Knee extensor and flexor muscle power explains stair ascension time in patients with unilateral late-stage knee osteoarthritis: a cross-sectional study

Differences in functional recovery after unilateral versus bilateral total knee arthroplasty

BACKGROUND

Understanding functional changes between unilateral and simultaneous bilateral total knee arthroplasty (TKA) patients remains limited. The purpose of this study was to investigate the differences in recovery times between unilateral and bilateral TKA.

METHODS

We retrospectively recruited patients who met the eligibility criteria. All patients engaged in a standard rehabilitation program and completed both self-reported questionnaires and performance-based physical function tests preoperatively, at 6 and 12 weeks postoperatively.

RESULTS

A total of 838 patients were included in this study. Those who underwent bilateral TKA (n = 281) were younger than those opting for unilateral TKA (n = 557), with no significant differences in baseline health status observed between the two groups. Both groups showed continuous improvements in pain, function, and performance-based physical functions from preoperatively to 12 weeks postoperatively. Notably, stiffness did not significantly improve from the preoperative to 6 weeks postoperatively and the stair-climbing test (SCT) showed delayed recovery, with deterioration at 6 weeks but subsequent improvement at 12 weeks in bilateral TKA group. Similarly, the recovery rate in the 6-min walking test (6MWT) was initially slow for the bilateral TKA group during the first 6 weeks, but later accelerated. Significant interactions between time and group were observed in the timed-up-and-go test, 6MWT, and SCT.

CONCLUSION

Patients who underwent bilateral TKA showed distinct recovery patterns, suggesting the need for tailored rehabilitation approaches compared those who underwent unilateral surgery. These findings underscore the need to provide patients with information about potential differences in recovery patterns based on their chosen surgical approach prior to surgery.

Association of Muscle Quantity and Quality With Knee Extension Strength in Knee Osteoarthritis: The Nagahama Study

OBJECTIVE

We aimed to examine whether lower-limb muscle quantity and quality assessed by bioelectric impedance analysis (BIA) were associated with knee extension strength and whether the association differed with knee osteoarthritis (OA) severity.

METHODS

We included 1,525 participants (63.6% women; mean ± SD age 68.0 ± 5.3 years) from the Nagahama Prospective Cohort. Knee extension strength was measured during maximum voluntary isometric contraction. Lower-limb muscle mass and the extracellular water (ECW)-to-intracellular water (ICW) ratio were used as indicators of muscle quantity and quality, respectively, and assessed via a BIA device. We executed multiple linear regression analyses to investigate the association of muscle quantity and quality with knee extension strength. Additionally, participants were classified into three groups with respect to OA severity and symptoms: control, early OA, and advanced OA groups; subgroup analyses were also executed.

RESULTS

The muscle mass (P < 0.001) and ECW-to-ICW ratio (P = 0.009) were significantly associated with knee extension strength. In the subgroup analysis, the muscle mass was significantly associated with knee extension strength (P < 0.001), but there was no association between ECW-to-ICW ratio and knee extension strength (P = 0.731) in the control group. In the early OA and advanced OA groups, the muscle mass (both P < 0.001) and ECW-to-ICW ratio (early OA, P = 0.034; advanced OA, P = 0.015) were significantly associated with knee extension strength.

CONCLUSION

Lower-limb muscle quality was associated with knee extension strength, and the association was stronger in patients with knee OA. These findings suggest that both muscle quantity and quality should be assessed to better understand muscle function in patients with knee OA.

