The algorithm for the surgical treatment of PFJ OA can begin with arthroscopic assessment of the PF articular cartilage to address mechanical symptoms and to evaluate/treat lateral soft tissue with or without overhanging lateral osteophytes. If patients fail to have symptomatic improvement, a TTO can be considered in those patients less than 50 years of age or active patients >50 years old. In patients with severe PFJ OA, refractory to the above treatments, PFA should be considered. While early PFA design and technique were less than encouraging, more recent implant design and surgical technique have demonstrated robust results in the literature. Patellofemoral osteoarthritis is a challenging orthopedic problem to treat, in that it can often affect younger patients, with otherwise well-functioning knees. It is a unique entity compared to TF OA with distinct epidemiology, biomechanics and risk factors and treatment options.

Comparison of flexion relaxation phenomenon between female yogis and matched non-athlete group

BACKGROUND

Trunk flexion is a common exercise during daily activities. Flexion relaxation phenomenon (FRP) occurs during forward bending in which there is a sudden silence of erector spinae (ES) muscles. The pattern of forward bending differs in yoga practitioners. This learned pattern probably predisposes yogis to injuries. The hypothesis of this study was that FRP differs in yogis in comparison to non-yogis individuals.

METHODS

This observational cross-sectional study was performed on 60 women assigned into yogis and non-athlete groups. Each participant was asked to bend forward and then return to the initial position. ES activity was recorded at L3 level, 4 cm from mid line during the trial. Trunk inclination and lumbar flexion angles were calculated at FRP onset and cessation moments.

RESULTS

The FRP occurred in 80% of yoga practitioners in comparison to 96.7% in the control group. Trunk inclination angle was significantly greater at FRP initiation in yogis compared to control group. Lumbar flexion angle was not different between the groups.

CONCLUSIONS

It is concluded that the altered pattern of forward bending observed in yogis may change patterns of ES muscles activity if it becomes part of a person's daily lifestyle which might predispose these muscles to fatigue and subsequent injuries; however, further studies are warranted for clarification.

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.

Is Isolated Hip Strengthening or Traditional Knee-Based Strengthening More Effective in Patients With Patellofemoral Pain Syndrome? A Systematic Review With Meta-analysis

Background:

Focus on the importance of hip muscle strength in patients with patellofemoral pain syndrome (PFPS) has recently increased. It is unknown whether patients with PFPS will benefit more from hip strengthening compared with traditional knee-based strengthening.

Purpose:

To compare the efficiency of isolated hip strengthening versus traditional knee-based strengthening for patients with PFPS.

Study Design:

Systematic review; Level of evidence, 2.

Methods:

We conducted a search for studies comparing isolated hip strengthening and knee-based strengthening by using the MEDLINE, Embase, and Cochrane Library electronic databases. The methodological quality of included studies was assessed using the PEDro scale. Predetermined variables from each study were extracted and analyzed.

Results:

A total of 5 comparative studies were included in this review; all studies were of moderate to high quality and reflected good internal and external validity. Pain (visual analog scale [VAS]) and function (Anterior Knee Pain Scale) scores improved in both the hip and knee groups after strengthening intervention, although no statistically significant differences were seen between groups in the pooled analysis. In 2 studies, VAS pain scores were reduced earlier for patients in the hip group than for those in the knee group (P < .05). In 1 study, improvement in Western Ontario and McMaster Universities Osteoarthritis Index function scores in the hip group was statistically superior compared with those in the knee group after intervention and at 6-month follow-up (P < .05). In 2 studies, patients in the hip group exhibited statistically greater hip abductor and extensor strength than did those in the knee group after intervention (P < .05).

Conclusion:

The best-available evidence suggests that overall, isolated hip strengthening and knee strengthening were equivalent for treatment of PFPS.

Prognostic factors for isolated medial patellofemoral ligament reconstruction: A systematic review

BACKGROUND

Evidence concerning the influence gender, age, and the time elapsed from the first dislocation to surgery in the outcomes of Medial Patella Femoral Ligament (MPFL) reconstruction are lacking. This systematic review was conducted to investigate whether patient characteristics have an influence in the clinical outcomes of MPFL reconstruction for patients with patellofemoral instability.

MATERIAL AND METHODS

This study followed the PRISMA guidelines. The main databases were accessed in February 2021. All the studies reporting outcomes of primary MPFL reconstruction in patients with recurrent patellofemoral instability were considered for inclusion. A multivariate analysis diagnostic tool was used to analyse the association between age, gender and time from injury to surgery and the surgical outcomes at last follow-up.

RESULTS

A total of 50 articles (2037 procedures) were included. The mean follow-up was 40.90 ± 24.8 months. The mean age was 23.6 ± 3.9 years. 64.3% (1309 of 2037 patients) were female. The mean time from injury to surgery was 64.5 ± 48.9 months. Women showed no statistically significant association with the Kujala score or complications. Older patients had a reduced risk to incur re-dislocations (P = 0.01) and revisions (P = 0.01). Longer time from injury to surgery was associated with greater risk to incur re-dislocations (P = 0.01), and with lower Kujala score (P < 0.0001). No other statistically significant association was evidenced.

CONCLUSION

The time span from the first patellar dislocation to the surgical reconstruction was a negative prognostic factor, while sex had no influence on surgical outcomes. The role of patients age on surgical outcomes remains unclear.

Effects of Trigger Point Dry Needling on Neuromuscular Performance and Pain of Individuals Affected by Patellofemoral Pain: A Randomized Controlled Trial

Purpose

To investigate the effects of trigger point dry needling (TrP-DN) on exercise-induced patellofemoral pain syndrome (PFPS).

Patients and Methods

In this randomized, single-blind, parallel-group trial, 50 patients with PFPS were randomly allocated to the following two groups: the TrP-DN group (n = 25) and the Sham needling group (n = 25). Patients in both groups were asked to perform a stretching exercise of the quadriceps daily after needling. The needling group received a single session of TrP-DN to trigger points (TrPs) in the vastus medialis oblique (VMO), vastus lateralis (VL), and rectus femoris muscles (once a week for 6 weeks), and the Sham group received placebo needling. Visual analogue scale (VAS) for pain intensity and Kujala questionnaire for the functional status were assessed before treatment, 3 and 6 weeks after treatment, and at the 3-month follow-up. The ratio of the myoelectric amplitude of the vastus medialis oblique and vastus lateralis muscles (VMO/VL) was assessed before treatment and 6 weeks after treatment.

