Gait analysis in patients with anterior knee pain

Kinematic and Kinetic Gait Characteristics in People with Patellofemoral Pain: A Systematic Review and Meta-analysis

BACKGROUND

Patellofemoral pain (PFP) is a prevalent knee condition with many proposed biomechanically orientated etiological factors and treatments.

OBJECTIVE

We aimed to systematically review and synthesize the evidence for biomechanical variables (spatiotemporal, kinematic, kinetic) during walking and running in people with PFP compared with pain-free controls, and determine if biomechanical variables contribute to the development of PFP.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

We searched Medline, CINAHL, SPORTDiscus, Embase, and Web of Science from inception to October 2021.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

All study designs (prospective, case-control [± interventional component, provided pre-intervention data were reported for both groups], cross-sectional) comparing spatiotemporal, kinematic, and/or kinetic variables during walking and/or running between people with and without PFP.

RESULTS

We identified 55 studies involving 1300 people with PFP and 1393 pain-free controls. Overall pooled analysis identified that people with PFP had slower gait velocity [moderate evidence, standardized mean difference (SMD) - 0.50, 95% confidence interval (CI) - 0.72, - 0.27], lower cadence (limited evidence, SMD - 0.43, 95% CI - 0.74, - 0.12), and shorter stride length (limited evidence, SMD - 0.46, 95% CI - 0.80, - 0.12). People with PFP also had greater peak contralateral pelvic drop (moderate evidence, SMD - 0.46, 95% CI - 0.90, - 0.03), smaller peak knee flexion angles (moderate evidence, SMD - 0.30, 95% CI - 0.52, - 0.08), and smaller peak knee extension moments (limited evidence, SMD - 0.41, 95% CI - 0.75, - 0.07) compared with controls. Females with PFP had greater peak hip flexion (moderate evidence, SMD 0.83, 95% CI 0.30, 1.36) and rearfoot eversion (limited evidence, SMD 0.59, 95% CI 0.03, 1.14) angles compared to pain-free females. No significant between-group differences were identified for all other biomechanical variables. Data pooling was not possible for prospective studies.

CONCLUSION

A limited number of biomechanical differences exist when comparing people with and without PFP, mostly characterized by small-to-moderate effect sizes. People with PFP ambulate slower, with lower cadence and a shortened stride length, greater contralateral pelvic drop, and lower knee flexion angles and knee extension moments. It is unclear whether these features are present prior to PFP onset or occur as pain-compensatory movement strategies given the lack of prospective data.

TRIAL REGISTRATION

PROSPERO # CRD42019080241.

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.

Relationship between rearfoot, tibia and femur kinematics in runners with and without patellofemoral pain

BACKGROUND

Patellofemoral pain (PFP) is the most common running overuse injury. Excessive rearfoot eversion is commonly considered as a PFP risk factor and the relationship between ankle-foot complex movement and lower limb may be involved with this dysfunction. The purpose of this study was to evaluate the correlation between rearfoot eversion with tibia and femur kinematics in frontal and transverse planes during running in individuals with and without PFP. The secondary purpose was to compare the lower limb kinematics between runners with and without PFP.

METHODS

Fifty-four recreational runners were divided into 2 groups: healthy runners (CG, n = 27) and runners with patellofemoral pain (PFPG, n = 27). Kinematics during running were assessed using three-dimensional motion analysis system. Pearson's correlation coefficients (r) were calculated to establish the correlation of rearfoot eversion with tibial and femur movements.

FINDINGS

Greater peak rearfoot eversion was correlated with greater peak femur adduction in PFP runners. Greater peak rearfoot eversion was correlated with greater peak tibial internal rotation and tibial adduction in the PFPG and CG. Additionally, greater peak rearfoot eversion was correlated with greater tibial internal rotation range of motion in the PFPG and CG. No significant differences were found between the PFPG and CG for all kinematics variables.