The combination of osteoporosis and low lean mass correlates with physical function in end-stage knee osteoarthritis: A retrospective observational study

We aimed to investigate the prevalence of osteoporosis and low lean mass, either together or in isolation, and their association with physical function, pain, and quality of life (QOL) in patients with end-stage knee osteoarthritis (OA). This retrospective cross-sectional observational study included 578 patients (77 males and 501 females) diagnosed with end-stage knee OA. Patients were divided into 4 groups based on body composition parameters: control, osteoporosis, low lean mass, and osteoporosis + low lean mass. All participants underwent performance-based physical function tests, including a stair climbing test (SCT), a 6-minute walk test, a timed up and go test, and instrumental gait analysis, to examine spatiotemporal parameters. Self-reported physical function and pain levels were measured using the Western Ontario McMaster Universities Osteoarthritis Index and visual analog scale, respectively. Self-reported QOL was measured using the EuroQOL 5 dimensions (EQ-5D) questionnaire. Of 578 patients, 268 (46.4%) were included in the control group, 148 (25.6%) in the osteoporosis group, 106 (18.3%) in the low lean mass group, and 56 (9.7%) in the osteoporosis + low lean mass group. Analysis of variance revealed that the scores for the osteoporosis + low lean mass group in the SCT-ascent, SCT-descent, and timed up and go test were significantly higher, whereas those for the 6-minute walk test, gait speed, and cadence were significantly lower than those for the other groups (P < .05). After adjusting for age, sex, and body mass index, multiple linear regression analysis identified SCT-ascent (β = 0.140, P = .001, R2 = 0.126), SCT-descent (β = 0.182, P < .001, R2 = 0.124), gait speed (β = -0.116, P = .005, R2 = 0.079), and cadence (β = -0.093, P = .026, R2 = 0.031) as being significantly associated with osteoporosis + low lean mass. Thus, osteoporosis + low lean mass correlates with poor physical function, but not pain and QOL, in patients with end-stage knee OA.

The Value of a Standardized Knee Functional Assessment in Predicting the Outcomes of Total Knee Arthroplasty

Questionnaires and physical tests are tools to determine the ability of an individual to perform tasks of the daily living. In our institution, a standardized knee performance evaluation including patient-reported outcome measures (PROMs) and physical performance tests has been applied to all patients undergoing total knee arthroplasty (TKA). Our goal was to identify which preoperative tools influence the outcomes of a TKA and if physical performance tests can be of value if used along with PROMs in predicting functional outcomes. Classification and regression tree was used to analyze which preoperative factors influence function after TKA. Western Ontario and McMaster Universities Arthritis Index (WOMAC) function (WOMAC-F), 6-minute walk test (6MWT), and timed up and go (TUG) test at the 12th postoperative month were the dependent variables. Age, body mass index, preoperative WOMAC function and pain score, muscle strength, 6MWT, and TUG test score were used as preoperative predictors of dependent variables. TUG ≤19.3 seconds and age <62 years were preoperative predictors of better scores in the WOMAC-F (5.5). Strength of extensor muscles of the nonoperated knee ≥99.43 N·m/kg and 6MWT> 328 m were preoperative predictors of a better postoperative 6MWT (499 m). TUG <12.3 seconds and 6MWT ≥421 m were preoperative predictors of better postoperative TUG (7.3 seconds). Preoperative performance in physical tests had an influence on postoperative outcome scores than PROMs after TKA. Less age, good muscular strength, greater capacity of walking, and smaller TUG times were associated with better outcomes.

Reliability, validity and responsiveness of the Step Up and Down (StUD) test for individuals with symptomatic knee osteoarthritis

BACKGROUND

Stair climbing test (SCT) has been suggested as the first task affected in individuals with symptomatic knee osteoarthritis (KOA). However, there are environmental barriers for the execution of the 9- to 12-step SCT. Thus, we developed a feasible one-step SCT that could be completed in 15s.

OBJECTIVE

To check the clinimetric properties of the 15s Step Up and Down (StUD) test in individuals with KOA.

DESIGN

Prospective validity study.

METHOD

Eighty-two individuals with KOA participated in this study. The test-retest reliability of the StUD test was measured with a 1-week interval. The construct validity and responsiveness were assessed by testing predefined hypotheses. For this, the 30s Chair Stand Test (30CS), Timed Up and Go Test (TUG), quadriceps strength, Knee Injury and Osteoarthritis Outcome Score (KOOS), and Lequesne Algofunctional Index were used as comparator instruments.