Results

There was no significant difference in the general data between the two groups. The VAS scores and Kujala scores in the TrP-DN group were significantly improved and increased at the 3-week treatment visit, 6-week treatment visit, and 3-month follow-up compared to the scores before treatment; and the scores in the Sham group were only significantly improved at the 3-week treatment visit, and 6-week treatment visit. VAS scores in the TrP-DN group were significantly lower and Kujala scores were significantly higher at the 6-week treatment visit and the 3-month follow-up compared to those in the Sham group. The VMO/VL ratio in the TrP-DN group was significantly increased at the 6-week treatment visit compared to that before treatment.

Conclusion

TrP-DN at the quadriceps combined with stretch can reduce the pain, and improves the clinical symptoms and function, the VMO/VL ratio, and the coordination of VMO and VL in patients with PFPS.

Taping, Bracing, and Injection Treatment for Patellofemoral Pain and Patellar Tendinopathy

PURPOSE OF REVIEW

This article will focus on additional treatment options for the two most common causes of anterior knee pain, patellofemoral pain syndrome, and patellar tendinopathy. Conservative management is the first-line treatment for these conditions. For clinicians to maximize the efficacy of conservative treatment options for their patients, they must understand the most up-to-date literature evaluating the potential benefit of taping, bracing, and injections as adjunctive treatments for maximizing treatment success.

RECENT FINDINGS

Recent studies of bracing and taping have found them to be helpful for patients in the short-term management of pain and improving function. However, less is known about their exact mechanism but studies are encouraging that they have a subtle role in changing patellofemoral biomechanics. Injections remain a commonly used treatment for musculoskeletal conditions; however, the evidence for their use in patellofemoral pain and patellar tendinopathy is limited. The use of platelet-rich plasma (PRP), sclerosing, high volume, or stem cell injections is an exciting new area in the treatment of patellar tendinopathy. However, evidence at this time to recommend these treatments is lacking, and more well-designed studies are needed. The treatment of patellofemoral pain and patellar tendinopathy consists of a multi-faceted approach of physiotherapy and physical modalities. There is evidence for short-term use of taping and bracing for these conditions. The evidence for injections at this time is limited and remains under investigation. Future well-designed randomized controlled studies will provide insight into the efficacy of several different types of injections in the treatment of patellar tendinopathy. Physicians should feel comfortable integrating taping and bracing into their anterior knee pain treatment paradigm while making cautious use of invasive injections as adjunctive therapy.

Sex differences in neuromuscular control of quadriceps

PURPOSE

Patellofemoral pain syndrome (PFPS) is twice as prevalent in females as males, yet a few studies have evaluated differences in quadriceps muscle control between sexes or across force levels. This study investigated sex differences in quadriceps EMG onset times and amplitude at different force levels during isometric knee extension in asymptomatic males and females and in females with PFPS.

METHODS

Thirteen healthy males, 12 healthy females, and 10 females with PFPS performed isometric knee extension ramp contractions at 25%, 50%, and 75% of maximal voluntary contraction (MVC). Surface EMG was recorded from the vastus lateralis (VL), vastus medialis oblique (VMO), vastus medialis (VM), and rectus femoris (RF).

RESULTS

Healthy females showed delayed VL (222 ± 67 ms, p = 0.002), VMO (357 ± 101 ms, p = 0.001), and VM (258 ± 62 ms, p < 0.001) recruitment in comparison with healthy males. Healthy males activated the VL earlier than the VM (156 ± 51 ms, p = 0.02) and RF (379 ± 74 ms, p < 0.001), and at a similar time as the VMO; healthy females activated the VL earlier than the VM (192 ± 53 ms, p = 0.004) and VMO (239 ± 73 ms, p = 0.01). A lower VMO:VL activation ratio was found at 25% MVC (p < 0.001) than at higher force levels.

CONCLUSIONS

Delayed activation of the VMO relative to the VL has been proposed as a risk factor for PFPS. This study confirms a delay in VMO onset time in females.

Adaptation of muscle activation after patellar loading demonstrates neural control of joint variables

We evaluated whether the central nervous system (CNS) chooses muscle activations not only to achieve behavioral goals but also to minimize stresses and strains within joints. We analyzed the coordination between quadriceps muscles during locomotion in rats before and after imposing a lateral force on the patella. Vastus lateralis (VL) and vastus medialis (VM) in the rat produce identical knee torques but opposing mediolateral patellar forces. If the CNS regulates internal joint stresses, we predicted that after imposing a lateral patellar load by attaching a spring between the patella and lateral femur, the CNS would reduce the ratio between VL and VM activation to minimize net mediolateral patellar forces. Our results confirmed this prediction, showing that VL activation was reduced after attaching the spring whereas VM and rectus femoris (RF) activations were not significantly changed. This adaptation was reversed after the spring was detached. These changes were not observed immediately after attaching the spring but only developed after 3–5 days, suggesting that they reflected gradual processes rather than immediate compensatory reflexes. Overall, these results support the hypothesis that the CNS chooses muscle activations to regulate internal joint variables.

Update of Risk Factors, Diagnosis, and Management of Patellofemoral Pain

PURPOSE OF REVIEW

Patellofemoral pain is the most common cause of anterior knee pain. The purpose of this review is to examine the latest research on risk factors, physical examination, and treatment of patellofemoral pain to improve accuracy of diagnosis and increase use of efficacious treatment modalities.

RECENT FINDINGS

The latest research suggests patellofemoral pain pathophysiology is a combination of biomechanical, behavioral, and psychological factors. Research into targeted exercise therapy and other conservative therapy modalities have shown efficacy especially when used in combination. New techniques such as blood flow restriction therapy, gait retraining, and acupuncture show promise but require further well-designed studies. Patellofemoral pain is most commonly attributed to altered stress to the patellofemoral joint from intrinsic knee factors, alterations in the kinetic chain, or errors in training. Diagnosis can be made with a thorough assessment of clinical history and risk factors, and a comprehensive physical examination. The ideal treatment is a combination of conservative treatment modalities ideally individualized to the risk factors identified in each patient. Ongoing research should continue to identify biomechanical risk factors and new treatments as well as look for more efficient ways to identify patients who are amenable to treatments.

