Determinants of Self-Report Outcome Measures in People With Knee Osteoarthritis

Functional improvement after unicompartmental knee replacement: a follow-up study with a performance based knee test

In literature no reports appear on functional recovery of unicompartmental knee replacement using both subjective and objective methods. Functional aspects are especially of importance, since prosthetic replacement is considered more often in younger patients, who require an optimal knee function for activities such as sports. In a prospective study on 38 patients with a mean age of 62.2 years functional improvement was measured. Using Knee Society Score (KSS) as a clinician based score and the Dynaport Knee Test as a functional test measurements were performed at preoperative, 3 and 6 months, 1 and 2 years, after surgery. The Dynaport Knee Test is an accelerometer-based system that objectively measures functional aspects of gait during various tasks of daily life. It consists of four sub scores. The KSS assesses pain and function. Both scores range from 0 to 100. The mean KSS preoperative was 44.0 and improved significantly to 81.7 at 3 months (P<0.001) and to 87.4 (P=0.025) at 6 months. No significant differences were noted after 6 months. The mean preoperative Dynaport Knee Test score was 35.8 and at 3 months 43.6 (P<0.001), 48.6 at 6 months (P<0.001). No significant differences were noted after 6 months follow-up. Of the Dynaport sub scores, the low demanding tasks Lift and Move and Locomotion, cease to improve beyond 6 months. The high demanding task Transfers only improved up to 3 months. However, the other high demanding tasks Rise and Descend showed improvement beyond 1 year after surgery, since the improvement from 6 months to 2 years was significant (P=0.023). This study has found that functional recovery continues beyond 6 months and even up to 2 years. It seems only more challenging tests can discriminate on improvement beyond a point where questionnaires cease to improve. The use of objective measurement methods is advocated next to the clinician based scores and self reported questionnaires.

Preoperative or postoperative self-efficacy: which is a better predictor of outcome after total hip or knee arthroplasty?

OBJECTIVE

Self-efficacy is considered an important determinant of outcome after total hip or knee arthroplasty. Aim of this study is to evaluate the contributions of preoperative and short-term postoperative self-efficacy in predicting long-term outcome.

METHODS

Self-efficacy was determined in 103 total hip and knee arthroplasty patients preoperatively and 6 weeks postoperatively with the Self-Efficacy for Rehabilitation Outcome Scale (SER). The 6-month outcome was assessed with a disease-specific and a generic self-report questionnaire and an objective measure of function (walking speed). Multiple linear regression analyses were used to examine the value of preoperative and short-term postoperative self-efficacy in predicting 6-month outcomes.

RESULTS

Preoperative self-efficacy was only a significant predictor of long-term postoperative walking speed, with higher self-efficacy resulting in faster walking speed at the long-term measurement (R(2)=0.47). Short-term postoperative self-efficacy was a significant predictor of the long-term postoperative generic outcome measure (physical functioning: R(2)=0.30; mental health: R(2)=0.53) and of walking speed (R(2)=0.66), with higher self-efficacy resulting in a better long-term outcome.

CONCLUSION

Short-term postoperative self-efficacy seems a better predictor of long-term outcome after total hip or knee arthroplasty than preoperative self-efficacy.

PRACTICE IMPLICATIONS

Interventions should focus on enhancing short-term postoperative rather than preoperative self-efficacy.

Measurement properties of the WOMAC LK 3.1 pain scale

OBJECTIVE

The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) is applied extensively to patients with osteoarthritis of the hip or knee. Previous work has challenged the validity of its physical function scale however an extensive evaluation of its pain scale has not been reported. Our purpose was to estimate internal consistency, factorial validity, test-retest reliability, and the standard error of measurement (SEM) of the WOMAC LK 3.1 pain scale.

METHOD

Four hundred and seventy-four patients with osteoarthritis of the hip or knee awaiting arthroplasty were administered the WOMAC. Estimates of internal consistency (coefficient alpha), factorial validity (confirmatory factor analysis), and the SEM based on internal consistency (SEM(IC)) were obtained. Test-retest reliability [Type 2,1 intraclass correlation coefficients (ICC)] and a corresponding SEM(TRT) were estimated on a subsample of 36 patients.

RESULTS

Our estimates were: internal consistency alpha=0.84; SEM(IC)=1.48; Type 2,1 ICC=0.77; SEM(TRT)=1.69. Confirmatory factor analysis failed to support a single factor structure of the pain scale with uncorrelated error terms. Two comparable models provided excellent fit: (1) a model with correlated error terms between the walking and stairs items, and between night and sit items (chi2=0.18, P=0.98); (2) a two factor model with walking and stairs items loading on one factor, night and sit items loading on a second factor, and the standing item loading on both factors (chi2=0.18, P=0.98).

CONCLUSION

Our examination of the factorial structure of the WOMAC pain scale failed to support a single factor and internal consistency analysis yielded a coefficient less than optimal for individual patient use. An alternate strategy to summing the five-item responses when considering individual patient application would be to interpret item responses separately or to sum only those items which display homogeneity.