RESULTS

The StUD test presented good test-retest reliability (ICC = 0.87; 95% CI = 0.79-0.91) and showed a moderate to good correlation with the 30CS (r = 0.65), TUG (r = -0.56), and quadriceps strength (r = 0.41). We found a higher correlation between the StUD test and the performance-based tests than the patient-reported outcome measures. The StUD test was responsive, with five out of the six (83.3%) hypotheses confirmed.

CONCLUSION

StUD test showed good reliability, adequate validity and responsiveness. Our findings suggest that StUD is a useful performance-based test for individuals with KOA.

Should We Use Unilateral or Bilateral Tasks to Assess Maximal and Explosive Knee Extensor Strength in Patients with Knee Osteoarthritis? A Cross-Sectional Study

Deficits in maximal and explosive knee extensor strength, which are usually assessed with unilateral tasks, are substantial in patients with knee osteoarthritis (KOA). The aim of this study was to investigate the clinical relevance of unilateral vs. bilateral tasks for assessing knee extensor strength in patients with KOA. This was achieved primarily by comparing unilateral and bilateral inter-limb strength asymmetries and secondarily by examining the relationship between unilaterally and bilaterally measured strength, and performance-based and self-reported function. Twenty-four patients with unilateral KOA (mean age: 65 ± 7 years) performed isometric gradual and explosive maximal voluntary contractions to assess, respectively their maximal and explosive strength. Performance-based and self-reported function were also evaluated with standard functional tests and questionnaires, respectively. Inter-limb asymmetries of maximal and explosive strength did not differ significantly between unilateral (mean asymmetry: 26 ± 15%) and bilateral tasks (22 ± 21%). In the same way, the relationships between knee extensor strength-measured either unilaterally or bilaterally-and performance-based or self-reported function were not influenced by the type of task. In conclusion, it does not seem to make a difference in terms of clinical relevance whether maximal and explosive knee extensor strength are evaluated with unilateral or bilateral tasks in KOA patients.

COMPARATIVE ANALYSIS OF KNEE MUSCLE DAMAGE OF DIFFERENT ATHLETES

ABSTRACT Introduction: The knee joint is the most complex weight-bearing joint in the human body. An athlete's knee joint is prone to injury in competitive sports; it is one of the most common injuries and, in some sports, severe meniscus and cruciate ligament injuries occur frequently as, for example, in handball and soccer, and can even end the career of an elite athlete. Objective: To explore the comparison of knee flexion and extension force injury in different athletes. Methods: The characteristics of the flexor and extensor muscle of the knee joint in handball, football and cycling were studied with the isokinetic technique. Results: The role of the knee joint in different types of sports played by athletes is obviously different, which leads to the different requirements of the flexor and extensor muscle in the knee joint. Conclusions: The key to improving the conditions of superior strength and preventing sports injury is to develop the features of specific strength reasonably. Level of evidence II; Therapeutic studies - investigation of treatment results.

Impaired muscle capacity of the hip and knee in individuals with isolated patellofemoral osteoarthritis: a cross-sectional study

AIMS

The aims of this study were to compare the capacity of the knee and hip muscles between individuals with and without isolated patellofemoral osteoarthritis (PFOA) and to evaluate the impact of PFOA on pain, stiffness, and physical function.

METHODS

This cross-sectional study evaluated muscle capacity of the hip and knee using an isokinetic dynamometer. The isokinetic variables used in the statistical analysis were peak torque, total work, and average power. Pain, stiffness, and physical function were assessed using questionnaires.

RESULTS

A total of 26 individuals participated in the study (13 with PFOA and 13 controls). The PFOA group exhibited lower peak torque, total work, and average power for knee extension and flexion in the concentric mode (p ⩽ 0.01) as well as lower peak torque and total work for knee extension (p ⩽ 0.005) and lower total work for knee flexion (p = 0.05) in the eccentric mode. The PFOA group exhibited lower peak torque of the extensor, abductor, adductor, and internal rotator muscles of the hip (p ⩽ 0.05), less total work of the abductor and adductor muscles (p ⩽ 0.04), and lower average power of eccentric adduction of the hip (p = 0.01) compared with the healthy controls. Compared with the control group, the PFOA group had a higher level of pain, stiffness, and compromised physical functioning self-reported (p ⩽ 0.005).

