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Validity and Responsiveness of Floor Sitting-Rising Test in Post–Total Knee Arthroplasty: A Cohort Study

Open AccessPublished:April 18, 2020DOI:https://doi.org/10.1016/j.apmr.2020.03.012

      Abstract

      Objectives

      To assess the construct validity and responsiveness of the floor sitting-rising test (SRT) in individuals with total knee arthroplasty (TKA).

      Design

      Cohort study with 6-month follow-up. Secondary analysis using data from a randomized controlled trial.

      Setting

      An outpatient rehabilitation research center.

      Participants

      Participants (N=240) enrolled in the parent study who had unilateral primary TKA.

      Intervention

      Participants in the parent study underwent 12 weeks of exercise programs.

      Main Outcome Measures

      Validity analysis correlated baseline data of participants who completed the SRT and measures of knee motion, muscle strength, performance-based tests, and patient-reported outcomes of physical and psychosocial function. Responsiveness analysis used the 3- and 6-month follow-up data. Effect sizes were calculated using changes from baseline. Areas under the receiving operating characteristics curve were calculated using a global rating of change as the external anchor.

      Results

      Of the 240 participants (148 women; age, 70±7y), 180 (75%) were able to perform the SRT at baseline. Performers scored significantly better in all physical function tests (P<.0001) than nonperformers. SRT scores generally converged with measures of knee impairment and performance-based tests (associations ranged from small [r=0.15; P=.0516] to moderate [r=0.52; P<.0001]). SRT scores associated with self-efficacy for function (r=0.34; P<.0001) and fear of falls (r=-0.25; P=.001). At 3 (n=174) and 6 months (n=160), SRT effect sizes were 0.38 (95% confidence interval, 0.25-0.52) and 0.42 (95% confidence interval, 0.25-0.60), and areas under the curve were 0.59 (95% confidence interval, 0.49-0.69) and 0.62 (95% confidence interval, 0.52-0.73), respectively.

      Conclusions

      The results add evidence to the validity of the SRT in patients after TKA. The strength of the associations suggests that the SRT measures a physical function construct not captured by the other tests. The magnitude of indices of responsiveness for the SRT were similar to other performance-based tests, indicating comparable responsiveness to more widespread tests of functional performance.

      Keywords

      List of abbreviations:

      ASES (Arthritis Self-Efficacy Scale), AUC (area under the curve), COPM (Canadian Occupational Performance Measure), GRC (Global Rating of Change), PRO (patient-reported outcome), ROC (receiver operating characteristic), ROM (range of motion), SRT (sitting-rising test), TKA (total knee arthroplasty), WOMAC-PF (Western Ontario and McMaster Universities Osteoarthritis Index Physical Function subscale)
      Most individuals who undergo a total knee arthroplasty (TKA) experience good outcomes, including decreased knee pain and improved quality of life.
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      What functional activities are important to patients with knee replacements?.
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      Cost-effectiveness of total knee arthroplasty in the United States: patient risk and hospital volume.
      However, many continue to have limited ability to squat, kneel,
      • Noble P.C.
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      Does total knee replacement restore normal knee function?.
      and sit down and rise from the floor.
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      Importance of squatting and sitting on the floor: perspectives and priorities of rural Indian patients with stroke.
      Floor sit-to-rise is necessary for routine tasks such as getting in and out of a bathtub and cleaning one’s house.
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      Importance of squatting and sitting on the floor: perspectives and priorities of rural Indian patients with stroke.
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      • Suda Y.
      Factors affecting the achievement of Japanese-style deep knee flexion after total knee arthroplasty using posterior-stabilized prosthesis with high-flex knee design.
      It is also important for cultural integration. Many South Asian and African countries endorse floor sit-to-rise as an important performance-based task for eating, socializing, meditation,
      • Acker S.M.
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      Knee kinematics of high-flexion activities of daily living performed by male Muslims in the Middle East.
      and prayer.
      • Prakash V.
      • S R.P.
      • Hariohm K.
      • V S.S.
      • Alagumoorthi G.
      Importance of squatting and sitting on the floor: perspectives and priorities of rural Indian patients with stroke.
      ,
      • Niki Y.
      • Takeda Y.
      • Harato K.
      • Suda Y.
      Factors affecting the achievement of Japanese-style deep knee flexion after total knee arthroplasty using posterior-stabilized prosthesis with high-flex knee design.
      ,
      • de Araújo C.G.
      [Sit-up test: presentation of an evaluation procedure in exercise and sports medicine] [Portuguese].
      The sitting-rising test (SRT) was introduced to objectively assess the ability of individuals to sit and rise from the floor.
      • de Araújo C.G.
      [Sit-up test: presentation of an evaluation procedure in exercise and sports medicine] [Portuguese].
      ,
      • Brito L.B.
      • Ricardo D.R.
      • Araujo D.S.
      • Ramos P.S.
      • Myers J.
      • Araujo C.G.
      Ability to sit and rise from the floor as a predictor of all-cause mortality.
      It provides information about essential components of physical function, including lower extremity muscle strength,
      • Brito L.B.
      • Ricardo D.R.
      • Araujo D.S.
      • Ramos P.S.
      • Myers J.
      • Araujo C.G.
      Ability to sit and rise from the floor as a predictor of all-cause mortality.
      joint mobility,
      • Acker S.M.
      • Cockburn R.A.
      • Krevolin J.
      • Li R.M.
      • Tarabichi S.
      • Wyss U.P.
      Knee kinematics of high-flexion activities of daily living performed by male Muslims in the Middle East.
      ,
      • Brito L.B.
      • de Araujo D.S.
      • de Araujo C.G.
      Does flexibility influence the ability to sit and rise from the floor?.
      ,
      • Ohno H.
      • Murata M.
      • Ozu S.
      • Matsuoka N.
      • Kawamura H.
      • Iida H.
      Midterm outcomes of high-flexion total knee arthroplasty on Japanese lifestyle.
      and balance. During SRT, an examiner quantifies the number of supports the subject uses to sit down and rise from the floor and the number of times the subject is unsteady while performing these activities.
      • de Araújo C.G.
      [Sit-up test: presentation of an evaluation procedure in exercise and sports medicine] [Portuguese].
      To our knowledge, the responsiveness of the SRT has not been tested and its validity and reliability have been assessed in only a few studies.
      • Brito L.B.
      • Ricardo D.R.
      • Araujo D.S.
      • Ramos P.S.
      • Myers J.
      • Araujo C.G.
      Ability to sit and rise from the floor as a predictor of all-cause mortality.
      ,
      • Ng S.S.
      • Fong S.S.
      • Chan W.L.
      • et al.
      The sitting and rising test for assessing people with chronic stroke.
      Brito et al
      • Brito L.B.
      • Ricardo D.R.
      • Araujo D.S.
      • Ramos P.S.
      • Myers J.
      • Araujo C.G.
      Ability to sit and rise from the floor as a predictor of all-cause mortality.
      demonstrated that the SRT scores predicted all-cause mortality in a cohort of 2002 healthy older adults over the following 6 years, with lower-scoring subjects exhibiting 5 to 6 times higher risk of mortality compared with those in the reference group. Ng et al
      • Piva S.R.
      • Moore C.G.
      • Schneider M.
      • Gil A.B.
      • Almeida G.J.
      • Irrgang J.J.
      A randomized trial to compare exercise treatment methods for patients after total knee replacement: protocol paper.
      demonstrated that the SRT correlated with ankle strength and reported good inter-rater (intraclass correlation coefficient, .95) and test-retest (intraclass correlation coefficient, .85) reliability in patients after stroke.
      In a recent randomized study of exercise after TKA,
      • Piva S.R.
      • Moore C.G.
      • Schneider M.
      • Gil A.B.
      • Almeida G.J.
      • Irrgang J.J.
      A randomized trial to compare exercise treatment methods for patients after total knee replacement: protocol paper.
      patient stakeholders suggested testing the ability to sit and rise from the floor as a performance-based measure, which supports the face value of this test. Evidence of the SRT’s validity and responsiveness in TKA is needed to establish the test’s clinical usefulness. This study examined the validity and responsiveness of the SRT in patients after TKA. We hypothesized that SRT scores would converge and be moderately associated with other physical function measures and diverge from psychosocial measures. We also hypothesized that the indices of SRT responsiveness would be modest and similar in magnitude to the other measures of physical function commonly used in exercise trials after TKA.