INTERPRETATION

Correlation between greater rearfoot eversion and greater peak hip adduction in the PFPG might be related to PFP persistence in runners with excessive rearfoot eversion, and indicates that treatment strategies aimed at controlling the movement of the rearfoot could help modify the symptoms.

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.

The relationship between rearfoot, tibial and hip kinematics in individuals with patellofemoral pain syndrome

BACKGROUND

Excessive rearfoot eversion is thought to be a risk factor for patellofemoral pain syndrome development, based on theoretical rationale linking it to greater tibial internal rotation and hip adduction. This study aimed to establish the relationship of rearfoot eversion with tibial internal rotation and hip adduction during walking in individuals with and without patellofemoral pain syndrome.

METHODS

Twenty-six individuals with patellofemoral pain syndrome and 20 controls (18-35years) participated. Each underwent instrumented three-dimensional motion analysis during over-ground walking. Pearson's correlation coefficients (r) were calculated to establish the relationship of rearfoot eversion with tibial internal rotation and hip adduction (peak and range of motion).

FINDINGS

Greater peak rearfoot eversion was associated with greater peak tibial internal rotation in the patellofemoral pain syndrome group (r=0.394, P=0.046). Greater rearfoot eversion range of motion was associated with greater hip adduction range of motion in the patellofemoral pain syndrome (r=0.573, P=0.002) and control (r=0.460, P=0.041) groups; and greater peak hip adduction in the control group (r=0.477, P=0.033).

INTERPRETATION

Associations between greater rearfoot eversion and greater hip adduction indicate that interventions targeted at the foot or hip in individuals with patellofemoral pain syndrome may have similar overall effects on lower limb motion and clinical outcomes. The relationship between rearfoot eversion and tibial internal rotation identified in the patellofemoral pain syndrome group may be related to aetiology. However, additional prospective research is needed to confirm this.

A self-adaptive foot-drop corrector using functional electrical stimulation (FES) modulated by tibialis anterior electromyography (EMG) dataset

We developed a functional electrical stimulator for correcting the gait patterns of patients with foot-drop problem. The stimulating electrical pulses of the system are modulated to evoke contractions of the tibialis anterior muscle, by emulating the normal patterns. The modulation is adaptive, i.e. the system can predict the user's step frequency and the generated stimulation can match each step in real-time. In this study, step data from 11 young healthy volunteers were acquired, and five prediction algorithms were evaluated by the acquired data, including the average of Previous N steps (P-N), the Previous Nth step (P-Nth), General Regression Neural Network (GRNN), Autoregressive (AR) and Kalman filter (KF). The algorithm with the best efficiency-accuracy trade-off (P-N, when N=5) was implemented in the FES system. System evaluation results obtained from a post-stroke patient with foot-drop showed that the system of this study demonstrated better performance on gait pattern correction than the methods widely adopted in commercial products.

Proximal and distal kinematics in female runners with patellofemoral pain

BACKGROUND

Female runners have a high incidence of developing patellofemoral pain. Abnormal mechanics are thought to be an important contributing factor to patellofemoral pain. However, the contribution of abnormal trunk, hip, and foot mechanics to the development of patellofemoral pain within this cohort remains elusive. Therefore the aim of this study was to determine if significant differences during running exist in hip, trunk and foot kinematics between females with and without patellofemoral pain.

METHODS

32 female runners (16 patellofemoral pain, 16 healthy control) participated in this study. All individuals underwent an instrumented gait analysis. Between-group comparisons were made for hip adduction, hip internal rotation, contra-lateral pelvic drop, contra-lateral trunk lean, rearfoot eversion, tibial internal rotation, as well as forefoot dorsiflexion and abduction

FINDINGS

The patellofemoral pain group had significantly greater peak hip adduction and hip internal rotation. No differences in contra-lateral pelvic drop were found. A trend towards reduced contra-lateral trunk lean was found in the patellofemoral pain group. No significant differences were found in any of the rearfoot or forefoot variables but significantly greater shank internal rotation was found in the patellofemoral pain group.