CONCLUSION

Participants with PFOA exhibited impairments regarding muscle capacity of the hip and knee, higher level of pain and stiffness as well as compromised physical functioning in comparison with healthy controls.

Muscle strength gains after strengthening exercise explained by reductions in serum inflammation in women with knee osteoarthritis

Background Individuals with knee osteoarthritis have elevated circulating inflammatory markers and altered cartilage properties but it is unclear if these features adapt to exercise. We aimed to determine (1) whether inflammatory markers, cartilage transverse relaxation time and thickness mediate the effect of body mass index (BMI) on quadriceps strength at baseline; and (2) whether these changes explain variance in quadriceps strength improvements after 12 weeks of exercise in women with knee osteoarthritis. Methods This secondary analysis (17 women with clinical knee osteoarthritis) of a randomized control trial compared supervised group interventions, 3 times/week for 12 weeks (36 sessions): (a) weight-bearing progressive resistive quadriceps exercise or (b) attention control. (1) From baseline, separate linear regressions were conducted with strength (Nm/kg) as the dependent, BMI as the predictor, and c-reactive protein, tumor necrosis factor, interleukin-6, cartilage transverse relaxation time or thickness as potential mediators. (2) Multiple linear regression analyses were completed with 12-week strength change (post-pre) as the dependent, change in serum inflammatory markers and cartilage measurements as predictors, and age, BMI and adherence as covariates. Findings (1) At baseline, there was no mediation. (2) A decrease in each of interleukin-6 (β = -0.104 (95% confidence intervals: -0.172, -0.036), R² = 0.51, P < 0.007) and tumor necrosis factor (β = -0.024 (-0.038, -0.009), R² = 0.54, P < 0.005) was associated with strength gains. Interpretation At baseline, inflammatory markers and cartilage measurements do not act as mediators of BMI on quadriceps strength. After 12 weeks of exercise, reduced interleukin-6 and tumor necrosis factor were associated with increased quadriceps strength in women with knee osteoarthritis.

Performance-based physical function correlates with walking speed and distance at 3 months post unilateral total knee arthroplasty

BACKGROUND

After total knee arthroplasty (TKA), walking speed and distance are main concerns of patients.

RESEARCH QUESTION

Which physical functions affect walking speed and distance after TKA?

METHODS

Cross-sectional data from 149 patients who underwent unilateral primary TKA and completed performance-based physical function tests. Instrumental gait evaluation for spatiotemporal parameters, isometric knee extensor and flexor strength of both knees, 6-minute walk test (6MWT), timed up-and-go (TUG) test, timed stair climbing test (SCT), and knee flexion and extension range of motion (ROM) of surgical knee were examined. Western Ontario McMaster Universities Osteoarthritis Index (WOMAC) and EuroQol five dimensions (EQ-5D) questionnaires were also performed.

RESULTS

Univariate analyses revealed that post-operative walking speed showed significant positive correlations with cadence, stride length, propulsion index of surgical and non-surgical knee, peak torque (PT) of the extensor of surgical and non-surgical knee and flexor of surgical and non-surgical knee, 6MWT, EQ-5D, and significant negative correlations with gait cycle duration, TUG, SCT-ascent and descent, and WOMAC-pain scores. Post-operative walking distance had significant positive correlations with walking speed, cadence, stride length, swing phase duration, propulsion index of surgical and non-surgical knee, PT of the extensor of surgical and non-surgical knee, EQ-5D, and significant negative correlation with gait cycle duration, double support duration, TUG, SCT-ascent and descent. In the multivariate linear regression analyses, TUG, cadence, stride length and propulsion index of non-surgical knee were factor correlated with post-operative walking speed. The SCT-ascent and descent, TUG and propulsion index of surgical knee were factor correlated with post-operative walking distance.