      Methods

      This secondary analysis used data obtained from a randomized clinical trial on exercise after TKA conducted from January 2015 to November 2017 in the Department of Physical Therapy, University of Pittsburgh.
      • Piva S.R.
      • Moore C.G.
      • Schneider M.
      • Gil A.B.
      • Almeida G.J.
      • Irrgang J.J.
      A randomized trial to compare exercise treatment methods for patients after total knee replacement: protocol paper.
      Participants signed an informed consent approved by the University of Pittsburgh Institutional Review Board (PRO14080261). All clinical measures were assessed at baseline, and 3 and 6 months after exercise intervention. The interventions used in the parent study included rehabilitative exercises in an outpatient setting, group exercise classes in a community center, and usual medical care.
      • Piva S.R.
      • Moore C.G.
      • Schneider M.
      • Gil A.B.
      • Almeida G.J.
      • Irrgang J.J.
      A randomized trial to compare exercise treatment methods for patients after total knee replacement: protocol paper.

      Participants

      Inclusion criteria were age of 60 years or older, unilateral primary TKA 2 to 4 months before screening, moderate functional limitation (score ≥9 on the Western Ontario and McMaster Universities Osteoarthritis Index Physical Function subscale [WOMAC-PF]), ability to read and write English, willingness to be randomized, and medical clearance to exercise.
      • Piva S.R.
      • Moore C.G.
      • Schneider M.
      • Gil A.B.
      • Almeida G.J.
      • Irrgang J.J.
      A randomized trial to compare exercise treatment methods for patients after total knee replacement: protocol paper.
      Exclusion criteria were contraindications to exercise,
      • Nelson M.E.
      • Rejeski W.J.
      • Blair S.N.
      • et al.
      Physical activity and public health in older adults: recommendation from the American College of Sports Medicine and the American Heart Association.
      ,
      • Williams M.A.
      • Haskell W.L.
      • Ades P.A.
      • et al.
      Resistance exercise in individuals with and without cardiovascular disease: 2007 update: a scientific statement from the American Heart Association Council on Clinical Cardiology and Council on Nutrition, Physical Activity, and Metabolism.
      neuromuscular disorders of the lower extremities, inability to independently walk 50 meters, current participation in supervised exercise, terminal illness, plans to have another TKA, or unavailability during the study period.

