Indeed, Correlation Does Not Indicate Causation!

Author response to the JOSPT Letter to the Editor-in-Chief "Lower-Limb Kinematics and Clinical Outcomes: Correlation Does not Imply Causality" J Orthop Sports Phys Ther 2023;53(11):723-725. doi:10.2519/jospt.2023.0203-R.

Are Changes in Dynamic Knee Movement Control Related to Changes in Pain or Function in People With Knee Disorders? A Systematic Review and Meta-analysis.

OBJECTIVE: To study whether changes in dynamic knee valgus or varus were associated with changes in pain or function in people with knee disorders. DESIGN: Systematic review with meta-analysis. LITERATURE SEARCH: We searched the MEDLINE, Embase, CINAHL, SPORTDiscus, Cochrane Library, and Web of Science, from inception up to January 2023. STUDY SELECTION CRITERIA: We included randomized controlled trials investigating the effects of nonsurgical (including nonpharmacological) interventions for knee disorders on frontal and transverse plane knee and hip movements during functional tasks, which reported pain and/or function outcomes. DATA SYNTHESIS: The relationship between changes in kinematics and pain/function was analyzed using a 2-stage structural equation modeling approach. RESULTS: From 42 202 records, 48 trials met the eligibility criteria. For people with patellofemoral pain (25 trials, n = 894), there was moderate evidence that changes in the knee and hip movements were significantly correlated with changes in pain and function (r= -0.69 to 0.73), except for the knee transverse plane movements and for the relationship between hip transverse plane movement and function. For people with knee osteoarthritis (15 trials, n = 704) and anterior cruciate ligament injuries (8 trials, n = 198), the evidence was limited and uncertain. CONCLUSION: The relationship between changes in movement control and clinical outcomes was consistent in people with patellofemoral pain. For people with knee osteoarthritis or anterior cruciate ligament injuries, there was a paucity of evidence that precluded a proper evaluation of the relationship between dynamic knee movement control, and pain and function. J Orthop Sports Phys Ther 2023;53(7):1-14. Epub: 18 April 2023. doi:10.2519/jospt.2023.11628.

The relationship between urinary C-Telopeptide fragments of type II collagen, knee joint load, pain, and physical function in individuals with medial knee osteoarthritis.

OBJECTIVE: Considering the osteoarthritis (OA) model that integrates the biological, mechanical, and structural components of the disease, the present study aimed to investigate the association between urinary C-Telopeptide fragments of type II collagen (uCTX-II), knee joint moments, pain, and physical function in individuals with medial knee OA. METHODS: Twenty-five subjects radiographically diagnosed with knee OA were recruited. Participants were evaluated through three-dimensional gait analysis, uCTX-II level, the WOMAC pain and physical function scores, and the 40m walk test. The association between these variables was investigated using Pearson's product-moment correlation, followed by a hierarchical linear regression, controlled by OA severity and body mass index (BMI). RESULTS: No relationship was found between uCTX-II level and knee moments. A significant correlation between uCTX-II level and pain, physical function, and the 40m walk test was found. The hierarchical linear regression controlling for OA severity and BMI showed that uCTX-II level explained 9% of the WOMAC pain score, 27% of the WOMAC physical function score, and 7% of the 40m walk test. CONCLUSION: Greater uCTX-II level is associated with higher pain and reduced physical function and 40m walk test performance in individuals with medial knee OA.

Translation, adaptation and validation of the Nurse-Work Instability Scale to Brazilian Portuguese. / Tradução, adaptação e validação da Escala de Instabilidade no Trabalho de Enfermagem para português brasileiro.

OBJECTIVE: to translate, adapt and test the psychometric properties of the Brazilian Nurse-Work Instability Scale. METHOD: this was a methodological study following the translation steps: synthesis, back-translation, specialist´s committee, semantics analysis, pretest, and psychometric tests. The committee was composed of 5 specialists. For the semantics analysis, 18 nursing workers evaluated the instrument and 30 pretested it. For the psychometric tests, the sample size was 214 nursing workers. The internal construct validity was analyzed by the Rasch model. Reliability was assessed using internal consistency, and concurrent validity with Pearson's correlation between the Nurse-Work Instability Scale, and the Work Ability Index, Job Stress Scale. RESULTS: a Nurse-Work Instability Scale in Brazilian Portuguese with 20 items showed an adequate reliability (0.831), stability (p <0.0001), and an expected correlation with Work Ability Index (r = -0.526; P<0.0001) and Job Stress Scale (r = 0.352; p <0.0001). CONCLUSION: the instrument is appropriated to detect work instability in Brazilian nursing workers with musculoskeletal disorders. Its application is fundamental to avoid long-term withdrawal from work by early identification of the work instability. Furthermore, the scale can assist the development of actions and strategies to prevent the abandonment of the profession of nursing workers affected by musculoskeletal disorders.