A randomized controlled trial comparing the long-term use of soft lumbosacral orthoses at two different pressures in patients with chronic nonspecific low back pain

BACKGROUND

There is concern that wearing soft lumbosacral orthoses for prolonged periods may impair motor function. Moreover, the pressure applied by lumbosacral orthoses on the abdominal wall is usually ignored when these orthoses are prescribed.

METHOD

In this randomized controlled trial study, 48 patients with chronic nonspecific low back pain were randomly divided into high pressure, normal pressure and control groups. All groups received medication for 4 weeks. The normal pressure and high pressure groups, in addition to medication, used soft lumbosacral orthoses at normal pressure and 50% increased pressure, respectively. Motor function outcome measures were strength, endurance, proprioception and electromyographic activity of the trunk muscles. Clinical outcome measures were pain and disability, which were evaluated in two sessions before and after a 4-week interval.

FINDINGS

Isometric strength, endurance and most of the electromyographic parameters were generally unaffected by wearing the lumbosacral orthosis. Pain improved in all groups, and disability and proprioception improved in the high pressure and normal pressure groups. Between-group differences in these three measures indicated better results in the lumbosacral orthoses groups than in the control group. The improvements in pain and proprioception were significantly greater in the high pressure group than the normal pressure group.

INTERPRETATION

Long-term use of lumbosacral orthoses had no significant adverse effects on motor function or clinical factors in patients with chronic low back pain. Increasing lumbosacral orthosis tightness may improve motor functioning and the clinical efficacy of the orthosis.

CLINICAL TRIAL REGISTRATION NUMBER

Code: IRCT201708192391N38.

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.

Trunk postural control during unstable sitting differs between patients with patellofemoral pain syndrome and healthy people: A cross-sectional study

BACKGROUND

Patellofemoral pain syndrome (PFPS) is a common orthopedic problem with a high prevalence among young women. Patients with PFPS have altered trunk muscle activity, impaired postural control and greater displacement of the center of pressure (COP) while standing. Training in unstable sitting, by putting more emphasis on trunk sensory receptors, may improve trunk proprioception by minimizing the role of the lower extremities. The aim of this study was to compare trunk postural control in healthy persons and in patients with PFPS.

METHODS

Twenty-one women diagnosed with PFPS and 21 healthy women volunteered to participate in this cross-sectional study. The participants were asked to maintain trunk postural balance on an unstable sitting device, and COP indices of trunk postural control were compared between groups.

RESULTS

All COP indices (e.g., mean anterior-posterior and lateral COP displacement, mean COP velocity and mean area of COP displacement) were significantly increased in participants with PFPS in comparison to healthy controls (P < 0.001). The effect sizes of all the indices were greater than 0.80.

CONCLUSIONS

Trunk postural control is impaired in patients with PFPS, and this finding has clinical implications for rehabilitation in patients with PFPS. Adding seated postural control training to conventional physical therapy management in patients with PFPS may have beneficial effects by emphasizing trunk proprioception while minimizing the role of the lower extremities.

Electromyographic activity of the hip and knee muscles during functional tasks in males with and without patellofemoral pain

BACKGROUND

Patellofemoral pain (PFP) is a common overuse injury in physically active individuals. It is characterized by anterior knee, retropatellar, or prepatellar pain associated with activities that increase patellofemoral joint stress such as squatting, stair ascending and descending, running, jumping, prolonged sitting, and kneeling. The etiology of PFP is believed to be multifactorial. Recently, proximal factors have been shown to influence the biomechanics of patellofemoral joint.

OBJECTIVE

The aim of the study was to assess hip and knee muscle activity during single leg stance and single leg squat in males with PFP and a control group without PFP.

METHODS

Eighteen males with PFP (age 24.2 ± 4.4 years) and 18 healthy subjects as controls (age 23.5 ± 3.8 years) were included. We evaluated gluteus medius, gluteus maximus, vastus medialis oblique (VMO), and vastus lateralis (VL) electromyographic (EMG) activity. The muscle activity and reaction time of the proposed muscles were assessed during single leg stance and single leg squat tasks. Independent t-test was used to identify significant differences between PFP and control groups.

RESULTS

No difference in activity of the gluteus maximus muscle was found in either task (p > 0.5). Significant differences were found in activity of gluteus medius and VMO in both tasks (p < 0.05). VL muscle activity had significant difference in single leg stance (p = 0.01), however, had no significant difference in single leg squat (p = 0.1). No significant differences were found in reaction time of the four studied muscles during both single leg stance and single leg squat (p > 0.5).

CONCLUSION

Males with PFP demonstrated altered gluteus medius, VMO, and VL muscle activity during single leg stance and single leg squat compared to healthy subjects. Gluteus maximus activity did not show any changes between groups. Moreover, muscle recruitment patterns were different between PFP and healthy groups.

Vastus lateralis and vastus medialis produce distinct mediolateral forces on the patella but similar forces on the tibia in the rat

Improper activation of the quadriceps muscles vastus medialis (VM) and vastus lateralis (VL) has been implicated in the development of patellofemoral pain (PFP). This explanation of PFP assumes that VM and VL produce opposing mediolateral forces on the patella. Although studies have provided evidence for opposing actions of VM and VL on the patella, other studies have suggested that their actions might be similar. In this study, we took advantage of the experimental accessibility of the rat to directly measure the forces on the patella produced by VM and VL. We found that VM and VL produce opposing mediolateral forces on the patella when the patella was lifted away from the femur. These distinct mediolateral forces were not transmitted to the tibia, however: forces measured at the distal tibia were very similar for VM and VL. Further, when the patella was placed within the trochlear groove, the forces on the patella produced by VM and VL were very similar to one another. These results suggest that mediolateral forces produced by VM and VL are balanced by reaction forces from the trochlear groove and so are not transmitted to the tibia. These results provide a rich characterization of the mechanical actions of VM and VL and have implications about the potential role of these muscles in PFP and their neural control during behavior.