      Clinical measures

      Performance-based physical function and physical impairments

      The SRT assesses the ability to sit and rise from the floor without assistance. The SRT is administered on a flat, nonslippery surface. Subjects wear nonrestricting clothing. All participants are given the same instruction: “Without worrying about the speed of movement, try to sit and then rise from the floor, using the minimum support that you believe is needed.”
      • Brito L.B.
      • Ricardo D.R.
      • Araujo D.S.
      • Ramos P.S.
      • Myers J.
      • Araujo C.G.
      Ability to sit and rise from the floor as a predictor of all-cause mortality.
      Participants perform a practice trial and the examiner gives feedback to improve participants’ test performance.
      • Brito L.B.
      • Ricardo D.R.
      • Araujo D.S.
      • Ramos P.S.
      • Myers J.
      • Araujo C.G.
      Ability to sit and rise from the floor as a predictor of all-cause mortality.
      Then, participants performed the test. Identical scoring methods are used for both the sitting and rising phases. Each phase (partial score) starts with 5 points. One point is subtracted each time the participant uses hands (placing hands on the floor while sitting or pushing with hands on knees during rising) or legs (using the lateral leg to push up or kneeling on one or both knees to stand) to execute the task. One-half point is subtracted for visible loss of balance during the maneuver. The final score is the sum of the sitting and rising partial scores, with a maximal score of 10.
      • Brito L.B.
      • Ricardo D.R.
      • Araujo D.S.
      • Ramos P.S.
      • Myers J.
      • Araujo C.G.
      Ability to sit and rise from the floor as a predictor of all-cause mortality.
      The single-leg balance test records the amount of time a participant balances on 1 leg while keeping both hands on the hips, for a maximum of 60 seconds. The test is stopped if the swing leg touches the floor, the support foot moves on the floor, or the arms swing away from the hips.
      • Curb J.D.
      • Ceria-Ulep C.D.
      • Rodriguez B.L.
      • et al.
      Performance-based measures of physical function for high-function populations.
      This test is performed bilaterally and repeated 3 times on each leg. The score is the averaged time of each leg.
      The timed Up and Go test records the amount of the time it takes for a participant to rise from a chair, walk for 3 meters, turn, and sit down on the same chair.
      • Bennell K.
      • Dobson F.
      • Hinman R.
      Measures of physical performance assessments: Self-Paced Walk Test (SPWT), Stair Climb Test (SCT), Six-Minute Walk Test (6MWT), Chair Stand Test (CST), Timed Up & Go (TUG), Sock Test, Lift and Carry Test (LCT), and Car Task.
      The 30-second Sit-to-Stand test counts the number of sit-to-stands a participant can complete in 30 seconds, using a chair that is 18 inches high and without armrests.
      • Curb J.D.
      • Ceria-Ulep C.D.
      • Rodriguez B.L.
      • et al.
      Performance-based measures of physical function for high-function populations.
      The stair climb test records the number of times a participant climbs up and down a set of 11 stairs (30 cm depth, 17 cm height), using a handrail on the preferred side.
      • Almeida G.J.
      • Schroeder C.A.
      • Gil A.B.
      • Fitzgerald G.K.
      • Piva S.R.
      Interrater reliability and validity of the stair ascend/descend test in subjects with total knee arthroplasty.
      The 4-meter walk test
      • Hardy S.E.
      • Perera S.
      • Roumani Y.F.
      • Chandler J.M.
      • Studenski S.A.
      Improvement in usual gait speed predicts better survival in older adults.
      and the 40-meter fast-paced walk test
      • Wright A.A.
      • Cook C.E.
      • Baxter G.D.
      • Dockerty J.D.
      • Abbott J.H.
      A comparison of 3 methodological approaches to defining major clinically important improvement of 4 performance measures in patients with hip osteoarthritis.
      assess gait speed by recording the amount of time needed to walk 4 meters at a self-selected pace and 40 meters at a fast pace. The 6-minute walk test measures the distance walked during 6 minutes on an unobstructed circuit.
      • Curb J.D.
      • Ceria-Ulep C.D.
      • Rodriguez B.L.
      • et al.
      Performance-based measures of physical function for high-function populations.
      Passive range of motion (ROM) of knee extension and flexion is measured with a standard goniometer.
      • Gogia P.P.
      • Braatz J.H.
      • Rose S.J.
      • Norton B.J.
      Reliability and validity of goniometric measurements at the knee.
      The isometric strength of knee extensors and hip abductors is assessed with isokinetic and hand-held dynamometers, respectively. Detailed methods of these strength tests have been described elsewhere.
      • Piva S.R.
      • Teixeira P.E.
      • Almeida G.J.
      • et al.
      Contribution of hip abductor strength to physical function in patients with total knee arthroplasty.
      Several studies have supported the good psychometric properties of reliability and validity of the performance-based tests used in this study and described above. These studies have used populations of healthy older adults, older adults with arthritic conditions, and adults after TKA.
      • Curb J.D.
      • Ceria-Ulep C.D.
      • Rodriguez B.L.
      • et al.
      Performance-based measures of physical function for high-function populations.
      • Bennell K.
      • Dobson F.
      • Hinman R.
      Measures of physical performance assessments: Self-Paced Walk Test (SPWT), Stair Climb Test (SCT), Six-Minute Walk Test (6MWT), Chair Stand Test (CST), Timed Up & Go (TUG), Sock Test, Lift and Carry Test (LCT), and Car Task.
      • Almeida G.J.
      • Schroeder C.A.
      • Gil A.B.
      • Fitzgerald G.K.
      • Piva S.R.
      Interrater reliability and validity of the stair ascend/descend test in subjects with total knee arthroplasty.
      • Hardy S.E.
      • Perera S.
      • Roumani Y.F.
      • Chandler J.M.
      • Studenski S.A.
      Improvement in usual gait speed predicts better survival in older adults.
      ,
      • Gogia P.P.
      • Braatz J.H.
      • Rose S.J.
      • Norton B.J.
      Reliability and validity of goniometric measurements at the knee.
      ,
      • Piva S.R.
      • Teixeira P.E.
      • Almeida G.J.
      • et al.
      Contribution of hip abductor strength to physical function in patients with total knee arthroplasty.

      Patient-reported outcomes of physical function

      The WOMAC-PF is a valid, reliable, and responsive measure that consists of 17 items related to physical function. Each item is scored on a 5-point Likert-type scale with descriptors from 0 (no difficulty) to 4 (extreme difficulty). Higher scores indicate more functional limitations.
      • Bellamy N.
      • Buchanan W.W.
      • Goldsmith C.H.
      • Campbell J.
      • Stitt L.W.
      Validation study of WOMAC: a health status instrument for measuring clinically important patient relevant outcomes to antirheumatic drug therapy in patients with osteoarthritis of the hip or knee.
      ,
      • Bellamy N.
      • Kean W.F.
      • Buchanan W.W.
      • Gerecz-Simon E.
      • Campbell J.
      Double blind randomized controlled trial of sodium meclofenamate (Meclomen) and diclofenac sodium (Voltaren): post validation reapplication of the WOMAC Osteoarthritis Index.
      The Canadian Occupational Performance Measure (COPM) captures a participant’s satisfaction (COPM-S) and performance (COPM-P) on 5 self-selected activities. The COPM has good psychometrics and its scores range from 0 (low satisfaction/performance) to 10 (high satisfaction/performance).
      • Dedding C.
      • Cardol M.
      • Eyssen I.C.
      • Dekker J.
      • Beelen A.
      Validity of the Canadian Occupational Performance Measure: a client-centred outcome measurement.
      ,
      • Eyssen I.C.
      • Steultjens M.P.
      • Oud T.A.
      • Bolt E.M.
      • Maasdam A.
      • Dekker J.
      Responsiveness of the Canadian occupational performance measure.