The role of hip abductor strength on the frontal plane of gait in subjects with medial knee osteoarthritis.

OBJECTIVE: This study aimed to investigate the relationship of hip abductor strength with external hip and knee adduction moments, pain and physical function, and trunk, pelvis, and hip kinematics in the frontal plane during walking in subjects with medial knee osteoarthritis. METHODS: Twenty-five subjects with medial knee osteoarthritis were evaluated through an isokinetic strength test for hip abductor, three-dimensional gait analysis (kinetics and kinematics), and pain and physical function scores. Regression models were used to control the influence of other parameters such as pain, age, gender, severity, walking speed, mass, and height. RESULTS: No relationship was found of hip abductor strength with peak of external knee adduction moment and knee adduction angular impulse. Hip abductor strength explained 17% of contralateral pelvic drop and 21% of hip adduction angle. In addition, hip abductor strength explained 4% and 1% of the variance in the WOMAC physical function score and 40-m fast paced walk test, respectively. CONCLUSION: Considering the relationship of hip abductor strength with contralateral pelvic drop and hip adduction angle, specific exercises might improve physical function and lower limb dynamic alignment during gait.

Cryotherapy reduces muscle hypertonia, but does not affect lower limb strength or gait kinematics post-stroke: a randomized controlled crossover study.

BACKGROUND: Based on the premise that spasticity might affect gait post-stroke, cryotherapy is among the techniques used to temporarily reduce spasticity in neurological patients. This effective technique would enhance muscle performance, and ultimately, functional training, such as walking. However, understanding whether a decrease in spasticity level, if any, would lead to improving muscle performance and gait parameters is not based on evidence and needs to be clarified. OBJECTIVES: to investigate the immediate effects of cryotherapy, applied to spastic plantarflexor muscles of subjects post-stroke, on tonus level, torque generation capacity of plantarflexors and dorsiflexors, and angular/spatiotemporal gait parameters. METHODS: Sixteen chronic hemiparetic subjects participated in this randomized controlled crossover study. Cryotherapy (ice pack) or Control (room temperature sand pack) were applied to the calf muscles of the paretic limb. The measurements taken (before and immediately after intervention) were: 1) Tonus according to the Modified Ashworth Scale; 2) Torque assessments were performed using an isokinetic dynamometer; and 3) Spatiotemporal and angular kinematics of the hip, knee, and ankle (flexion/extension), obtained using a tridimensional movement analysis system (Qualisys). RESULTS: Cryotherapy decreased plantarflexor tonus but did not change muscle torque generation capacity and did not affect spatiotemporal or angular parameters during gait compared to control application. These findings contribute to the evidence-based approach to clinical rehabilitation post-stroke. CONCLUSIONS: The findings of this study suggest that cryotherapy applied to the calf muscles of subjects with chronic hemiparesis reduces muscle hypertonia but does not improve dorsiflexors and plantarflexors performance and gait parameters.

Performance of Different Timed Up and Go Subtasks in Frailty Syndrome.

BACKGROUND AND PURPOSE: Gait speed, mobility, and postural transitions should be taken into account in older adults with frailty syndrome and can be assessed by the Timed Up and Go (TUG) Test. However, it is unclear which TUG subtasks have greater influence in identifying frail people and whether prefrail individuals present with any reduced subtask performance. The objective of this study was to investigate the differences in performance of TUG subtasks between frail, prefrail, and nonfrail older adults. METHODS: A cross-sectional study was performed with community-dwelling older adults, including 43 nonfrail, 30 prefrail, and 7 frail individuals. The TUG subtasks (sit-to-stand, walking forward, turning, walking back, and turn-to-sit) were assessed using a Qualisys motion system. Data were captured by Qualisys Track Manager software and processed by Visual 3D software. The Matlab program was used to detect, separate, and analyze the TUG subtasks. Statistical significance was set at α= .05 and SigmaPlot software (11.0) was used. RESULTS AND DISCUSSION: The total time to complete the TUG was significantly longer among frail participants than among those who were prefrail and nonfrail. Statistically significant differences in temporal parameters in the turning, walking forward, and walking back subtasks between nonfrail/prefrail and frail older people were found. In addition, the transition TUG subtasks (average and peak velocities of the trunk) distinguished the frail group from the other groups, demonstrating altered quality of movement. CONCLUSIONS: The findings support the value of analyzing the TUG subtasks to improve understanding of mobility deficits in frailty syndrome.