INTERPRETATION

We found greater hip adduction, hip internal rotation and shank internal rotation in female runners with patellofemoral pain. We also found less contra-lateral trunk lean in the patellofemoral pain group. This may be a potential compensatory mechanism for the poor hip control seen. Rehabilitation programs that correct abnormal hip and shank kinematics are warranted in this population.

Foot biomechanics and initial effects of infrapatellar strap on gait parameters in patients with unilateral patellofemoral pain syndrome

BACKGROUND

There is limited information on the relationship between plantar foot pressure and patellofemoral pain syndrome (PFPS). In addition, there is not enough research on the effects of an infrapatellar strap on PFPS.

OBJECTIVE

The aim of this study was to evaluate the immediate effects of an infrapatellar strap on dynamic pedabarography in patients with unilateral PFPS.

METHODS

Clinical case control study design. 18 females subjects with unilateral PFPS were included in the study. Gait parameters were tested using pedabarography during barefoot walking with and without an infrapatellar strap.

RESULTS

There were no statistically significant differences in gait trials comparing infrapatellar strap to no strap (P>0.05). In addition, a significant difference (P=0.043) in the % forefoot surface on the involved side demonstrated that body weight is transferred to medial aspect of the foot.

DISCUSSION

Although our results show a difference between the forefoot surface % of the affected and unaffected sides of subjects with PFPS there was no indication that an infrapatellar strap had any immediate effect on this parameter.

CONCLUSION

It is not clear whether PFPS is a cause or effect of abnormal gait. Further research is warranted to investigate the long-term effects of wearing an infrapatellar strap and associated altered foot biomechanics due to PFPS.

Relationships between the Foot Posture Index and foot kinematics during gait in individuals with and without patellofemoral pain syndrome

Background

Foot posture assessment is commonly undertaken in clinical practice for the evaluation of individuals with patellofemoral pain syndrome (PFPS), particularly when considering prescription of foot orthoses. However, the validity of static assessment to provide insight into dynamic function in individuals with PFPS is unclear. This study was designed to evaluate the extent to which a static foot posture measurement tool (the Foot Posture Index - FPI) can provide insight into kinematic variables associated with foot pronation during level walking in individuals with PFPS and asymptomatic controls.

Methods

Twenty-six individuals (5 males, 21 females) with PFPS aged 25.1 ± 4.6 years and 20 control participants (4 males, 16 females) aged 23.4 ± 2.3 years were recruited into the study. Each participant underwent clinical evaluation of the FPI and kinematic analysis of the rearfoot and forefoot during walking using a three-dimensional motion analysis system. The association of the FPI score with rearfoot eversion, forefoot dorsiflexion, and forefoot abduction kinematic variables (magnitude, timing of peak and range of motion) were evaluated using partial correlation coefficient statistics with gait velocity entered as a covariate.

Results

A more pronated foot type as measured by the FPI was associated with greater peak forefoot abduction (r = 0.502, p = 0.013) and earlier peak rearfoot eversion relative to the laboratory (r = -0.440, p = 0.031) in the PFPS group, and greater rearfoot eversion range of motion relative to the laboratory (r = 0.614, p = 0.009) in the control group.

Conclusion

In both individuals with and without PFPS, there was fair to moderate association between the FPI and some parameters of dynamic foot function. Inconsistent findings between the PFPS and control groups indicate that pathology may play a role in the relationship between static foot posture and dynamic function. The fair association between pronated foot posture as indicated by the FPI and earlier peak rearfoot eversion relative to the laboratory observed exclusively in those with PFPS is consistent with the biomechanical model of PFPS development. However, prospective studies are required to determine whether this relationship is causal.