Effect of experimental muscle pain on the acquisition and retention of locomotor adaptation: different motor strategies for a similar performance

As individuals with musculoskeletal disorders often experience motor impairments, contemporary rehabilitation relies heavily on the use of motor learning principles. However, motor impairments are often associated with pain. Although there is substantial evidence that muscle pain interferes with motor control, much less is known on its impact on motor learning. The objective of the present study was to assess the effects of muscle pain on locomotor learning. Two groups (Pain and Control) of healthy participants performed a locomotor adaptation task (robotized ankle-foot orthosis perturbing ankle movements during swing) on two consecutive days. On day 1 (acquisition), hypertonic saline was injected in the tibialis anterior (TA) muscle of the Pain group participants, while Control group participants were pain free. All participants were pain free on day 2 (retention). Changes in movement errors caused by the perturbation were assessed as an indicator of motor performance. Detailed analysis of kinematic and electromyographic data provided information about motor strategies. No between-group differences were observed on motor performance measured during the acquisition and retention phases. However, Pain group participants had a residual movement error later in the swing phase and smaller early TA activation than Control group participants, thereby suggesting a reduction in the use of anticipatory motor strategies to overcome the perturbation. Muscle pain did not interfere with global motor performance during locomotor adaptation. The different motor strategies used in the presence of muscle pain may reflect a diminished ability to anticipate the consequences of a perturbation. NEW & NOTEWORTHY This study shows that experimental muscle pain does not influence global motor performance during the acquisition or next-day retention phases of locomotor learning. This contrasts with previous results obtained with cutaneous pain, emphasizing the risk of directly extrapolating from one pain modality to another. Muscle pain affected motor strategies used when performing the task, however: it reduced the ability to use increased feedforward control to overcome the force field.

Predicting muscle forces during the propulsion phase of single leg triple hop test

Functional biomechanical tests allow the assessment of musculoskeletal system impairments in a simple way. Muscle force synergies associated with movement can provide additional information for diagnosis. However, such forces cannot be directly measured noninvasively. This study aims to estimate muscle activations and forces exerted during the preparation phase of the single leg triple hop test. Two different approaches were tested: static optimization (SO) and computed muscle control (CMC). As an indirect validation, model-estimated muscle activations were compared with surface electromyography (EMG) of selected hip and thigh muscles. Ten physically healthy active women performed a series of jumps, and ground reaction forces, kinematics and EMG data were recorded. An existing OpenSim model with 92 musculotendon actuators was used to estimate muscle forces. Reflective markers data were processed using the OpenSim Inverse Kinematics tool. Residual Reduction Algorithm (RRA) was applied recursively before running the SO and CMC. For both, the same adjusted kinematics were used as inputs. Both approaches presented similar residuals amplitudes. SO showed a closer agreement between the estimated activations and the EMGs of some muscles. Due to inherent EMG methodological limitations, the superiority of SO in relation to CMC can be only hypothesized. It should be confirmed by conducting further studies comparing joint contact forces. The workflow presented in this study can be used to estimate muscle forces during the preparation phase of the single leg triple hop test and allows investigating muscle activation and coordination.

VASTUS LATERALIS OBLIQUE ACTIVITY DURING GAIT OF SUBJECTS WITH PATELLOFEMORAL PAIN

ABSTRACT Introduction: So far, little is known about the behavior of electromyographic activity of vastus lateralis oblique muscle during treadmill gait in subjects with and without patellofemoral pain syndrome. Objective: The purpose of this study was to investigate the electromyographic activity of the patellar stabilizers muscles and the angle of the knee joint flexion in subjects with and without patellofemoral pain syndrome. Method: Fifteen subjects without (21 ± 3 years) and 12 with patellofemoral pain syndrome (20 ± 2 years) were evaluated. The electromyographic activity and flexion angle of the knee joint were obtained during gait on the treadmill with a 5 degree inclination. Results: The knee flexion angle was significantly lower in the subjects with patellofemoral pain syndrome when compared with the healthy controls. The electromyographic activity of vastus lateralis longus was significantly greater during gait on the treadmill with inclination in subjects with patellofemoral pain syndrome. The results also showed that the electromyographic activity of vastus lateralis oblique and vastus medialis oblique were similar in both groups, regardless of the condition (with/without inclination). Conclusion: We have shown that knee kinematics during gait differs among patients with and without patellofemoral pain syndrome and healthy controls and that a different motor strategy persists even when the pain is no longer present. In addition, the findings suggested that the vastus lateralis oblique has a minor role in patellar stability during gait.

Quantifying knee mechanics during balance training exercises

Patellofemoral pain (PFP) is common among runners and those recovering from anterior cruciate ligament reconstruction. Training programs designed to prevent or treat injuries often include balance training, although balance interventions have been reported to coincide with more knee injuries. Knowledge of the effect of balance exercises on knee mechanics may be useful when designing training programs. High knee abduction moment has been implicated in the development of PFP, and imbalance between vastus lateralis (VL) and vastus medialis oblique (VMO) may contribute to patellofemoral stress. The purpose was to quantify knee abduction moment and vasti muscle activity during balance exercises. Muscle activity of VMO and VL, three-dimensional lower-extremity kinematics, and ground reaction forces of healthy recreational athletes (12M, 13F) were recorded during five exercises. Peak knee abduction moment, ratio of VMO:VL activity, and delay in onset of VMO relative to VL were quantified for each exercise. The influence of sex and exercise on each variable was determined using a mixed-model ANOVA. All analyses indicated a significant main effect of exercise, p<0.05. Follow-up comparisons showed low peak knee abduction moment and high VMO:VL ratio for the task with anterior-posterior motion. Delay of VMO relative to VL was similar among balance board tasks.

Effectiveness of Manual Therapy Combined With Physical Therapy in Treatment of Patellofemoral Pain Syndrome: Systematic Review

OBJECTIVES

The purpose of this study was to conduct a review of randomized controlled trials (RCTs) to determine the treatment effectiveness of the combination of manual therapy (MT) with other physical therapy techniques.

METHODS

Systematic searches of scientific literature were undertaken on PubMed and the Cochrane Library (2004-2014). The following terms were used: "patellofemoral pain syndrome," "physical therapy," "manual therapy," and "manipulation." RCTs that studied adults diagnosed with patellofemoral pain syndrome (PFPS) treated by MT and physical therapy approaches were included. The quality of the studies was assessed by the Jadad Scale.