Patellofemoral joint stress measured across three different running techniques.

BACKGROUND: Patellofemoral pain (PFP) is the most common running-related injury. It has been shown in previous studies that gait retraining may have a beneficial effect on patellofemoral joint stress (PFJS). RESEARCH QUESTION: Is there a reduction of PFJS across 4 running conditions: 1. runner's typical rearfoot strike pattern, 2. forefoot landing, 3. step rate increase by 10% and 4. forward trunk lean? METHODS: Nineteen healthy runners (28.05 ± 5.03 years; 26.58 ± 8.85 km/week, 6.00 ± 4.51 years of running experience) completed one running trial for each condition, at the same subject-specific comfortable speed on a treadmill. Kinetic and kinematic data were collected and measures of hip, knee and ankle joint moments and PFJS were calculated. RESULTS: Compared to rearfoot strike condition, peak PFJS and PFJS-time integral per step were significantly (P < 0.01) lower during forefoot landing and step rate increase conditions. PFJS per kilometer was significantly reduced for forefoot landing (17.01%; P < 0.01) and increased step rate (12.90%; P = 0.003). Forward trunk lean technique showed no significant differences in peak PFJS (P = 0.187), PFJS-time integral per step (P = 0.815) and PFJS per kilometer (P = 0.077) compared to rearfoot strike pattern. INTERPRETATION: The comparison between techniques revealed greater reductions on PFJS by forefoot landing, followed by 10% step rate increase condition. These changes were the result of different lower limb movement strategies across the 2 running conditions. We conclude that compared to a rearfoot strike pattern, both a forefoot landing and step rate increase result in lower cumulative PFJS joint stress in healthy runners, with the forefoot landing being the most effective. These running technique modifications could be recommended to reduce PFJS loads and may have implications for PFP prevention.

Differences in Timed Up and Go Subtasks Between Older People With Mild Cognitive Impairment and Mild Alzheimer's Disease.

This study compared performances of timed up and go test subtasks between 40 older people with preserved cognition, 40 with mild cognitive impairment, and 38 with mild Alzheimer's disease. The assessment consisted of anamneses and timed up and go test subtasks (sit-to-stand, walking forward, turn, walking back, and turn-to-sit). Data were captured by Qualisys Track Manager software and processed by Visual3D software. The MATLAB program was applied to detect and analyze timed up and go test subtasks. All subtasks differentiated people with Alzheimer's disease and preserved cognition, except the sit-to-stand subtask, which did not distinguish any group. The walking forward subtask differed older people with preserved cognition from mild cognitive impairment, specifically on minimum peak of knee, average value of knee, and hip (pitch axis) during stance phase. The walking back, turn, and turn-to-sit subtasks distinguished subjects with Alzheimer's disease from mild cognitive impairment. The separated analysis of transition and walking subtasks is important in identifying mobility patterns among cognitive profiles.

Tradução, adaptação e validação da Escala de Instabilidade no Trabalho de Enfermagem para português brasileiro / Translation, adaptation and validation of the Nurse-Work Instability Scale to Brazilian Portuguese / Traducción, adaptación y validación de la Escala de Inestabilidad en el Trabajo de Enfermería para el Portugués de Brasil