Tempo de início da atividade elétrica dos estabilizadores patelares na marcha em sujeitos com e sem síndrome de dor femoropatelar

INTRODUÇÃO: A síndrome de dor femoropatelar (SDFP) é um problema comum que afeta uma em cada quatro pessoas. A alteração no tempo de ativação e a intensidade de contração dos músculos vasto medial oblíquo (VMO) e vasto lateral (VL) são consideradas fatores importantes na etiologia da SDFP. No entanto, existem poucos estudos sobre a função da porção oblíqua do vasto lateral (VLO) e nenhum sobre o tempo de ativação (onset) do VLO em atividades funcionais em sujeitos normais e com SDFP. OBJETIVO: Assim, o objetivo do estudo foi investigar o tempo de início de atividade eletromiográfica nos músculos VMO, VLO e VL longo (VLL) durante a marcha. MATERIAIS E MÉTODOS: A amostra foi formada por 15 sujeitos sem e 12 com SDFP. Dados eletromiográficos foram obtidos dos músculos VMO, VLL e VLO durante caminhada na esteira sem inclinação. A diferença relativa no onset (DRO) entre VMO-VLL e VMO-VLO foi determinada a partir da média de três passadas. RESULTADOS: Houve diferença entre os sujeitos com e sem SDFP em relação à DRO entre VMO-VLL. Nos sujeitos com SDFP, a ordem de início da atividade elétrica foi VLL seguida por VLO e após VMO. Nos indivíduos sem a patologia, a ordem foi diferente: primeiro VMO após VLO e, por último, VLL. CONCLUSÃO: Os achados sugerem que a ativação do VMO após o VLL poderia auxiliar no desenvolvimento e na manutenção da SDFP, enquanto o tempo de ativação do VLO possui menor participação.

Walking kinematics in individuals with patellofemoral pain syndrome: a case-control study

Patellofemoral pain syndrome (PFPS) development is considered to be multifactorial with various knee, hip and foot/ankle kinematic factors thought to be involved. A paucity of research evaluating kinematic factors throughout the lower limb kinematic chain simultaneously in individuals with PFPS was identified in a recent systematic review. The objective of this study was to compare kinematics at the knee, hip and foot/ankle in a group of individuals with PFPS to a group of asymptomatic controls. Twenty-six individuals with PFPS and 20 controls aged between 18 and 35 were recruited. Between-group comparisons were made for magnitude and timing of peak angles, and range of motion at the forefoot (dorsiflexion, abduction and supination), rearfoot (dorsiflexion, internal rotation and eversion), knee (flexion, abduction and internal rotation) and hip (adduction and internal rotation) during walking. The PFPS group demonstrated less peak hip internal rotation (7.0° versus 11.8°, p=0.024, p=0.024), earlier peak rearfoot eversion relative to the laboratory (30.4% versus 35.3% of the gait cycle, p=0.010) and tibia (32.7% versus 36.5% of the gait cycle, p=0.030), and greater rearfoot dorsiflexion range of motion relative to the laboratory (72.3° versus 68.2°, p=0.007). Additionally, a trend toward reduced gait velocity (p=0.070) was found in the PFPS group. Reduced peak hip internal rotation and gait velocity in individuals with PFPS may indicate compensation to reduce PFJ load during walking. However, earlier peak rearfoot eversion may be a factor related to the pathomechanical development of the condition.

The efficacy of foot orthoses in the treatment of individuals with patellofemoral pain syndrome: a systematic review

Patellofemoral pain syndrome (PFPS) is a highly prevalent condition, often reducing functional performance and being linked to osteoarthritis development later in life. Prescribing foot orthoses is often advocated, although the link between foot mechanics and PFPS development remains unclear. This systematic review was conducted to summarize and critique the existing evidence for the efficacy of foot orthoses in individuals with PFPS and to provide guidance for future research evaluating foot orthoses in individuals with PFPS. A comprehensive search of MEDLINE, EMBASE, CINAHL and Current Contents revealed 138 citations for review. Two of the authors independently reviewed and assessed each citation for inclusion and quality using a modified version of the quality assessment scale for randomized controlled trials in PFPS designed by Bizzini and colleagues. A total of seven studies were included in the final review. The review found limited evidence that prefabricated foot orthoses may reduce the range of transverse plane knee rotation and provide greater short-term improvements in individuals with PFPS compared with flat inserts. Findings also indicated that combining physiotherapy with prefabricated foot orthoses may be superior to prefabricated foot orthoses alone. Further research is now needed to establish the mechanisms behind the efficacy of foot orthoses and to identify individuals with PFPS who are most likely to benefit from prescription of foot orthoses. A comparison of the efficacy between prefabricated and customized foot orthoses is also needed.