      Patient-reported outcomes of psychosocial measures

      The Arthritis Self-Efficacy Scale (ASES) is a reliable and valid instrument consisting of 3 subscales: pain (5 items), function (9 items), and other symptoms (6 items). ASES ratings range from 10 (very uncertain) to 100 (very certain). The mean of each subscale is used to tally the final score, with lower scores indicating lower self-efficacy.
      • Lorig K.
      • Chastain R.L.
      • Ung E.
      • Shoor S.
      • Holman H.R.
      Development and evaluation of a scale to measure perceived self-efficacy in people with arthritis.
      The Tampa Scale for Kinesophobia has good psychometric properties and lists 17 statements that a participant rates from 1 (strongly disagree) to 4 (strongly agree). Higher scores indicate greater fear of movement.
      • Larsson C.
      • Hansson E.E.
      • Sundquist K.
      • Jakobsson U.
      Psychometric properties of the Tampa Scale of Kinesiophobia (TSK-11) among older people with chronic pain.
      The Beck Anxiety Inventory is a reliable and valid survey that lists 21 common symptoms of anxiety that participants rate from 0 (not at all) to 3 (severely). Higher scores indicate heightened anxiety.
      • Beck A.T.
      • Epstein N.
      • Brown G.
      • Steer R.A.
      An inventory for measuring clinical anxiety: psychometric properties.
      The 10-item Center for Epidemiologic Studies Depression Scale is a valid scale that lists 10 statements that participants rate from “rarely” to “all the time.” Lower scores signify more depressive symptoms.
      • Andresen E.M.
      • Malmgren J.A.
      • Carter W.B.
      • Patrick D.L.
      Screening for depression in well older adults: evaluation of a short form of the CES-D (Center for Epidemiologic Studies Depression Scale).
      Fear of falls is assessed by a positive or negative response to the question, “Are you afraid of falling?” Global Rating of Change (GRC) is a valid instrument used to assess perceptions of changes in health status 3 and 6 months after baseline. The GRC is a 15-point scale ranging from -7 (a very great deal worse) to +7 (a very great deal better).
      • Deyo R.A.
      • Centor R.M.
      Assessing the responsiveness of functional scales to clinical change: an analogy to diagnostic test performance.
      ,
      • Friscia L.A.
      • Morgan M.T.
      • Sparto P.J.
      • Furman J.M.
      • Whitney S.L.
      Responsiveness of self-report measures in individuals with vertigo, dizziness, and unsteadiness.

      Data analysis

      We used baseline data from the parent study to assess validity. We used t tests or χ2 tests to compare the characteristics of those able to complete the SRT (performers) and those who failed or refused to try the SRT (nonperformers).
      • Jewell D.V.
      Guide to evidence based physical therapist practice.
      Pearson correlations assessed validity based on the strength of the associations between the SRT scores and scores from the other clinical measures.
      • Yuan Y.C.
      Multiple imputation for missing data: concepts and new development.
      Pearson correlations between 0.2 and 0.5 were considered small, between 0.5 and 0.7 were considered moderate, and 0.76 or greater were considered strong relationships.
      • Jewell D.V.
      Guide to evidence based physical therapist practice.
      Anticipating that the strength of the correlations could be affected by the missing data from the SRT nonperformers, we used multiple imputations with nonignorable missingness
      • Yuan Y.C.
      Multiple imputation for missing data: concepts and new development.
      ,
      to impute missing data from nonperformers and then reran the correlations with imputed data. Demographic variables that were significantly different between performers and nonperformers (sex, body mass index, discharge location, days spent in rehabilitation, and number of comorbidities) were used to inform the multiple imputation procedure.
      To assess responsiveness, we used datasets from subjects who completed all clinical measures at baseline, 3 months, and 6 months. Change scores (follow-up minus baseline scores) were calculated for each clinical measure at 3 and 6 months. Standardized effect sizes (change scores divided by the standard deviation of the baseline score) and standardized response means (change scores divided by the standard deviation of the change scores) were used to assess internal responsiveness. Effect sizes of 0.2 were considered small, 0.5 were considered moderate, and 0.8 or larger were considered large.
      • Jewell D.V.
      Guide to evidence based physical therapist practice.
      The GRC was used as the external anchor for the indices of external responsiveness. Participants who rated their health status 4 or greater (at least moderately better) were considered improved and participants’ ratings less than 4 were considered unimproved.
      • Friscia L.A.
      • Morgan M.T.
      • Sparto P.J.
      • Furman J.M.
      • Whitney S.L.
      Responsiveness of self-report measures in individuals with vertigo, dizziness, and unsteadiness.
      ,
      • Beninato M.
      • Gill-Body K.M.
      • Salles S.
      • Stark P.C.
      • Black-Schaffer R.M.
      • Stein J.
      Determination of the minimal clinically important difference in the FIM instrument in patients with stroke.
      Guyatt’s responsiveness index was calculated using the change scores of improved minus the change scores of unimproved divided by the square root of 2 times the standard deviation at baseline.
      • Husted J.A.
      • Cook R.J.
      • Farewell V.T.
      • Gladman D.D.
      Methods for assessing responsiveness: a critical review and recommendations.
      Pearson correlation assessed the association of SRT change scores to perception of change in the GRC. Finally, the area under the receiver operating characteristic curve (AUC) with 95% confidence intervals assessed SRT’s ability to discriminate between the improved and unimproved, based on the GRC.
      • Deyo R.A.
      • Centor R.M.
      Assessing the responsiveness of functional scales to clinical change: an analogy to diagnostic test performance.
      ,
      • Husted J.A.
      • Cook R.J.
      • Farewell V.T.
      • Gladman D.D.
      Methods for assessing responsiveness: a critical review and recommendations.
      AUCs between 0.7 and 0.8 were considered acceptable, between 0.8 and 0.9 were considered excellent, and greater than 0.9 were considered outstanding discrimination.
      • Hosmer D.
      • Lemeshow S.
      Applied logistic regression.
      SAS version 9.4a was used for analysis. This study follows the Standards for Reporting of Cohort Studies statement.