SIGNIFICANCE

Physical performance factors correlated with walking speed and distance at 3 months after surgery. Based on these observations, rehabilitation of bilateral muscle strength and functional mobility would be important for functional recovery after unilateral TKA.

Knee Extensor Muscle Strength Is More Important Than Postural Balance for Stair-Climbing Ability in Elderly Patients with Severe Knee Osteoarthritis

Knee osteoarthritis is a chronic joint disease which damages articular cartilage. In its severe stages, it results in impairments in balance and muscle strength loss, which affect daily life activities such as walking or climbing stairs. This study sought to investigate associated factors with stair-climbing ability in this population, with special interest in measuring the relevance of postural balance for this task. Forty-four patients scheduled to undergo unilateral total knee arthroplasty were assessed. Timed up and go test, stair ascent-descent test, three different isometric strength tests (knee flexion, knee extension and hip abduction), active knee extension and flexion range of movement and static postural balance assessment were evaluated. Spearman's correlation coefficients and multiple linear regression analysis determined the strength of association between the different variables and stair-climbing time. No significant association between the stair-climbing time and static balance was found. Significant associations were found between stair-climbing time and timed up and go (r = 0.71; p < 0.0001) and maximal knee extensor strength (r = -0.52; p = 0.0003). One-year increase in age was associated with 0.15 s (95% CI 0.00 to 0.30) slower stair-climbing time. In conclusion, muscle strength is more important than postural balance for stair-climbing ability in this population.

Estimación de par basada en electromiografía de superficie: potencial herramienta para la rehabilitación de rodilla

Introducción. Múltiples estudios de procesamiento de señales han reportado la aplicación de las señales de electromiografía de superficie (sEMG) en robótica y en procesos de rehabilitación motora.Objetivo. Realizar una revisión de la literatura sobre el uso de señales de sEMG como alternativa para la estimación del par de rodilla con el fin de medir objetivamente el progreso de los pacientes en las diferentes etapas de rehabilitación de lesiones de rodilla.Materiales y métodos. Se realizó una revisión de la literatura publicada entre 1986 y 2018, sin límites geográficos, en las bases de datos Engineering Village, IEEE Xplore, ScienceDirect, Web of Science, Scopus y PubMed mediante la combinación de 8 términos de búsqueda.Resultados. Al finalizar la búsqueda inicial se obtuvieron 355 registros. Luego de realizar la remoción de duplicados esta cifra descendió a 308, los cuales fueron analizados para determinar si cumplían con los criterios de inclusión. Finalmente se incluyeron 18 estudios que describen de forma comparativa cómo estimar el par a partir de señales de sEMG.Conclusiones. El uso de señales de sEMG para calcular el par en una articulación es una herramienta alternativa que permite al terapeuta acceder a parámetros cuantitativos y, de esta forma, valorar el progreso de los pacientes durante el proceso de rehabilitación de rodilla.

Transcutaneous Electrical Nerve Stimulation Improves Stair Climbing Capacity in People with Knee Osteoarthritis

This study aimed to examine the effect of transcutaneous electrical nerve stimulation (TENS) on stair climbing capacity in individuals with pre-radiographic to mild knee osteoarthritis (OA). This is a secondary analysis of data from a single, participant-blinded, randomized controlled trial with a pre-post design. Participants with pre-radiographic to mild knee OA (mean age, 59.1 years; 72.9% women) were randomly assigned into two groups, a TENS (n = 30) and a sham-TENS groups (n = 29). TENS or sham-TENS treatments were applied to all participants by using the prototype TENS device with pre-specified parameters. The primary outcome measures included valid and reliable functional measures for stair climbing (stair-climb test [SCT]), visual analog scale for knee pain during the SCT, and quadriceps muscle strength. TENS improved SCT time by 0.41 s (95% confidence interval [CI]: 0.07, 0.75). The time reduction in the transition phase explains the TENS therapeutic effect. Post-hoc correlation analyses revealed a non-significant but positive relationship between the pain relief effect and improved 11-step SCT time in the TENS group but not in the sham-TENS group. These results indicate that the TENS intervention may be an option for reducing the burden of early-stage knee OA.