Hallux valgus in patients with patellofemoral pain syndrome

The aim of this study was to investigate the presence of hallux valgus (HV) in patellofemoral pain syndrome (PFPS). Ninety-nine patients with unilateral patellofemoral pain participated. The study was designed with each subject acting as their own internal control by using the unaffected limb for comparison. The HV and intermetatarsal angles were measured by weight-bearing anteroposterior radiographs in patients. Eighty-four out of 99 patients had an abnormal HV angle on the affected side and 78 of 99 patients had an abnormal HV angle on the unaffected side. There were significant differences in the HV angle between affected and unaffected sides (P = 0.003). This study is the first to demonstrate the relationship between HV and PFPS. Further comprehensive biomechanical studies are warranted to analyse the relationship between HV and PFPS.

Kinematic gait characteristics associated with patellofemoral pain syndrome: a systematic review

Development of patellofemoral pain syndrome (PFPS) is considered to be multifactorial. The aims of this systematic review were to (i) summarise and critique the body of literature addressing kinematic gait characteristics associated with PFPS; and (ii) provide recommendations for future research addressing kinematic gait characteristics associated with PFPS. A comprehensive search of MEDLINE, EMBASE, CINAHL, and Current Contents revealed 561 citations for review. Each citation was assessed for inclusion and quality using a modified version of the 'Quality Index' and a novel inclusion/exclusion criteria checklist by two independent reviewers. A total of 24 studies were identified. No prospective studies with adequate data to complete effect size calculations were found. Quality of included case-control studies varied, with a number of methodological issues identified. Heterogeneity between studies made meta-analysis inappropriate. Reductions in gait velocity were indicated during walking, ramp negotiation, and stair negotiation in individuals with PFPS. Findings indicated delayed timing of peak rearfoot eversion and increased rearfoot eversion at heel strike transient during walking; and delayed timing of peak rearfoot eversion, increased rearfoot eversion at heel strike, reduced rearfoot eversion range, greater knee external rotation at peak knee extension moment, and greater hip adduction during running in individuals with PFPS. There is a clear need for prospective evaluation of kinematic gait characteristics in a PFPS population to distinguish between cause and effect. Where possible, future PFPS case-control studies should consider evaluating kinematics of the knee, hip and foot/ankle simultaneously with larger participant numbers. Completing between sex comparisons when practical and considering spatiotemporal gait characteristics during methodological design and data analysis is also recommended.

Automatic recognition of gait patterns exhibiting patellofemoral pain syndrome using a support vector machine approach

Patellofemoral pain syndrome (PFPS) is a common disorder that afflicts people across all age groups, and results in various degrees of knee pain. The diagnosis of PFPS is difficult since the exact biomechanical factors and the extent to which they are affected by the disorder are still unknown. Recent research has reported significant statistical differences in ground reaction forces (GRFs) and foot kinematics, which could be indicative of PFPS, but the interrelationship between many of these measures and the pathology have been absent so far. In this paper, we applied the support vector machines (SVMs) to detect PFPS gait based on 14 GRF and 16 foot kinematic features recorded from 27 subjects (14 healthy and 13 with PFPS). The influence of combined gait parameters on classification performance was investigated through the use of a feature-selection algorithm. The optimal feature set was then compared against the most statistically significant individual features (p < 0.05) found by previous study. Test results indicated that GRF features alone resulted in a higher leave-one-out (LOO) classification accuracy (85.15%) compared to 74.07% using only kinematic features. A hill-climbing feature-selection algorithm was applied to determine the subset of combined kinematic and kinetic features, which provided optimal classifier performance. This subset, which consists of six features (two from GRF and four from foot kinematic features), provided an improved LOO accuracy of 88.89% . The optimal feature set detected by the SVM, which best identified gait characteristics of PFPS, was found to be closely related to inferential statistical analysis with the added distinction that the SVM could potentially be deployed as an automated system for detecting gait changes in patients with PFPS.