      Results

      Of the 240 participants enrolled in the parent study, 180 performed the SRT (performers) at baseline and 60 did not (nonperformers) (fig 1). Compared with nonperformers, the performers were younger, had lower body mass index, lower proportion of women, fewer comorbidities, and were more likely to be discharged home after surgery (table 1). Performers had stronger hip abductors, knee extensors, and more knee flexion and extension ROM than nonperformers. However, differences in knee extension ROM on the surgical side were not remarkable (table 2). Performers had better scores than nonperformers on all performance-based and patient-reported outcomes (PRO) of physical function, except for COPM-S. Performers had better scores than nonperformers for ASES-function and fear of falling. Self-efficacy for pain, kinesophobia, anxiety, and depression did not differ between performers and nonperformers.
      Table 1Participant characteristics at baseline
      CharacteristicsPerformers (n=180)Nonperformers (n=60)
      Age, y (mean ± SD)
      Significant at <.01.
      68.4±5.874.1±7.2
      Women, n (%)
      Significant at <.01.
      100 (56)48 (80)
      Race, n (%)
       White152 (84)48 (80)
       Black28 (16)11 (18)
      BMI, kg/m2 (mean ± SD)
      Significant at <.01.
      30.2±5.133.6±6.5
      Education, n (%)
       High school55 (31)21 (35)
       College and postgraduate112 (62)35 (85)
       Other technical training13 (7)4 (7)
      Reason for total knee arthroplasty, n (%)
       Osteoarthritis172 (96)58 (97)
       Inflammatory arthritis/trauma8 (4)2 (3)
      Discharge displacement after total knee arthroplasty, n (%)
      Significant at <.01.
       Home160 (89)38 (63)
       Other20 (11)22 (37)
      No. of Comorbidities, mean ± SD
      Significant at <.01.
      4.24±1.804.78±1.98
      Self-reported health status
       Excellent/very good97 (54)29 (48)
       Good/fair83 (46)31 (52)
      NOTE. Values are presented as mean ± SD for continuous variables and as frequency (percentage) for categorical variables. Cumulative illness rating scale was for mild to moderate morbidity burden.
      Significant at <.01.
      Table 2Baseline characteristics of performers and nonperformers: physical impairments, performance-based, and self-reported measures
      CharacteristicsPerformers (n=180)Nonperformers (n=60)Mean