Functional Outcomes After Critical Pathway for Inpatient Rehabilitation of Total Knee Arthroplasty

OBJECTIVE

To investigate functional outcomes after the application of a critical pathway for inpatient rehabilitation of total knee arthroplasty (TKA).

METHODS

A total of 184 patients (57 males and 127 females; average age, 71.5±5.9 years) who underwent unilateral or bilateral TKA were included. The critical pathway included early, intensive individualized rehabilitation exercises. Patients completed the following performance-based physical function tests: the stair climbing test (SCT), 6-minute walk test (6MWT), and Timed Up and Go test (TUG) as well as measurement of isometric knee flexor and extensor strength of the operated knee, gait speed, and range of knee flexion and extension. Self-reported physical function and pain were measured using the Western Ontario McMaster Universities Osteoarthritis Index (WOMAC) and visual analog scale (VAS), respectively, and self-reported quality of life was measured using the EuroQoL 5 dimension (EQ-5D) questionnaire. These evaluations were performed preoperatively and at 1 month and 3 months postoperatively.

RESULTS

Performance-based and self-reported physical function and quality of life measures improved nonlinearly over time. Specifically, the 6WMT, TUG, gait speed, WOMAC-pain, WOMAC-function, VAS, and EQ-5D scores showed a significant improvement at 1-month post-TKA, whereas SCT, peak torque of the knee extensors and flexors, and WOMAC-stiffness scores showed gradual, but substantial, improvements over 3 months. There were between-group differences (unilateral and bilateral TKA groups) in the time course of the SCT, 6MWT, TUG, VAS, WOAMC-stiffness, and WOMAC-function results.

CONCLUSION

Patients who underwent critical pathway rehabilitation after TKA showed significant improvements in functional measurements during the first 3 months post-surgery.

Relationship Between Strength Parameters and Functional Performance Tests in Patients With Severe Knee Osteoarthritis

BACKGROUND

Decreased leg muscle strength is a major determinant of reduced function in patients with knee osteoarthritis (OA). The identification of a strength parameter that is best correlated with functional performance is important for monitoring rehabilitation results.

OBJECTIVE

To determine which muscle strength measurements show the highest correlation with functional capacity in patients with severe knee OA shortly before total knee arthroplasty (TKA).

DESIGN

Cross-sectional exploratory study.

SETTING

Outpatient rehabilitation department at a university teaching hospital.

PATIENTS

The sample included 75 patients (51 female) scheduled for primary TKA, recruited through multistage sampling.

METHODS OR INTERVENTIONS

Independent variables were peak isometric, isokinetic concentric, and eccentric leg extensor strength measured on the leg press, as well as peak isometric knee extensor strength measured on the strength chair. Two multiple regression analyses were performed, one including all strength measures and the other including all of the strength ratios. Pearson correlation coefficients were calculated between the strength measures and functional test scores.

MAIN OUTCOME MEASUREMENTS

Dependent variables were the Timed Up and Go Test (TUG) and the Stair Test (ST).

RESULTS

The regression analysis including all strength measures could explain 11.9% of the variance of the TUG (P = .068, not significant [NS]) and 21.5% of the variance of the ST (P = .009, significant). The regression model for the strength ratios explained 11.8% of the variance of the TUG (P = .090, NS) and 6.3% of the ST (P = .217, NS).

CONCLUSIONS

Although univariate analysis confirmed significant correlations between strength measurements and functional tests, multiple regression analysis revealed a higher predictive value for the ST than for the TUG. The use of both muscle strength tests and performance-based function tests is advisable to evaluate functional impairments of patients with knee OA.

LEVEL OF EVIDENCE

III.