The influence of gluteus maximus on transverse plane tibial rotation

There is a common clinical belief that transverse plane tibial rotation is controlled by the rearfoot. Although distal structures may influence the motion of the tibia, transverse plane tibial rotation could be determined by the proximal hip musculature. Cadaver studies have identified gluteus maximus as having the largest capacity for external rotation of the hip. This study was therefore undertaken to investigate the effect of gluteus maximus on tibial motion. Kinematic data were collected from the foot and tibia along with EMG data from gluteus maximus for 17 male subjects during normal walking. A number of kinematic parameters were derived to characterise early stance phase. Gluteus maximus function was characterised using RMS EMG and EMG on/off times. No differences in muscle timing were found to be associated with any of the kinematic parameters. In addition, no differences in gluteal activation levels were found between groups of subjects who had different amounts of tibial rotation. However, there was a significant difference (p<0.001) in gluteus maximus activation when groups were defined by the time taken to decelerate the tibia (time to peak internal velocity). Specifically, subjects with greater gluteus maximus activity had a lower time to decelerate the tibia. We suggest that a high level of gluteus maximus activity results in a larger external torque being applied to the femur, which ultimately leads to a more rapid deceleration of the tibia.

A prospective study on gait-related intrinsic risk factors for patellofemoral pain

OBJECTIVE

To prospectively determine gait-related risk factors for patellofemoral pain.

DESIGN

A prospective cohort study.

SETTING

Male and female recruits of the Belgian Royal Military Academy during a 6-week basic military training period.

PARTICIPANTS

Eighty-four officer cadets (65 men, 19 women), who entered the Military Academy and were without a history of any knee or lower-leg complaints, participated in the study.

INTERVENTIONS

Before the start of the 6-week basic military training period, plantar pressure measurements during walking were performed. During the basic military training period, patellofemoral complaints were diagnosed and registered by a sports medicine physician.

MAIN OUTCOME MEASUREMENTS

Plantar pressure measurements during walking were performed using a footscan pressure plate (RsScan International).

RESULTS

During the 6-week training period, 36 subjects developed patellofemoral pain (25 male and 11 female). Logistic regression analysis revealed that subjects who developed patellofemoral pain had a significantly more laterally directed pressure distribution at initial contact of the foot, a significantly shorter time to maximal pressure on the fourth metatarsal, and a significantly slower maximal velocity of the change in lateromedial direction of the center of pressure during the forefoot contact phase.

CONCLUSIONS

Our findings suggest that the feet of the persons who developed anterior knee pain have a heel strike in a less pronated position and roll over more on the lateral side compared with the control group. The results of this study can be considered valuable in identifying persons at risk for patellofemoral pain.

Tibia and rearfoot motion and ground reaction forces in subjects with patellofemoral pain syndrome during walking

Abnormal subtalar joint function and the consequent rotation of the tibia during walking are thought to contribute to patellofemoral pain syndrome (PFPS). The purpose of this study was to measure rearfoot and tibia motion, and the ground reaction force (GRF) during the stance phase of walking in subjects with PFPS and compare them to healthy subjects. A four camera motion analysis system with a single force plate was used to investigate rearfoot motion relative to the tibia in three planes, the tibial transverse plane rotation and the GRF during the stance phase of walking in 13 female subjects diagnosed with PFPS and 14 healthy females. Analysis showed significantly delayed peak rearfoot eversion (p=0.02), and earlier occurrence of peak dorsiflexion (p=0.02) for the PFPS group. Furthermore, significantly lower peak medial GRF (p=0.03), minimum vertical GRF trough (p=0.02) and the second vertical GRF peak (p=0.01) were found in the PFPS group. Tibial transverse rotation was not shown to be different in PFPS subjects. However, there was prolonged rearfoot eversion during the stance phase of walking. The earlier appearance of rearfoot dorsiflexion as well as the lower GRFs indicate altered propulsive function of the foot during supination.