      Difference
      95% CI
      Performance-based measures
       Single-leg balance test, s
      Surgical
      Significant at ≤.0001.
      16.5±16.44.3±4.8-12.3-15.0 to 9.6
      Nonsurgical
      Significant at ≤.0001.
      17.6±17.14.6±4.9-13.0-15.8 to -10.2
       Timed Up and Go test, s
      Significant at ≤.0001.
      10.5±2.213±2.92.51.7-3.3
       30-second Sit-to-Stand, n
      Significant at ≤.0001.
      10.9±2.58.7±2.7-2.2-2.9 to -1.4
       Stair climbing test, s
      Significant at ≤.0001.
      19.9±8.431.4±11.311.58.3-14.6
       40-meter fast-paced walk test, m/s2
      Significant at ≤.0001.
      1.4±0.21.1±0.2-0.3-0.4 to -0.3
       4-meter walk test, s
      Significant at ≤.0001.
      3.9±0.64.8±0.90.90.7-1.2
       6-minute walk test, m
      Significant at ≤.0001.
      448.7±82.1315.5±72.9-133.2-156.7 to -109.7
      Physical impairments
       Knee flexion PROM, degrees
      Surgical
      Significant at ≤.0001.
      125.2±9.6118.7±12.3-6.5-9.9 to -3.0
      Nonsurgical
      Significant at ≤.0001.
      132.8±11.2123.6±11.9-9.2-12.5 to -5.8
       Knee extension PROM, deg
      Surgical-1.0±5.1-2.0±5.2-1.0-2.5 to 0.5
      Nonsurgical
      Significant at .001.
      1.9±4.5-0.3±5.4-2.2-3.8 to -0.7
       Hip abductor strength, kg
      Surgical
      Significant at ≤.0001.
      12.4±4.57.0±4.7-5.4-6.8 to -4.0
      Nonsurgical
      Significant at ≤.0001.
      12.8±5.07.1±4.7-5.7-7.2 to -4.2
       Knee extensor strength, N-m
      Surgical
      Significant at ≤.0001.
      103.9±37.783.9±29.4-20.0-29.7 to -10.3
      Nonsurgical
      Significant at ≤.0001.
      147.7±50.9116.9±43.2-30.8-45.7 to -15.8
      Self-reported physical function measures
       WOMAC-PF
      Significant at ≤.0001.
      19.1±7.225.1±7.46.03.9-8.1
       COPM
      Performance
      Significant at .01.
      3.9±1.33.3±1.3-0.6-1.0 to -0.2
      Satisfaction3.3±1.62.9±1.5-0.4-0.8 to 0.1
      Self-reported psychosocial measures
       Arthritis Self-Efficacy Scale
      Pain76.5±16.372.8±16.2-3.6-8.4 to 1.1
      Function
      Significant at ≤.0001.
      85.7±11.674.2±13.5-11.5-15.0 to -7.9
      Other symptoms82.3±14.378.4±13.9-3.8-8.0 to 0.3
       Tampa Scale for Kinesiophobia33.7±5.734.3±6.00.6-1.0 to 2.3
       Beck Anxiety Inventory3.4±3.73.7±3.70.3-0.8 to 1.3
       CESD-108.3±2.88.2±2.6-0.1-0.9 to 0.7
       Fear of falling, n (%)
      Significant at .001.
      82 (46)42 (70)0.240.11-0.38
      NOTE. Values are presented as mean ± SD unless otherwise indicated.
      Abbreviations: CI, confidence interval; CES-D10, Center for Epidemiologic Studies Depression Scale; COPM, Canadian Occupational Performance Measure; PROM, passive range of motion; WOMAC-PF, Western Ontario and McMaster Universities Osteoarthritis Index-Physical Function Subscale.
      Significant at .01.
      Significant at ≤.0001.
      Significant at .001.
      We observed significant correlations between SRT and lower extremity impairments (r=0.15-0.32) in all performance-based tests (r=0.33-0.52). ASES-function and fear of falls were associated with SRT scores. The strengths of the correlations using imputed SRT values for nonperformers were similar (ρ=0.18-0.33) to the correlations using only performers’ scores (table 3).
      Table 3Correlation of SRT with measures of physical and psychosocial measures
      MeasuresSRT Non-Imputed (n=180)SRT Imputed (n=240)
      Physical impairments
       Knee flexion PROM, deg
      Surgical0.16
      Significant at .05.
      0.18
      Nonsurgical0.32
      Significant at ≤.001.
      0.32
      Significant at .01.
       Knee extension PROM, deg
      Surgical0.15
      Significant at .05.
      0.13
      Nonsurgical0.22
      Significant at .05.
      0.19
      Significant at .05.
       Hip abductor strength, kg
      Surgical0.29
      Significant at .01.
      0.30
      Significant at ≤.001.
      Nonsurgical0.29
      Significant at .01.
      0.29
      Significant at ≤.001.
       Knee extensor strength, N-m
      Surgical0.28
      Significant at .01.
      0.29
      Significant at ≤.001.
      Nonsurgical0.29
      Significant at ≤.001.
      0.30
      Significant at ≤.001.
      Performance-based measures
       Single-leg balance test, s
      Surgical SLB0.33
      Significant at ≤.001.
      0.35
      Significant at ≤.001.
      Nonsurgical SLB0.33
      Significant at ≤.001.
      0.34
      Significant at ≤.001.
       Timed Up and Go test, s-0.37
      Significant at ≤.001.
      -0.32
      Significant at .01.
       30-second Sit-to-Stand test, n0.33
      Significant at ≤.001.
      0.28
      Significant at ≤.001.
       Stair climbing test, s-0.39
      Significant at ≤.001.
      -0.35
      Significant at ≤.001.
       40-meter fast-paced walk, m/s20.52
      Significant at ≤.001.
      0.49
      Significant at ≤.001.
       4-meter walk test, s-0.43
      Significant at ≤.001.
      -0.38
      Significant at ≤.001.
       6-minute walk test, m0.52
      Significant at ≤.001.
      0.47
      Significant at ≤.001.
      Self-reported physical function measures
       WOMAC-PF-0.08-0.13
       Canadian Occupational Performance Measure
      Performance0.010.05
      Satisfaction-0.07-0.03
      Self-reported psychosocial measures
       Arthritis Self-Efficacy Scale
      Pain0.110.09
      Function0.34
      Significant at ≤.001.
      0.32
      Significant at ≤.001.
      Other symptoms0.090.09
       Tampa Scale for Kinesiophobia-0.02-0.01
       Beck Anxiety Inventory-0.01-0.01
       CES-D100.020.03
       Fear of falling-0.25
      Significant at .01.
      -0.22
      Significant at .05.
      NOTE. Values are presented as Pearson r correlations coefficient. SRT Imputed refers to Pearson correlations after multiple imputation with nonignorable missingness.
      Abbreviations: CES-D10, Center for Epidemiologic Studies Depression Scale; PROM, passive range of motion; SLB, single-leg balance; SRT, sitting-rising test; WOMAC-PF, Western Ontario and McMaster Universities Osteoarthritis Index-Physical Function Subscale.
      Significant at .05.
      Significant at ≤.001.
      Significant at .01.
      The responsiveness analysis included the total number of participants at 3 months (n=174) and 6 months (n=160) (see fig 1). The mean SRT score was -1.0±4.0 at baseline, 0.4±4.1 at 3 months, and 0.6±4.8 at 6 months (table 4). All outcome measures significantly improved over time, and there was wide variability in change scores for the outcome measures. Assessment of the SRT responsiveness at 3 and 6 months demonstrated small to moderate standard effect sizes (0.38, 0.42) and mean standardized response (0.38-0.37), small Guyatt index (0.25, 0.19), and Pearson correlations (r=-0.22 to -0.14). The AUC were 0.59 (95% CI, 0.49-0.69) at 3 months and 0.62 (95% CI, 0.52-0.73) at 6 months, which did not meet the acceptable level of discrimination. All other performance-based measures showed indices of responsiveness in the same ranges as the SRT. In contrast, the PROs of physical function showed large effect sizes (-1.2 to 2.1), small to moderate correlations with GRC (r=0.09-0.36), and did not reach the acceptable level to discriminative change (3mo-AUC, 0.59-0.63; 6mo-AUC, 0.59-0.71) (see table 4).