RESULTS

Five RCTs with an acceptable methodological quality (Jadad ≥ 3) were selected. The studies indicated that MT combined with physical therapy has some effect on reducing pain and improving function in PFPS, especially when applied on the full kinetic chain and when strengthening hip and knee muscles.

CONCLUSIONS

The different combinations of MT and physical therapy programs analyzed in this review suggest that giving more emphasis to proximal stabilization and full kinetic chain treatments in PFPS will help better alleviation of symptoms.

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.

Kinematic and electromyographic analysis in patients with patellofemoral pain syndrome during single leg triple hop test

Possible delays in pre-activation or deficiencies in the activity of the dynamic muscle stabilizers of the knee and hip joints are the most common causes of the patellofemoral pain syndrome (PFPS). The aim of the study was to compare kinematic variables and electromyographic activity of the vastus lateralis, biceps femoris, gluteus maximus and gluteus medius muscles between patients with PFPS and health subjects during the single leg triple hop test (SLTHT). This study included 14 female with PFPS (PFPS group) and 14 female healthy with no history of knee pain (Healthy group). Kinematic and EMG data ware collected through participants performed a single session of the SLTHT. The PFPS group exhibited a significant increase (p<0.05) in the EMG activity of the biceps femoris and vastus lateralis muscles, when compared with the healthy group in pre-activity and during the stance phase. This same result was also found for the vastus lateralis muscle (p<0.05) when analyzing the EMG activity during the eccentric phase of the stance phase. In kinematic analysis, no significant differences were found between the groups. These results indicate that biceps femoris and vastus lateralis muscles mainly during the pre-activation phase and stance phases of the SLTHT are more active in PFPS group among healthy group.

Impairments of postural stability, core endurance, fall index and functional mobility skills in patients with patello femoral pain syndrome

BACKGROUND

Postural control allows performance of daily and sports activities. The previous studies show that postural sway inceases in orthopaedic injuries such as osteoarthritis and total knee arthroplasty.

OBJECTIVE

To compare postural sway, risk of falling and function between individuals with and without patellofemoral pain syndrome (PFS).

METHODS

This study included 22 subjects with patellofemoral pain syndrome, age-matched pain-free 22 females serving as a control group. Visual anolog scale and Kujala were used to evaluate the pain. Posturographic assesment was performed by Tetrax posturographic device. Biering Modified Sorenson test for extensor endurance and sit-up test for flexor endurance were used for the evaluation of trunk endurance. Timed get-up and go test was used for lower extremity function. The Student's t Test was used to compare variables between the groups. The Pearson correlation coefficients were calculated to examine correlation between the quantitative variables.

RESULTS

Postural sway included eyes open without pillow, eyes open on pillow, eyes closed on pillow, risk of falling, function and postural stabilization included flexor endurance, extansor endurance are impared in patient with patellofemoral pain syndrome when compare to controls. In subjects with PFPS increased postural sway significantly associated with body mass index (r= 0.52), pain duration (r= 0.43), postural control (extansor endurance) (r= -0.50) and risk of falling (r= 0.62) on pillow with open eyes. In addition we found function significantly related with postural control (extansor endurance and flexor endurance) (r= -0.59 and r= -0.59) and risk of falling (r= 0.77)CONCLUSIONS: Decreased neuromuscular control of the trunk core and increased postural sway and falling risk were found in patients with PFPS. Patients may be evaluated for deficits in postural control and falling risk before treatment.

Core muscle recruitment pattern during voluntary heel raises is different between patients with patellofemoral pain and healthy individuals

BACKGROUND

Recent studies suggest that the inconsistent outcomes of patellofemoral pain (PFP) treatment may result from the unclear understanding of changes in the structures remote from the knee joint. Due to the crucial influence of core stability on the knee function, this study aimed to evaluate the recruitment pattern of core muscles in individuals with and without PFP.

METHODS

Sixty women aged 18 to 40years, including 30 subjects diagnosed with PFP and 30 healthy controls rose on to their toes as quickly and strongly as possible in response to a sound alarm in standing position. Electromyographic onsets of the transversus abdominis (TrA)/internal oblique (IO), erector spinae (ES), and gluteus medius (GM) muscles were expressed relative to the electromyographic onset of the prime mover (i.e. soleus). Independent t-tests were performed to compare the onsets of each muscle between the groups. The nonparametric Friedman test and the post-hoc of Wilcoxon signed-rank test were used to describe the muscle activation pattern within the groups.

RESULTS

The results revealed different recruitment patterns of the core muscles between the groups. In the healthy group the GM and TrA/IO contracted, almost simultaneously, in anticipation of the prime mover contraction (sol). However, in PFP subjects a significant delay in the contraction of TrA/IO changed the pattern of muscle activation.

CONCLUSION

The findings demonstrate that muscular stabilization of spine is altered in the presence of PFP and suggest that treatment techniques aimed at improving core stability could be appropriate in the management of PFP.

Additional Effects of an Individualized Risk Factor-Based Approach on Pain and the Function of Patients With Patellofemoral Pain Syndrome: A Randomized Controlled Trial

OBJECTIVE

To investigate the clinical efficacy of adding risk factor-based approach (including appropriate exercises and orthoses) to routine quadriceps strengthening exercise with respect to pain and function in patients with patellofemoral pain syndrome (PFPS).

DESIGN

A parallel group nonblinded randomized controlled trial with 12-week follow-up.

SETTING

An outpatient Sports Medicine Clinic of Tehran University of Medical Sciences, Tehran, Iran.

PARTICIPANTS

Patients (both sexes, 18-40 years) with clinically diagnosed PFPS of the duration over 2 months.

INTERVENTION

The intervention group received an individualized program, including exercise therapy plus risk factor modification, and was instructed to practice the tailored interventions at home for 12 weeks. The control group received an exercise program, only focusing on quadriceps strengthening.

MAIN OUTCOME MEASURES

The primary outcomes were pain severity during the activities of daily living (0- to 100-point visual analog scale), and function (0- to 100-point Kujala patellofemoral score) at a 12-week follow-up.