Electric muscle stimulation of the quadriceps in the treatment of patellofemoral pain

OBJECTIVE

To compare a commercially available electric muscle stimulation regimen with a novel form of stimulation for the rehabilitation of the quadriceps muscle, in patients with patellofemoral pain syndrome.

DESIGN

Double-blinded randomized trial with a parallel control group and stratified randomization.

SETTING

Home-based rehabilitation program assessed in research center.

PARTICIPANTS

Eighty patients (47 women, 33 men) with patellofemoral pain syndrome.

INTERVENTIONS

One group (EMPI) received 1 uniform constant frequency component of 35Hz. The other (EXPER) group received an experimental form of stimulation that contained 5 simultaneously delivered frequency components of 125, 83, 50, 2.5, and 2Hz. Stimulation was applied to the quadriceps muscles of the affected leg for 1 hour daily for 6 weeks, a total of 42 treatments.

MAIN OUTCOME MEASURES

Lower-limb isometric and isokinetic torque, quadriceps fatigue, knee flexion, patellar pain, a step test, quadriceps cross-sectional area, and Kujala patellofemoral score for pain before and after treatment.

RESULTS

Seventy-four patients (43 women, 31 men) completed the trial. Patients in both groups showed significant improvements in all outcomes (P<.05). No significant differences existed between the 2 stimulators in any outcome (P>.05) except for quadriceps cross-sectional area (P=.023).

CONCLUSIONS

One form of stimulation was just as efficacious as the other in improving subjective and objective measures.

Quantification of patellofemoral joint contact area using magnetic resonance imaging

To describe a method for quantifying patellofemoral joint contact area using magnetic resonance imaging (MRI), we used a repeated measures design using cadaver specimens. The use of contact area obtained from cadaveric specimens for biomechanical modeling does not permit investigators to assess the inter-subject variability in contact area as a result of patellofemoral pathology or malalignment. Therefore, a method for measuring patellofemoral joint contact area in-vivo is necessary. Six fresh frozen unmatched human cadaver knees were thawed at room temperature and minimally dissected to permit insertion of a pressure sensitive film packet into the suprapatellar pouch. A custom loading apparatus was designed to apply a compressive load to the patellofemoral joint at 30 degrees of flexion. Simultaneous measurement of contact area was made using both the pressure sensitive film technique and MRI. The intraclass correlation coefficient (ICC) and coefficient of variation were used to compare the agreement between the two methods and to assess the repeatability of the MRI method. Good agreement was found between the MRI and pressure sensitive film techniques (ICC 0.91; CV 13%). The MRI technique also was found to be highly reproducible (ICC 0.98; CV 2.3%). MRI assessment of patellofemoral joint contact area was found to be comparable to the established pressure sensitive film technique. These results suggest that this method may be a valuable tool in quantifying patellofemoral joint contact area in-vivo. Quantification of the patellofemoral joint stress has been dependent on patellofemoral joint contact area obtained from cadaver specimens, thereby negating the potential influence of subject specific variability. Developing a non-invasive technique to evaluate contact area will assist researchers and/or clinicians in obtaining patient-specific contact area data to be used in biomechanical analyses and clinical decision making.

Patellofemoral stress during walking in persons with and without patellofemoral pain

OBJECTIVE

To determine whether individuals with patellofemoral pain (PFP) demonstrate elevated patellofemoral joint (PFJ) stress compared with pain-free controls during free and fast walking.