      Table 4Indices of responsiveness
      MeasuresNo.Mean ± SDΔSESSRMGIrAUC95% CI
      Sitting-rising test
       Baseline180-1.0±4.0
       3 mo1730.4±4.11.5±3.50.38
      Minimal effect size or small correlation.
      0.38
      Minimal effect size or small correlation.
      0.25
      Minimal effect size or small correlation.
      -0.22
      Minimal effect size or small correlation.
      0.590.49-0.69
       6 mo1600.6±4.81.7±4.30.42
      Minimal effect size or small correlation.
      0.37
      Minimal effect size or small correlation.
      0.19
      Minimal effect size or small correlation.
      -0.140.620.52-0.73
      Single-leg balance test–surgical, s
       Baseline24013.5±15.4
       3 mo22017.9±18.34.2±10.80.27
      Minimal effect size or small correlation.
      0.39
      Minimal effect size or small correlation.
      0.09-0.030.520.43-0.60
       6 mo19918.2±18.04.3±11.70.28
      Minimal effect size or small correlation.
      0.37
      Minimal effect size or small correlation.
      0.15-0.130.570.48-0.65
      Single-leg balance test–nonsurgical, s
       Baseline24014.3±16.0
       3 mo22016.7±17.62.1±11.50.130.18
      Minimal effect size or small correlation.
      -0.030.060.500.42-0.59
       6 mo19918.7±19.43.8±11.80.24
      Minimal effect size or small correlation.
      0.32
      Minimal effect size or small correlation.
      0.14-0.130.580.49-0.66
      Timed Up and Go test, s
       Baseline24011.2±2.6
       3 mo21910.2±2.2-0.9±1.6-0.36
      Minimal effect size or small correlation.
      -0.58
      Moderate effect size or correlation.
      -0.120.160.560.48, 0.64
       6 mo19910.1±2.1-1.0±1.7-0.39
      Minimal effect size or small correlation.
      -0.59
      Moderate effect size or correlation.
      -0.25
      Minimal effect size or small correlation.
      0.080.570.48, 0.67
      30-second Sit-to-Stand, n
       Baseline23610.3±2.7
       3 mo21712.3±3.21.9±2.20.69
      Moderate effect size or correlation.
      0.85
      Large effect size or high correlation.
      0.28
      Minimal effect size or small correlation.
      -0.28
      Minimal effect size or small correlation.
      0.590.51-0.67
       6 mo19712.4±3.22.0±2.30.73
      Moderate effect size or correlation.
      0.84
      Large effect size or high correlation.
      0.04-0.000.530.44-0.63
      Stair climbing test, s
       Baseline24022.8±10.5
       3 mo21818.6±8.26.5±6.5-0.38
      Minimal effect size or small correlation.
      -0.60
      Moderate effect size or correlation.
      -0.070.27
      Minimal effect size or small correlation.
      0.590.50-0.68
       6 mo19817.7±7.8-4.8±6.9-0.46
      Moderate effect size or correlation.
      -0.70
      Moderate effect size or correlation.
      -0.150.090.500.40-0.59
      40-meter fast-paced walk, m/s2
       Baseline2401.30±0.3
       3 mo1.4±0.3-2.2±3.7-0.29
      Minimal effect size or small correlation.
      -0.61
      Large effect size or high correlation.
      -0.010.25
      Minimal effect size or small correlation.
      0.550.47-0.63
       6 mo1.4±0.3-2.3±3.8-0.30
      Minimal effect size or small correlation.
      -0.61
      Moderate effect size or correlation.
      -0.19
      Minimal effect size or small correlation.
      0.130.590.51-0.68
      4-meter walk test, s
       Baseline2404.2±0.8
       3 mo2193.9±0.8-0.3±0.6-0.33
      Minimal effect size or small correlation.
      -0.44
      Minimal effect size or small correlation.
      -0.150.23
      Minimal effect size or small correlation.
      0.570.49-0.65
       6 mo1993.9±0.7-0.3±0.6-0.37
      Minimal effect size or small correlation.
      -0.53
      Moderate effect size or correlation.
      -0.28
      Minimal effect size or small correlation.
      0.150.610.52-0.70
      6-minute walk test, m
       Baseline240415.4±98.5
       3 mo217455.3±98.937.7±49.60.38
      Minimal effect size or small correlation.
      0.76
      Large effect size or high correlation.
      0.10-0.25
      Minimal effect size or small correlation.
      0.540.46-0.62
       6 mo199460.0±113.940.4±59.30.41
      Moderate effect size or correlation.
      0.68
      Moderate effect size or correlation.
      0.23
      Minimal effect size or small correlation.
      -0.18
      Minimal effect size or small correlation.
      0.630.54-0.71
      Western Ontario and McMaster Universities Osteoarthritis Index-Physical Function Subscale
       Baseline24020.6±7.7
       3 mo22111.3±7.4-9.1±7.6-1.19
      Large effect size or high correlation.
      -1.20
      Large effect size or high correlation.
      0.40
      Minimal effect size or small correlation.
      0.36
      Large effect size or high correlation.
      0.590.51-0.68
       6 mo22210.6±7.6-9.9±8.0-1.29
      Large effect size or high correlation.
      -1.24
      Minimal effect size or small correlation.
      -0.24
      Minimal effect size or small correlation.
      0.090.590.49-0.68
      Canadian Occupational Performance Measure-Performance Score
       Baseline2403.8±1.3
       3 mo2216.1±1.82.7±1.71.78
      Large effect size or high correlation.
      1.35
      Large effect size or high correlation.
      0.75
      Large effect size or high correlation.
      -0.30
      Large effect size or high correlation.
      0.630.54-0.70
       6 mo2226.5±1.82.8±1.82.11
      Large effect size or high correlation.
      1.56
      Large effect size or high correlation.
      0.74
      Large effect size or high correlation.
      -0.25
      Minimal effect size or small correlation.
      0.710.63-0.79
      Canadian Occupational Performance Measure-Satisfaction Score
       Baseline2403.2±1.6
       3 mo2215.9±2.02.7±2.21.70
      Large effect size or high correlation.
      1.22
      Large effect size or high correlation.
      0.81
      Large effect size or high correlation.
      -0.22
      Minimal effect size or small correlation.
      0.620.54-0.70
       6 mo2226.5±2.13.3±2.22.05
      Large effect size or high correlation.
      1.47
      Moderate effect size or correlation.
      ,
      Large effect size or high correlation.
      0.65
      Moderate effect size or correlation.
      -0.25
      Minimal effect size or small correlation.
      0.680.60-0.76
      NOTE. Δ represents change scores=follow-up SRT score–baseline SRT score (presented as mean ± SD). SES, standardized effect size=Δ/baseline SD. SRM, mean standard response=Δ/Δ SD. GI, Guyatt Responsiveness Index=Δ/√2(baseline SD), where Δ=mean change score among GRC responders–the mean change score of GRC nonresponders. r=Pearson correlations coefficient of the change scores with the Global Rating of Change.
      Abbreviation: AUC, area under the receiver operating characteristics curve.
      Minimal effect size or small correlation.
      Moderate effect size or correlation.
      Large effect size or high correlation.