RESULTS

A total of 53 participants completed the trial: 26 in the intervention and 27 in the control group. After 12 weeks, both groups showed improvements in pain and function, but the changes were significantly greater in the intervention group with regard to pain [adjusted difference, -14.90; 95% confidence interval (CI), -5.86 to -23.93, P = 0.002], and function (adjusted difference, 6.82; 95% CI, 2.54-11.10, P = 0.002).

CONCLUSIONS

Assessment and modification of the risk factors may add to the treatment effects on pain and function at a 12-week follow-up in patients with PFPS. These findings may lead to a more comprehensive clinical approach to this very common problem.

CLINICAL RELEVANCE

It seems that incorporating risk factor assessment into our clinical practice may add to treatment effects with regard to pain and function in patients with PFPS.

Neuromuscular and physiological variables evolve independently when running immediately after cycling

During the early period of running after cycling, EMG patterns of the leg are modified in only some highly trained triathletes. The majority of studies have analysed muscle EMG patterns at arbitrary, predetermined time points. The purpose of this study was to examine changes to EMG patterns of the lower limb at physiologically determined times during the cycle-run transition period to better investigate neuromuscular adaptations. Six highly trained triathletes completed a 10 m in isolated run (IR), 30 min of rest, then a 20 min cycling procedure, before a 10 min transition run (C-R). Surface EMG activity of eight lower limb muscles was recorded, normalised and quantified at four time points. Oxygen uptake and heart rate values were also collected. Across all muscles, mean (± SD) EMG patterns, demonstrated significant levels of reproducibility for each participant at all four time points (α < 0.05; r = 0.52-0.97). Mean EMG patterns during C-R correlated highly with the IR patterns (α < 0.05). These results show that EMG patterns during subsequent running are not significantly affected by prior cycling. However, variability of muscle recruitment activity does appear to increase during C-R transition when compared to IR.

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.

Characteristics of stabilizer muscles: a systematic review

PURPOSE

To identify the main characteristics, based on available evidence, of stabilizer muscles to inform the development of a definition of stabilizer muscles.

METHODS

Electronic databases were systematically searched for relevant literature from the databases' inception to June 2013 using keywords related to stability, muscles, and characteristics of stabilizer muscles. Studies that provided at least one characteristic of a stabilizer muscle were included. For the quality assessment, all included articles were categorized as either experimental or opinion-based studies. Methodological quality was assessed using a customized checklist, and data were analyzed with a narrative synthesis involving content analysis. The number of articles providing either direct evidence supporting a link between the characteristic and joint stability or indirect evidence that a muscle considered to be a stabilizer has that characteristic determined the level of significance of that characteristic for stabilizer muscles.

RESULTS

A total of 77 studies met the inclusion criteria. The highest number of articles providing supporting evidence that a particular muscle characteristic plays a stabilizing role related to biomechanical characteristics (27 articles), followed by neurological characteristics (22 articles) and anatomical/physiological characteristics (4 articles).

CONCLUSION

Based on a synthesis of supporting evidence from the literature, stabilizer muscles can be defined as muscles that contribute to joint stiffness by co-contraction and show an early onset of activation in response to perturbation via either a feed-forward or a feedback control mechanism. These results may guide researchers to investigate which muscles exhibit these characteristics to determine whether particular muscles have a stabilizer rather than a prime mover role during normal functioning.

ELECTROMYOGRAPHIC ANALYSIS OF LEG EXTENSION EXERCISE DURING DIFFERENT ANKLE AND KNEE POSITIONS

The imbalance between vastus medialis oblique (VMO) and vastus lateralis (VL) strength is one of the main factor for patellofemoral pain syndrome (PFPS) onset, related to improper alignment of the patella. The aim of this paper is to investigate the effects of knee flexion, knee rotation and ankle flexion attitudes on the activity of the VMO and VL muscles during unilateral maximal voluntary isometric contraction (MIVC) of the quadriceps femoris. Eighteen healthy subjects volunteered for the study. Five conditions for two different knee flexion angles (90°; 30°) were tested using leg extension machine: Neutral (N) condition, maximal knee medial rotation (MR), maximal knee lateral rotation (LR), maximal ankle plantarflexion (PF) and maximal ankle dorsiflexion (DF). Data were normalized in order to calculate the normalized VMO/VL ratio. The normalized VMO/VL ratio for all the conditions occurred at 90° of knee flexion was higher than the same conditions at 30° of knee flexion (p = 0.02). No statistical differences between conditions at the same knee angle and for angle x condition interaction were observed (p > 0.05). These findings suggest that knee flexion should be the first variable to be managed during isometric knee extension movement performed by leg extension machine, in order to increase VMO/VL ratio.

Alterations in patellofemoral kinematics following vastus medialis transection in the anterior cruciate ligament deficient rabbit knee

BACKGROUND

Anterior cruciate ligament deficiency and quadriceps muscle weakness are considered to be important risk factors for aberrant patellar tracking and subsequent patellofemoral osteoarthritis. However, data from in vivo experiments looking at dynamic patellar joint kinematics and muscle force are scarce. Therefore, the purpose of this study was to evaluate the effects of anterior cruciate ligament transection and loss of vastus medialis force on patellar tracking in the rabbit knee in vivo.

METHODS

Eight skeletally mature New Zealand White Rabbits, weighing 6.0kg (0.6kg standard deviation) were used. The experimental trials consisted of active, concentric and eccentric movements of the knee joint. Measurements were performed with the intact, the anterior cruciate ligament deficient, and the vastus medialis transected knee. Patellofemoral kinematics (shift, rotation) were quantified from high speed video.

FINDINGS

Following anterior cruciate ligament transection, patellar tracking occurred more laterally, and caused a significant lateral rotation of the patella. The addition of vastus medialis transection did not alter patellar tracking or rotation significantly for any of the force-matched experimental conditions.

INTERPRETATION

The loss of the anterior cruciate ligament results in lateral patellar shift and rotation while the loss of vastus medialis muscle force does not affect patellar tracking or rotation in the anterior cruciate ligament deficient knee. We suggest that the current results should be considered carefully in future interpretations of knee extensor imbalance. More research is needed to describe the contribution of vastus medialis muscle strength to medial patellofemoral stability and confirm these results in the human knee.