Objetivo traduzir, adaptar e testar as propriedades psicométricas da Nurse-Work Instability Scale (Escala de Instabilidade no Trabalho de Enfermagem) em português do Brasil. Método trata-se de um estudo metodológico seguindo os passos de tradução: síntese, retrotradução, comitê de especialistas, análise semântica, pré-teste e testes psicométricos. O comitê foi composto por 5 especialistas. Para a análise semântica, 18 profissionais de enfermagem avaliaram o instrumento e 30 fizeram o pré-teste. Para os testes psicométricos, o tamanho da amostra foi de 214 profissionais de enfermagem. A validade interna do construto foi analisada pelo modelo de Rasch. A confiabilidade foi avaliada usando consistência interna e validade concorrente com a correlação de Pearson entre a Nurse-Work Instability Scale, o Work Ability Index (Índice de Capacidade para o Trabalho) e a Job Stress Scale (Escala de Estresse no Trabalho). Resultados a Nurse-Work Instability Scale com 20 itens em português brasileiro apresentou confiabilidade (0,831), estabilidade (p <0,0001) e correlação esperada adequadas com o Work Ability Index (r = -0,526; P 0,0001) e a Job Stress Scale (r = 0,352; p 0,0001). Conclusão o instrumento é apropriado para detectar a instabilidade do trabalho em profissionais de enfermagem brasileiros com distúrbios osteomusculares. Sua aplicação é fundamental para evitar o afastamento do trabalho a longo prazo pela identificação precoce da instabilidade do trabalho. Além disso, a escala pode auxiliar no desenvolvimento de ações e estratégias para prevenir que profissionais de enfermagem acometidos por distúrbios osteomusculares abandonem a profissão.

Objective to translate, adapt and test the psychometric properties of the Brazilian Nurse-Work Instability Scale. Method this was a methodological study following the translation steps: synthesis, back-translation, specialist´s committee, semantics analysis, pretest, and psychometric tests. The committee was composed of 5 specialists. For the semantics analysis, 18 nursing workers evaluated the instrument and 30 pretested it. For the psychometric tests, the sample size was 214 nursing workers. The internal construct validity was analyzed by the Rasch model. Reliability was assessed using internal consistency, and concurrent validity with Pearson's correlation between the Nurse-Work Instability Scale, and the Work Ability Index, Job Stress Scale. Results a Nurse-Work Instability Scale in Brazilian Portuguese with 20 items showed an adequate reliability (0.831), stability (p <0.0001), and an expected correlation with Work Ability Index (r = -0.526; P<0.0001) and Job Stress Scale (r = 0.352; p <0.0001). Conclusion the instrument is appropriated to detect work instability in Brazilian nursing workers with musculoskeletal disorders. Its application is fundamental to avoid long-term withdrawal from work by early identification of the work instability. Furthermore, the scale can assist the development of actions and strategies to prevent the abandonment of the profession of nursing workers affected by musculoskeletal disorders.

Objetivo traducir, adaptar y probar las propiedades psicométricas del Escala Brasileña de Inestabilidad en el Trabajo de Enfermería. Método ha sido un estudio metodológico en la secuencia de las etapas de la traducción: la síntesis, la retrotraducción, el comité de expertos, el análisis semántico, la prueba previa y las pruebas psicométricas. El comité ha sido conformado por 5 expertos. Para el análisis semántico, 18 trabajadores han evaluado el instrumento y 30 han sido probados previamente. Para las pruebas psicométricas, el tamaño del muestreo ha sido de 214 trabajadores de enfermería. La validez del constructo interno ha sido analizada por el modelo de Rasch. La confiabilidad ha sido evaluada por medio de la consistencia interna, y la validez competente con la correlación de Pearson entre la Escala de Inestabilidad en el Trabajo de Enfermería, y el Índice de Capacidad de Trabajo, Escala de Estrés en el Trabajo. Resultados una Escala de Inestabilidad en el Trabajo de Enfermería Portugués con 20 ítems ha mostrado una confiabilidad adecuada (0.831), estabilidad (p <0.0001), y una correlación que ha sido esperada con el Índice de Capacidad de Trabajo (r = -0.526; P<0.0001) y la Escala de Estrés en el Trabajo (r = 0.352; p <0.0001). Conclusión el instrumento es apropiado para detectar la instabilidad del trabajo en trabajadores Brasileños con disturbios musculo esqueléticos. Su aplicación es fundamental para evitar el abandono de largo plazo del trabajo por la identificación temprana de la instabilidad del trabajo. Además de eso, la escala puede ayudar en el desarrollo de acciones y estrategias para prevenir el abandono de la profesión de trabajadores de enfermería que han sido afectados por el disturbio musculo esquelético.

Core stability, shoulder peak torque and function in throwing athletes with and without shoulder pain.