      Discussion

      To our knowledge, this is the first study to assess SRT’s validity and responsiveness in individuals after TKA. The results generally support the SRT as a valid assessment tool in this population. SRT scores converged with all performance-based tests and diverged from most of the psychosocial measures. SRT scores did not associate with PROs of physical function. Results also suggest that the SRT’s responsiveness, while limited, is comparable to other commonly used performance-based tests after TKA. This study adds credence that the SRT is a valid test that does not require expensive technology and is practical for use by busy clinicians who need a biomechanically demanding activity to assess high levels of functional performance in patients after TKA.
      Ng et al
      • Ng S.S.
      • Fong S.S.
      • Chan W.L.
      • et al.
      The sitting and rising test for assessing people with chronic stroke.
      reported similar significant correlations between the SRT and measures of balance and ankle dorsiflexion strength in patients 8 years after stroke. However, they found that other measures of physical function did not correlate with the SRT, which could be explained by the small sample size (n=30) and use of different outcome measures. The Fugl-Meyer and Berg Balance Scale demonstrated small but not significant associations (r=0.20-0.32) with SRT. On the other hand, 5 Times Sit-to-Stand and the timed Up and Go tests demonstrated no association with the SRT. The authors speculated this lack of association could be a result of the complexity of the SRT compared with the other performance-based tests.
      • Ng S.S.
      • Fong S.S.
      • Chan W.L.
      • et al.
      The sitting and rising test for assessing people with chronic stroke.
      The SRT demands high levels of muscle strength, joint mobility, and balance, whereas most of the other performance-based tests used by Ng et al do not require these high levels of biomechanical demands. This may reflect the SRT’s ability to capture a unique aspect (ie, complexity) of the physical function construct.
      The lack of association noted between SRT scores and PROs of physical function agree with several post-TKA studies that reported similar findings between the WOMAC-PF and performance-based tests.
      • Donnelly C.
      • Carswell A.
      Individualized outcome measures: a review of the literature.
      • Walsh D.A.
      • Kelly S.J.
      • Johnson P.S.
      • Rajkumar S.
      • Bennetts K.
      Performance problems of patients with chronic low-back pain and the measurement of patient-centered outcome.
      • Persson E.
      • Rivano-Fischer M.
      • Eklund M.
      Evaluation of changes in occupational performance among patients in a pain management program.
      • Disantis A.Y.
      • Piva S.R.
      • Irrgang J.J.
      Standardized patient reported outcomes do not capture functional deficits of patients following contemporary total knee replacement: descriptive study.
      These studies suggest the lack of association may stem from the detrimental effect pain has on patients’ perceptions of abilities; that is, reduced knee pain after TKA promotes an inflated perception of good mobility.
      • White D.K.
      • Master H.
      Patient-reported measures of physical function in knee osteoarthritis.
      ,
      • Terwee C.B.
      • van der Slikke R.M.
      • van Lummel R.C.
      • Benink R.J.
      • Meijers W.G.
      • de Vet H.C.
      Self-reported physical functioning was more influenced by pain than performance-based physical functioning in knee-osteoarthritis patients.
      Additionally, emerging evidence suggests that WOMAC-PF underrepresents the more physically demanding functional activities identified as important by patients at later stages after TKR, such as kneeling, walking up and down hills and curbs, and transfers to and from the floor.
      • Disantis A.Y.
      • Piva S.R.
      • Irrgang J.J.
      Standardized patient reported outcomes do not capture functional deficits of patients following contemporary total knee replacement: descriptive study.
      The dissociations with the COPM is intriguing because 59% of participants selected activities in the COPM that require sitting on the floor (eg, gardening). Of these, 38% specifically selected floor sitting and rising as one of the 5 most relevant limited activities, a finding that supports the face value of the SRT test. The lack of associations maybe a result of the heterogeneity in scaling difficulty in SRT versus COPM.
      • Jolles B.M.
      • Buchbinder R.
      • Beaton D.E.
      A study compared nine patient-specific indices for musculoskeletal disorders.
      ,
      • Nieuwenhuizen M.G.
      • de Groot S.
      • Janssen T.W.
      • van der Maas L.C.
      • Beckerman H.
      Canadian Occupational Performance Measure performance scale: validity and responsiveness in chronic pain.
      Although we hypothesized that the SRT scores would diverge from all psychosocial measures, the significant associations with ASES-function and fear of falls do not necessarily dispute the validity of the SRT. Previous studies have questioned whether the ASES-function subscale evaluates self-efficacy, actual performance, or a combination of both.
      • Lorig K.
      • Chastain R.L.
      • Ung E.
      • Shoor S.
      • Holman H.R.
      Development and evaluation of a scale to measure perceived self-efficacy in people with arthritis.
      ,
      • Brady T.J.
      Measures of self-efficacy: Arthritis Self-Efficacy Scale (ASES), Arthritis Self-Efficacy Scale-8 Item (ASES-8), Children's Arthritis Self-Efficacy Scale (CASE), Chronic Disease Self-Efficacy Scale (CDSES), Parent's Arthritis Self-Efficacy Scale (PASE), and Rheumatoid Arthritis Self-Efficacy Scale (RASE).
      Although fear of falling was classified as a psychological construct for analysis, it makes sense clinically that subjects fearful of falling perform poorly in the SRT.
      The SRT scores in our study (-1.0±4.0 at baseline) are considerably lower than previously reported. Brito et al
      • Brito L.B.
      • Ricardo D.R.
      • Araujo D.S.
      • Ramos P.S.
      • Myers J.
      • Araujo C.G.
      Ability to sit and rise from the floor as a predictor of all-cause mortality.
      used a sample of healthy older adults and reported SRT scores ranging from 6 to 7.5 for the subgroup aged 63±7.4 years and 3.5 to 5.5 for an older subgroup 67±7.8 years of age. Ng et al
      • Ng S.S.
      • Fong S.S.
      • Chan W.L.
      • et al.
      The sitting and rising test for assessing people with chronic stroke.
      reported a mean SRT of 6.3±1.7 in poststroke participants. Multiple factors may explain these lower SRT scores. Our participants were older (69y vs 63y and 62y in the studies by Brito et al and Ng et al), more obese (30 kg/m2 vs 27 kg/m2 and 25 kg/m2 in the studies by Brito et al and Ng et al), probably experienced apprehension to engage the surgical knee during the performance of the SRT because of previous TKA surgery, and had more comorbidities (mean ± SD, 4.2±1.8) than the studies that excluded patients with musculoskeletal diseases.
      • Brito L.B.
      • Ricardo D.R.
      • Araujo D.S.
      • Ramos P.S.
      • Myers J.
      • Araujo C.G.
      Ability to sit and rise from the floor as a predictor of all-cause mortality.
      The magnitude of the indices of internal and external responsiveness of the SRT was similar to the other commonly used post-TKA performance-based tests. However, the PROs demonstrated higher internal responsiveness than the performance-based tests, which was a result of the lesser variability for the PROs change scores (coefficients of variation, -0.83 to 0.80 for changes in PROs; -1.78 to 5.48 for changes in functional performance tests). Both performance-based tests and PROs demonstrated similar external responsiveness and limited ability to discriminate improvers from nonimprovers.

      Study limitations

      Performing the SRT at baseline and at follow-up visits was voluntary and, on average, 25% of participants did not complete the test. To deal with this problem, we examined the correlation between SRT scores and clinical measures using multiple imputation procedures, which resulted in similar association strengths and validated the study results. We also had plans to derive thresholds of clinically important differences if the SRT AUCs demonstrated good discrimination between those who improved versus those who did not. However, due to poor discriminatory ability, this was not done.

      Conclusions

      SRT is a simple test that may enable clinicians to capture relevant information about the complex and demanding activity of sitting and rising from the floor after TKA. The moderate associations with other performance-based tests support its validity and suggest that the SRT measures a construct not captured by other tests. Although the responsiveness of the SRT did not reach an acceptable level of discrimination, it is comparable to other commonly used performance-based tests after TKA.

      Supplier

      • a.
        SAS; SAS Institute, Inc.

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