DESIGN

A cross-sectional study utilizing an experimental and a control group.

BACKGROUND

Although the cause of PFJ pathology is believed to be related to elevated joint stress (force per unit area), this hypothesis has not been adequately tested and causative mechanisms have not been clearly defined.

METHODS

Ten subjects with a diagnosis of PFP and 10 subjects without pain participated. All subjects completed two phases of data collection: 1) magnetic resonance imaging (MRI) assessment to determine PFJ contact area and 2) comprehensive gait analysis during self-selected free and fast walking velocities. Data obtained from both phases were required as input variables into a biomechanical model to quantify PFJ stress.

RESULTS

On the average, PFJ stress was significantly greater in subjects with PFP compared with control subjects during level walking. The observed increase in PFJ stress in the PFP group was attributed to a significant reduction in PFJ contact area, as the PFJ reaction forces were similar between groups.

CONCLUSION

Our results are consistent with the hypothesis that increased patellofemoral joint stress may be a predisposing factor with respect to development of PFP. Clinically, these findings indicate that treatments designed to increase the area of contact between the patella and the femur may be beneficial in reducing the PFJ stress during functional activities.

RELEVANCE

Patellofemoral pain affects about 25% of the population, yet its etiology is unknown. Knowledge of the biomechanical factors contributing to patellofemoral joint pain may improve treatment techniques and guide development of prevention strategies.

A comparison of two types of electrical stimulation of the quadriceps in the treatment of patellofemoral pain syndrome. A pilot study

OBJECTIVE

To compare a commercially available electrical muscle stimulation regime with a new form of stimulation for the rehabilitation of the quadriceps in patients with patellofemoral pain syndrome.

SETTING

A research facility within a teaching hospital.

METHODS

Sixteen patients (four men, 12 women) with patellofemoral pain, demonstrable quadriceps atrophy, but normal gait parameters were randomly allocated to one of two treatment groups. One group received a sequential mixed frequency stimulation pattern from a standard device. The other group received a new form of stimulation from an experimental stimulation device that contained simultaneous mixed frequency components.

OUTCOME MEASURES

Isometric and isokinetic extension torque, muscle fatigue rate, pain, functional questionnaire, step test, knee flexion, and quadriceps cross-sectional area.

RESULTS

These showed significant improvements for both groups after treatment (p < 0.05) in all outcome measures except flexion and fatigue rates, but no significant differences between the two stimulation regimes (p > 0.05).

CONCLUSION

Both stimulators performed similarly on patients with patellofemoral pain giving significant improvements for all patients for muscle strength, pain, self-reporting function and step testing. There were no significant differences between the two types of stimulation.

Electromyographic fatigue characteristics of the quadriceps in patellofemoral pain syndrome

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

Asymmetry of gait initiation in patients with unilateral knee arthritis

OBJECTIVE

To identify how patients with knee arthritis modify their equilibrium and movement control strategies during gait initiation.

DESIGN

Observational study.

SETTING

University hospital movement analysis laboratory.

PARTICIPANTS

Twelve patients with unilateral knee arthritis and 12 healthy control subjects.

MAIN OUTCOME MEASURES

Durations of the phases of gait initiation (ie, postural, monopodal, and double-support phases), center-of-pressure displacements, ground reaction forces, pelvic velocity, step length, and knee range of motion were measured using a movement analysis system and force plates.

RESULTS

Gait initiation was slower in patients than in controls no matter which leg was the supporting one. In patients, the durations of the postural and the monopodal phases were modified in an asymmetrical way according to the leg used as the supporting one. The postural phase was lengthened and the monopodal phase was shortened when the affected leg was the supporting one. Opposite effects were observed when the sound leg was supporting. Step length, knee range of motion, and maximal pelvic velocity were reduced in patients whatever the side of the supporting leg.

CONCLUSION

Gait initiation is an asymmetrical process in unilateral knee arthritis patients, who develop adaptive posturomotor strategies that shorten the monopodal phase on the affected leg.