OBJECTIVE: This study compared core stability, shoulder isokinetic peak torque and shoulder function in throwers with and without shoulder pain. DESIGN: Cross-sectional study. SETTINGS: Throwing athletes. PARTICIPANTS: Thirty healthy athletes and 21 with shoulder pain were included. MAIN OUTCOME MEASURES: Endurance time of the trunk, the modified star excursion balance test, isokinetic peak torque of internal and external rotation of the shoulder, questionnaires, level of satisfaction with the throwing arm and active range of motion. RESULTS: The symptomatic athletes presented with shorter endurance time for the trunk lateral flexors (P < .05), and decreased reach distance for both limbs in the posteromedial direction (P < .05) and for takeoff limb in the posterolateral direction (P = .04), and smaller composite score for both limbs (P < .05) during star excursion balance test as compared to the healthy ones. No significant differences between groups were found for peak torque of internal and external rotation of the shoulder. Athletes with shoulder pain demonstrated more shoulder disability and a lower level of satisfaction with the throwing arm (P = .000). Range of motion was not different between groups for shoulder internal and external rotation. CONCLUSION: Throwing athletes with shoulder pain have lower core stability and shoulder function compared to healthy athletes.

Performances on the Timed Up and Go Test and subtasks between fallers and non-fallers in older adults with cognitive impairment.

This work aimed to compare performances on the Timed Up and Go (TUG) test and its subtasks between faller and non-faller older adults with mild cognitive impairment (MCI) and mild Alzheimer's disease (AD). A prospective study was conducted, with 38 older adults with MCI and 37 with mild AD. Participants underwent an assessment at baseline (the TUG and its subtasks using the Qualisys ProReflex system) and the monitoring of falls at the six-month follow up. After six months, 52.6% participants with MCI and 51.3% with AD fell. In accordance with specific subtasks, total performance on the TUG distinguished fallers from non-fallers with AD, fallers from non-fallers with MCI and non-fallers with MCI from non-fallers with AD. Although no other difference was found in total performances, non-fallers with MCI and fallers with AD differed on the walking forward, turn and turn-to-sit subtasks; and fallers with MCI and non-fallers with AD differed on the turn-to-sit subtask.

Performances on the Timed Up and Go Test and subtasks between fallers and non-fallers in older adults with cognitive impairment / Performances no teste Timed Up and Go e subtarefas em idosos com comprometimento cognitivo, caidores e não caidores

ABSTRACT This work aimed to compare performances on the Timed Up and Go (TUG) test and its subtasks between faller and non-faller older adults with mild cognitive impairment (MCI) and mild Alzheimer's disease (AD). A prospective study was conducted, with 38 older adults with MCI and 37 with mild AD. Participants underwent an assessment at baseline (the TUG and its subtasks using the Qualisys ProReflex system) and the monitoring of falls at the six-month follow up. After six months, 52.6% participants with MCI and 51.3% with AD fell. In accordance with specific subtasks, total performance on the TUG distinguished fallers from non-fallers with AD, fallers from non-fallers with MCI and non-fallers with MCI from non-fallers with AD. Although no other difference was found in total performances, non-fallers with MCI and fallers with AD differed on the walking forward, turn and turn-to-sit subtasks; and fallers with MCI and non-fallers with AD differed on the turn-to-sit subtask.

RESUMO O objetivo deste trabalho foi comparar o desempenho do Timed up and go test (TUG) e suas subtarefas entre idosos caidores e não caidores com comprometimento cognitivo leve (CCL) e doença de Alzheimer (DA) leve. Um estudo prospectivo foi conduzido, com 38 idosos com CCL e 37 com DA leve. Foi realizada uma avaliação inicial (TUG e subtarefas por meio do sistema Qualisys Pro Reflex) e um monitoramento de quedas por 6 meses. Após 6 meses, 52.6% pessoas com CCL e 51.3% com DA caíram. Em concordância com subtarefas específicas, a performance total do TUG distinguiu caidores de não caidores com DA, caidores de não caidores com CCL e não caidores com CCL de não caidores com DA. Embora nenhuma outra diferença foi encontrada na performance total do TUG, não caidores com CCL e caidores com DA apresentaram diferenças nas performances das subtarefas marcha ida, retornar e virar-se para sentar; e caidores com CCL e não caidores com DA diferiram na subtarefa virar-se para sentar.