Self-efficacy, pain, and quadriceps capacity at baseline predict changes in mobility performance over 2 years in women with knee osteoarthritis

This study examined the extent to which baseline measures of quadriceps strength, quadriceps power, knee pain and self-efficacy for functional tasks, and their interactions, predicted 2-year changes in mobility performance (walking, stair ascent, stair descent) in women with knee osteoarthritis. We hypothesized that lesser strength, power and self-efficacy, and higher pain at baseline would each be independently associated with reduced mobility over 2 years, and each of pain and self-efficacy would interact with strength and power in predicting 2-year change in stair-climbing performance. This was a longitudinal, observational study of women with clinical knee osteoarthritis. At baseline and follow-up, mobility was assessed with the Six-Minute Walk Test, and stair ascent and descent tasks. Quadriceps strength and power, knee pain, and self-efficacy for functional tasks were also collected at baseline. Multiple linear regression examined the extent to which 2-year changes in mobility performances were predicted by baseline strength, power, pain, and self-efficacy, after adjusting for covariates. Data were analyzed for 37 women with knee osteoarthritis over 2 years. Lower baseline self-efficacy predicted decreased walking (β = 1.783; p = 0.030) and stair ascent (β = -0.054; p < 0.001) performances over 2 years. Higher baseline pain intensity/frequency predicted decreased walking performance (β = 1.526; p = 0.002). Lower quadriceps strength (β = 0.051; p = 0.015) and power (β = 0.022; p = 0.022) interacted with lesser self-efficacy to predict worsening stair ascent performance. Strategies to sustain or improve mobility in women with knee osteoarthritis must focus on controlling pain and boosting self-efficacy. In those with worse self-efficacy, developing knee muscle capacity is an important target.

Effects of Motor Learning on Clinical Isokinetic Test Performance in Knee Osteoarthritis Patients

OBJECTIVES:

To analyze the effects of motor learning on knee extension-flexion isokinetic performance in knee osteoarthritis patients.

METHODS:

One hundred and thirty-six middle-aged and older sedentary individuals (111 women, 64.3±9.9 years) with knee osteoarthritis (130 patients with bilateral) and who had never performed isokinetic testing underwent two bilateral knee extension-flexion (concentric-concentric) isokinetic evaluations (5 repetitions) at 60°/sec. The tests were first performed on the dominant leg with 2 min of recovery between test, and following a standardized warm-up that included 3 submaximal isokinetic repetitions. The same procedure was repeated on the non-dominant leg. The peak torque, peak torque adjusted for the body weight, total work, coefficient of variation and agonist/antagonist ratio were compared between tests.

RESULTS:

Patients showed significant improvements in test 2 compared to test 1, including higher levels of peak torque, peak torque adjusted for body weight and total work, as well as lower coefficients of variation. The agonist/antagonist relationship did not significantly change between tests. No significant differences were found between the right and left legs for all variables.

CONCLUSION:

The results suggest that performing two tests with a short recovery (2 min) between them could be used to reduce motor learning effects on clinical isokinetic testing of the knee joint in knee osteoarthritis patients.

The contribution of leg press and knee extension strength and power to physical function in people with knee osteoarthritis: A cross-sectional study

The purposes of this study were to 1) determine the additional contributions of leg press and knee extensor power, over and above that of strength, to the performance of physical function tasks in people with knee osteoarthritis, and 2) compare the ability of bilateral leg press to unilateral knee extensor strength and power to predict functional task performance.

METHODS

A cross-sectional, exploratory study of 40 individuals with tibiofemoral knee osteoarthritis resulting in moderate impairments in physical function was conducted. Physical function (Get-up and Go, timed stair climb and descent, and five time chair rise) and muscle performance (leg press and knee extension strength and power) were assessed.

RESULTS

After controlling for covariates and strength, leg press, but not knee extensor, power explained additional variance in physical function (11% and 21%). Conversely, adding strength to regression models including covariates and power did not consistently improve the prediction of physical function. Additionally, leg press power consistently explained more variance in physical function (44 to 57%) than involved (24 to 34%) or uninvolved (28 to 48%) knee extension power.

CONCLUSIONS

Leg press power may be a more functionally relevant measure of muscle performance than knee extension strength in this population. Future studies should investigate the effectiveness of interventions specifically designed to improve leg press power in people with knee osteoarthritis.