Influência de diferentes tipos de calçado na atividade eletromiográfica do músculo quadríceps de mulheres ao subir e descer degrau

INTRODUÇÃO: A síndrome da dor femoropatelar (SDFP) é caracterizada por dor difusa na região retropatelar, aumentada durante realização de tarefas diárias, tais como subir e descer escadas e ajoelhar. A SDFP tem maior prevalência em mulheres jovens e sua etiologia não é totalmente conhecida. OBJETIVO: Avaliar a influência do uso de diferentes tipos de calçados na atividade dos músculos estabilizadores da patela durante as tarefas de subir e descer degrau. MATERIAIS E MÉTODOS: Participaram do estudo dez mulheres saudáveis e dez mulheres com SDFP. As voluntárias realizaram as tarefas de subir e descer um degrau em três situações: descalças, usando tênis e salto alto de 10 cm. Durante a realização das tarefas, foi registrada com eletrodos superficiais a atividade eletromiográfica dos músculos vasto medial oblíquo (VMO), vasto lateral (VL) e reto femoral (RF). A comparação intergrupos foi realizada com o teste t não pareado; para a análise intragrupo, utilizou-se ANOVA com medidas repetidas e post hoc Tukey, todos com um nível de significância de 5%. RESULTADOS: Os resultados demonstraram, no grupo controle, aumento da atividade do VMO nas tarefas concêntrica e excêntrica realizadas com salto alto. No entanto, no grupo SDFP, a atividade do VMO não foi influenciada em nenhuma das condições testadas. Não foram observadas diferenças estatísticas na razão VMO/VL e no tempo de ativação dos músculos. CONCLUSÃO: Os resultados sugerem que em mulheres assintomáticas uso do calçado de salto alto modificou a atividade de todos os músculos. Entretanto, mulheres com SDFP não apresentaram alterações no VMO.

Patellofemoral pain syndrome and modifiable intrinsic risk factors; how to assess and address?

Patellofemoral pain syndrome (PFPS) is a very common disorder of the knee. Due to multiple forces influencing the patellofemoral joint, clinical management of this ailment is particularly intricate. Patellofemoral pain syndrome has a multifactorial nature and multiple parameters have been proposed as potential risk factors, classified as intrinsic or extrinsic. Some of the intrinsic risk factors are modifiable and may be approached in treatment. A number of modifiable risk factors have been suggested, including quadriceps weakness, tightness of hamstring, iliopsoas and gastrosoleus muscles, hip muscles dysfunction, foot overpronation, tightness of iliotibial band, generalised joint laxity, limb length discrepancy, patellar malalignment and hypermobility. In general, the routine approach of physicians to this problem does not include assessment and modification of these risk factors and therefore, it may negatively affect the management outcomes. Changing this approach necessitates an easy and practical protocol for assessment of modifiable risk factors and effective and feasible measures to address them. In this review, we aimed to introduce assessment and intervention packages appropriate for this purpose.

Influência do calçado de salto alto na atividade eletromiográfica do músculo quadríceps em mulheres com e sem síndrome da dor femoropatelar durante a tarefa de levantar e sentar

O objetivo do estudo foi analisar a influência do calçado de salto alto na atividade eletromiográfica (EMG) do músculo quadríceps durante a tarefa de sentar e levantar. Participaram deste estudo 10 voluntárias assintomáticas com 20,2±3,0 anos e 10 voluntárias com síndrome da dor femoropatelar (SDFP) com 21,3±3,4 anos. As voluntárias executaram a tarefa de sentar e levantar em 3 diferentes condições: descalças, com tênis e com calçado de salto de 10 cm. A atividade EMG do vasto medial oblíquo (VMO), vasto lateral (VL) e reto femoral (RF) foi registrada durante a execução das tarefas por meio de eletrodos de superfície simples diferencial conectados ao eletromiógrafo. Para comparação entre grupos e tarefas, foi utilizado o teste ANOVA com medidas repetidas e o post hoc do teste de Tukey (p<0,05). Os resultados demonstraram maior atividade EMG do músculo VMO, no grupo Controle, durante as tarefas de levantar e sentar utilizando o salto alto. No grupo SDFP, foi observado aumento da atividade EMG do VL na tarefa de levantar do banco e diminuição da razão VMO:VL com o uso do salto alto. Os resultados mostraram que o uso do salto alto pode provocar um aumento da atividade do VL em relação ao VMO em mulheres com SDFP, fato esse que pode colaborar para o mau alinhamento patelar e agravamento da SDFP. Portanto, os resultados sugerem que esse tipo de calçado deve ser evitado por mulheres com SDFP.

Altered hip muscle forces during gait in people with patellofemoral osteoarthritis

OBJECTIVES

The study aimed to (1) assess whether higher vasti (VASTI), gluteus medius (GMED), gluteus maximus (GMAX) and gluteus minimus (GMIN) forces are associated with participant characteristics (lower age, male gender) and clinical characteristics (lower radiographic disease severity, lower symptom severity and higher walking speed); and (2) determine whether hip and knee muscle forces are lower in people with patellofemoral joint (PFJ) osteoarthritis (OA) compared to those without PFJ OA.

DESIGN

Sixty participants with PFJ OA and 18 (asymptomatic, no radiographic OA) controls ≥40 years were recruited from the community or via referrals. A three-dimensional musculoskeletal model was used in conjunction with optimisation theory to calculate lower-limb muscle forces during walking. Associations of peak muscle forces with participant and clinical characteristics were conducted using Pearson's r or independent t-tests and between-group comparisons of mean peak muscle forces performed with walking speed as a covariate.

RESULTS

Peak muscle forces were not significantly associated with participant, symptomatic or radiographic-specific characteristics. Faster walking speed was associated with higher VASTI muscle force in the PFJ OA (r = 0.495; P < 0.001) and control groups (r = 0.727; P = 0.001) and higher GMAX muscle force (r = 0.593; P = 0.009) in the control group only. Individuals with PFJ OA (N = 60) walked with lower GMED and GMIN muscle forces than controls (N = 18): GMED, mean difference 0.15 [95% confidence interval (CI): 0.01 to 0.29] body weight (BW); GMIN, 0.03 [0.01 to 0.06] BW. No between-group differences were observed in VASTI or GMAX muscle force: VASTI, 0.10 [-0.11 to 0.31] BW; GMAX, 0.01 [-0.11 to 0.09] BW.