Inter- and intra-rater reliability of 3D kinematics during maximum mouth opening of asymptomatic subjects.

Previous studies evaluated 3D human jaw movements using kinematic analysis systems during mouth opening, but information on the reliability of such measurements is still scarce. The purpose of this study was to analyze within- and between-session reliabilities, inter-rater reliability, standard error of measurement (SEM), minimum detectable change (MDC) and consistency of agreement across raters and sessions of 3D kinematic variables during maximum mouth opening (MMO). Thirty-six asymptomatic subjects from both genders were evaluated on two different days, five to seven days apart. Subjects performed three MMO movements while kinematic data were collected. Intraclass correlation coefficient (ICC), SEM and MDC were calculated for all variables, and Bland-Altman plots were constructed. Jaw radius and width were the most reproducible variables (ICC>0.81) and demonstrated minor error. Incisor displacement during MMO and angular movements in the sagittal plane presented good reliability (ICC from 0.61 to 0.8) and small errors and, consequently, could be used in future studies with the same methodology and population. The variables with smaller amplitudes (condylar translations during mouth opening and closing and mandibular movements on the frontal and transversal planes) were less reliable (ICC<0.61) and presented larger SEM and MDC. Although ICC, SEM and MDC showed less between-session reproducibility than within-session and inter-rater, the limits of agreement were larger in inter-rater comparisons. In future studies care must be taken with variables collected on different days and with mandibular movements in the frontal and transversal planes.

Cognitive Correlates of Timed Up and Go Subtasks in Older People With Preserved Cognition, Mild Cognitive Impairment, and Alzheimer's Disease.

OBJECTIVE: To determine whether impaired Timed Up and Go Test (TUG) subtask performances are associated with specific cognitive domains among older people with preserved cognition (PC), mild cognitive impairment (MCI), and mild Alzheimer's disease (AD). DESIGN: TUG subtasks performances were assessed by the Qualisys motion system. Cognition was assessed by Addenbrooke's Cognitive Examination and the Frontal Assessment Battery (FAB). RESULTS: The highest correlations with transition subtasks were with aspects of executive function, i.e. the fluency domain in the PC group (n = 40), FAB scores in the MCI group (n = 40), and the visuospatial domain in the AD group (n = 38). No significant associations were found between the walking subtasks and cognition in any group. Multivariate linear regression models identified the fluency domain as an independent predictor of turn-to-walk and turn-to-sit measures in the PC group, and the visuospatial domain as an independent predictor of turn-to-walk and turn-to-sit measures in the AD group, adjusted for age and sex. CONCLUSIONS: Poorer executive functioning was associated with impaired transition mobility in all groups. The significant associations between visuospatial impairment and poor transition mobility in the AD participants may provide insight into why this group has an elevated fall risk.

The relationship between external knee moments and muscle co-activation in subjects with medial knee osteoarthritis.

PURPOSE: External knee moments are reliable to measure knee load but it does not take into account muscle activity. Considering that muscle co-activation increases compressive forces at the knee joint, identifying relationships between muscle co-activations and knee joint load would complement the investigation of the knee loading in subjects with knee osteoarthritis. The purpose of this study was to identify relationships between muscle co-activation and external knee moments during walking in subjects with medial knee osteoarthritis. METHODS: 19 controls (11 males, aged 56.6±5, and BMI 25.2±3.3) and 25 subjects with medial knee osteoarthritis (12 males, aged 57.3±5.3, and BMI 28.2±4) were included in this study. Knee adduction and flexion moments, and co-activation (ratios and sums of quadriceps, hamstring, and gastrocnemius) were assessed during walking and compared between groups. The relationship between knee moments and co-activation was investigated in both groups. FINDINGS: Subjects with knee osteoarthritis presented a moderate and strong correlation between co-activation (ratios and sums) and knee moments. INTERPRETATION: Muscle co-activation should be used to measure the contribution of quadriceps, hamstring, and gastrocnemius on knee loading. This information would cooperate to develop a more comprehensive approach of knee loading in this population.

Trunk biomechanics and its association with hip and knee kinematics in patients with and without patellofemoral pain.

Patellofemoral pain (PFP) is a common lower extremity condition observed in sports clinics. Recently, it has been suggested that trunk motion could affect hip and knee biomechanics in the frontal plane. Thus, the purpose of the study was compare trunk kinematics, strength and muscle activation between people with PFP and healthy participants. In addition, the associations among trunk biomechanics, hip and knee kinematics were analysed. Thirty people with PFP and thirty pain-free individuals participated. The peak ipsilateral trunk lean, hip adduction, and knee abduction were evaluated with an electromagnetic tracking system, and the surface electromyographic signals of the iliocostalis and external oblique muscle were recorded during single-leg squats. Trunk extension and trunk flexion with rotation isometric strength and side bridge tests were quantified using a handheld dynamometer. Compared with the control group, the PFP group demonstrated increased ipsilateral trunk lean, hip adduction and knee abduction (p = 0.02-0.04) during single-leg squat accompanied with decreased trunk isometric strength (p = < 0.001-0.009). There was no between-group difference in trunk muscle activation. Only in the control group, ipsilateral trunk lean was significantly correlated with hip adduction (r = -0.66) and knee abduction (r = 0.49); also, the side bridge test correlated with knee abduction (r = -0.51). Differences in trunk, hip and knee biomechanics were found in people with PFP. No relationship among trunk, hip and knee biomechanics was found in the PFP group, suggesting that people with PFP show different movement patterns compared to the control group.

Frontal plane biomechanics in males and females with and without patellofemoral pain.

PURPOSE: The study's purpose was to compare trunk, pelvis, hip, and knee frontal plane biomechanics in males and females with and without patellofemoral pain syndrome (PFPS) during stepping. METHODS: Eighty recreational athletes were equally divided into four groups: female PFPS, female controls, male PFPS, and male controls. Trunk, pelvis, hip, and knee frontal plane kinematics and activation of the gluteus medius were evaluated at 15°, 30°, 45°, and 60° of knee flexion during the downward and upward phases of the stepping task. Isometric hip abductor torque was also evaluated. RESULTS: Females showed increased hip adduction and knee abduction at all knee flexion angles, greater ipsilateral trunk lean and contralateral pelvic drop from 60° of knee flexion till the end of the stepping task (P = 0.027-0.001), diminished hip abductor torque (P < 0.001), and increased gluteus medius activation than males (P = 0.008-0.001). PFPS subjects presented increased knee abduction at all the angles evaluated; greater trunk, pelvis, and hip motion from 45° of knee flexion of the downward phase till the end of the maneuver; and diminished gluteus medius activation at 60° of knee flexion, compared with controls (P = 0.034-0.001). Females with PFPS showed lower hip abductor torque compared with the other groups. CONCLUSIONS: Females presented with altered frontal plane biomechanics that may predispose them to knee injury. PFPS subjects showed frontal plane biomechanics that could increase the lateral patellofemoral joint stress at all the angles evaluated and could increase even more from 45° of knee flexion in the downward phase until the end of the maneuver. Hip abductor strengthening and motor control training should be considered when treating females with PFPS.

Relationship among eccentric hip and knee torques, symptom severity and functional capacity in females with patellofemoral pain syndrome.

OBJECTIVE: To determine the relationships between eccentric hip and knee torques, symptom severity and functional capacity in females with patellofemoral pain syndrome (PFPS). DESIGN: Within-subject correlational study. SETTING: University biomechanics laboratory. PARTICIPANTS: 10 females diagnosed with PFPS. MAIN OUTCOME MEASURES: Eccentric strength of the hip abductors and lateral rotators, and knee extensors were assessed using an isokinetic dynamometer. A 10-cm visual analog scale was used to determine usual knee pain in the last week. The Anterior Knee Pain Scale (AKPS) was used to determine the functional capacity of the patients. RESULTS: The study found that the greater the eccentric knee extensor and hip lateral rotator torques, the higher the functional capacity of the patients (p = 0.02, r = 0.72; p = 0.02, r = 0.72). It was also shown that the greater hip lateral rotator torque, the less the usual pain reported in the last week (p = 0.004, r = -0.84). Despite the lack of statistical significance (p = 0.11), it was also found a modest negative relationship between the eccentric knee extensor torque and the usual pain reported in the last week (r = -0.56) that was considered clinically meaningful (d = 1.4). CONCLUSIONS: This study showed that eccentric knee extensor and hip lateral rotator torques were associated with functional capacity and pain level in females with PFPS. Further investigations should be carried out to verify the effects of an intervention program focused on the eccentric action of these muscles with respect to the symptoms in patients with PFPS.