CONCLUSION

Individuals with PFJ OA ambulate with lower peak hip abductor muscle forces than their healthy counterparts.

Alterations in in vivo knee joint kinematics following a femoral nerve branch block of the vastus medialis: Implications for patellofemoral pain syndrome

BACKGROUND

A potential source of patellofemoral pain, one of the most common problems of the knee, is believed to be altered patellofemoral kinematics due to a force imbalance around the knee. Although no definitive etiology for this imbalance has been found, a weak vastus medialis is considered a primary factor. Therefore, this study's purpose was to determine how the loss of vastus medialis obliquus force alters three-dimensional in vivo knee joint kinematics during a volitional extension task.

METHODS

Eighteen asymptomatic female subjects with no history of knee pain or pathology participated in this IRB approved study. Patellofemoral and tibiofemoral kinematics were derived from velocity data acquired using dynamic cine-phase contrast MRI. The same kinematics were then acquired immediately after administering a motor branch block to the vastus medialis obliquus using 3-5ml of 1% lidocaine. A repeated measures analysis of variance was used to test the null hypothesis that the post- and pre-injection kinematics were no different.

FINDINGS

The null hypothesis was rejected for patellofemoral lateral shift (P=0.003, max change=1.8mm, standard deviation=1.7mm), tibiofemoral lateral shift (P<0.001, max change=2.1mm, standard deviation=2.9mm), and tibiofemoral external rotation (P<0.001, max change=3.7°, standard deviation=4.4°).

INTERPRETATION

The loss of vastus medialis obliquus function produced kinematic changes that mirrored the axial plane kinematics seen in individuals with patellofemoral pain, but could not account for the full extent of these changes. Thus, vastus medialis weakness is likely a major factor in, but not the sole source of, altered patellofemoral kinematics in such individuals.

Patellofemoral pain: proximal, distal, and local factors, 2nd International Research Retreat

Patellofemoral pain (PFP) is one of the most common lower extremity conditions seen in orthopaedic practice. The mission of the second International Patellofemoral Pain Research Retreat was to bring together scientists and clinicians from around the world who are conducting research aimed at understanding the factors that contribute to the development and, consequently, the treatment of PFP. The format of the 2.5-day retreat included 2 keynote presentations, interspersed with 6 podium and 4 poster sessions. An important element of the retreat was the development of consensus statements that summarized the state of the research in each of the 4 presentation categories. In this supplement, you will find the consensus documents from the meeting, as well as the keynote addresses, schedule, and platform and poster presentation abstracts.

The effect of gender on force, muscle activity, and frontal plane knee alignment during maximum eccentric leg-press exercise

PURPOSE

To investigate for gender differences during eccentric leg-press exercise. Tears of the anterior cruciate ligament (ACL) are considered to be related to eccentric tasks, altered neuromuscular control (e.g., reduced co-contraction of hamstrings), and increased knee abduction (valgus alignment). Based on these observations and the fact that ACL tears are more common in women, it was hypothesized that men and women differ significantly with regard to key parameters of force, knee stabilization, and muscle activity when exposed to maximum eccentric leg extension.

METHODS

Thirteen women and thirteen men were matched for age and physical activity. They performed maximum isokinetic eccentric leg-pressing against footplates of varied stability. The latter was done because earlier studies had shown that perturbational test conditions might be relevant in respect of ACL injuries. Key parameters of force, frontal plane knee stabilization, and muscle recruitment of significant muscles crossing the knee were recorded.

RESULTS

The 'force stabilization deficit' (difference between maximum forces under normal and perturbed leg-pressing) did not differ significantly between genders. Likewise, parameters of muscle activity and frontal plane leg stabilization revealed no significant differences between men and women.

CONCLUSION

This study is novel, in that gender differences in parameters of force, muscle activity, and leg kinematic were investigated during functional conditions of eccentric leg-pressing. No gender differences were observed in the measured parameters. However, the conclusion should be viewed with caution because the findings concurred with, but also contrasted, previous research in this field.

LEVEL OF EVIDENCE

Diagnostic study, Level III.

Risk factors for patellofemoral pain syndrome: a systematic review

STUDY DESIGN

Systematic review.

OBJECTIVES

To systematically outline the risk factors for patellofemoral pain syndrome (PFPS).

BACKGROUND

PFPS is the most commonly diagnosed condition in young individuals with knee complaints. High incidence among athletes suggests a possibility of prevention. The first step toward prevention is identification of possible risk factors.

METHODS

Prospective studies that included 20 or more patients with PFPS and examined at least 1 possible risk factor for PFPS were included. An assessment list was applied to evaluate the quality of the studies. A meta-analysis was conducted using a random-effects model. Significant differences were based on calculated mean differences, with matching 95% confidence intervals (CIs). For dichotomous data, odds ratios or relative risks were calculated.

RESULTS

Of the 3845 potentially relevant articles, 7 were included in this review. These studies examined a total of 135 variables, and pooling was possible for 13 potential risk factors. The pooled data showed that knee extension peak torques were significantly lower in the PFPS group than in controls. Mean differences in torque, with negative differences reflecting lower means in the PFPS group, were as follows: (a) standardized relative to body weight at 60°/s, -0.24 Nm (95% CI: -0.39, -0.09); (b) standardized relative to body weight at 240°/s, -0.11 Nm (95% CI: -0.17, -0.05); (c) standardized relative to body mass index at 60°/s, -0.84 Nm (95% CI: -1.23, -0.44); (d) standardized relative to body mass index at 240°/s, -0.32 Nm (95% CI: -0.52, -0.12); (e) nonstandardized in a concentric mode at 60°/s, -17.54 Nm (95% CI: -25.53, -9.54); (f) nonstandardized in a concentric mode at 240°/s, -7.72 Nm (95% CI: -12.67, -2.77).

CONCLUSION

Weaker knee extension strength, expressed by peak torque, appears to be a risk factor for PFPS, based on meta-analyses of pooled results from multiple studies. Because several other risk factors for PFPS were described only in single studies, these additional risk factors, as well as those with conflicting evidence, need to be confirmed in future studies.

LEVEL OF EVIDENCE

Prognosis, level 1a-.