Physical and Psychological Correlates of Disability among a Cohort of Individuals with Knee Osteoarthritis

While the physical correlates of knee osteoarthritis are well documented, less well documented are aspects of psychological functioning that may affect overall health and functional status. This paper describes the findings of a cross-sectional analysis that examined the strength of the relationship between selected psychological factors and the walking ability of adults with knee joint osteoarthritis. The variables assessed were pain, depression, levels of self-efficacy for pain and other-symptoms management, walking endurance, walking speed, and perceived exertion when walking. The sample, including 57 persons with unilateral and 43 persons with bilateral radiographic and symptomatic knee osteoarthritis, mean age, 69.9 ± 1 years, underwent standard assessment procedures on a single test occasion using several validated questionnaires and a series of walking tests on level ground. Bivariate and multiple regression analyses revealed that (a) higher pain and other-symptoms self-efficacy scores were associated with lower levels of pain (r= −0.29, −0.20.), perceived exertion during a walking task (r= −0.29, −0.31), and depression scores (r= −0.46, −0.54) (p< 0.001); (b) subjects with higher levels of self-efficacy for managing symptoms other than pain also recorded faster and fast speed walking velocities than those with lower self-efficacy scores (r= 0.30, 0.31) (p< 0.001); (c) self-efficacy for pain was the strongest predictor of pain intensity, and self-efficacy for symptom management was the strongest predictor of perceived exertion during walking, depression, and pain self-efficacy. Although no cause–effect relationship can be deduced from a cross-sectional analysis, these data imply that efforts to heighten self-efficacy for pain and other-symptoms management may influence the affective status, function, and effort-related perceptions of people with knee osteoarthritis quite significantly.

Modeling early recovery of physical function following hip and knee arthroplasty

BACKGROUND

Information on early recovery after arthroplasty is needed to help benchmark progress and make appropriate decisions concerning patient rehabilitation needs. The purpose of this study was to model early recovery of physical function in patients undergoing total hip (THA) and knee (TKA) arthroplasty, using physical performance and self-report measures.

METHODS

A sample of convenience of 152 subjects completed testing, of which 69 (mean age: 66.77 +/- 8.23 years) underwent THA and 83 (mean age: 60.25 +/- 11.19 years) TKA. Postoperatively, patients were treated using standardized care pathways and rehabilitation protocols. Using a repeated measures design, patients were assessed at multiple time points over the first four postoperative months. Outcome measures included the Lower Extremity Function Scale (LEFS), the physical function subscale of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC PF), the 6 minute walk test (6 MWT), timed up and go test (TUG) and a timed stair test (ST). Average recovery curves for each of the measures were characterized using hierarchical linear modeling. Predictors of recovery were sequentially modeled after validation of the basic developmental models.

RESULTS

Slopes of recovery were greater in the first 6 to 9 weeks with a second-degree polynomial growth term (weeks squared) providing a reasonable fit for the data over the study interval. Different patterns of recovery were observed between the self-report measures of physical function and the performance measures. In contrast to the models for the WOMAC PF and the LEFS, site of arthroplasty was a significant predictor (p = 0.001) in all of the physical performance measure models with the patients post TKA initially demonstrating higher function. Site of arthroplasty (p = 0.025) also predicted the rate of change for patients post THA and between 9 to 11 weeks after surgery, the THA group surpassed the function of the patients post TKA.

CONCLUSION

Knowledge about the predicted growth curves will assist clinicians in referencing patient progress, and determining the critical time points for measuring change. The study has contributed further evidence to highlight the benefit of using physical performance measures to learn about the patients' actual level of disability.

Role of knee kinematics and kinetics on performance and disability in people with medial compartment knee osteoarthritis

BACKGROUND

Although gait characteristics have been well documented in people with knee osteoarthritis, little is known about the relationships between gait characteristics and performance or disability. Our purpose was to examine the role of knee kinematics and kinetics on walking performance and disability in people with knee osteoarthritis. We also examined whether pain mediated the relationship between the knee adduction moment and performance or disability.

METHODS

Three-dimensional gait analysis was conducted on 54 people with medial compartment knee osteoarthritis. Performance was quantified with the Six Minute Walk test and disability was self-reported on the Short Form-36. The pain subscale of the Western Ontario McMaster Universities Osteoarthritis Index and the functional self-efficacy subscale of the Arthritis Self-Efficacy scale were completed.

FINDINGS

A step-wise linear regression demonstrated that the variance in Six Minute Walk test scores was explained by functional self-efficacy (50%) and the range of knee motion (8%). The variance in Short Form-36 was explained by pain (36%), the peak extension angle (19%) and the range of knee motion (4%). Pain was unrelated to the knee adduction moment so analyses of pain as a mediator of the adduction moment on either performance or disability were halted.

INTERPRETATION

Kinematic output from the motor control system is useful in understanding some variance in current performance and disability in people with knee osteoarthritis. The knee adduction moment was unrelated to these variables and pain did not mediate between the knee adduction moment and performance or disability. Therefore this moment does not explain current clinical status in people with knee osteoarthritis based on the measures of performance and disability used in this study.

Measuring quality of life in rheumatic conditions

Musculoskeletal disorders often have associated pain, functional impairment and work disability, and, not surprisingly, are the most common reasons for utilizing healthcare resources. Rheumatoid arthritis (RA) and fibromyalgia (FM) are causes of musculoskeletal pain and disability. Research indicates that there is a widespread impact of RA and FM on physical, psychological and social factors in affected individuals, and thus, outcome measures that encompass multiple aspects of quality of life are needed. Generic measures of quality of life identify associations between physical conditions and mental health and highlight the need to address psychological functioning to ultimately improve the individuals’ quality of life.

Performance measures provide assessments of pain and function in people with advanced osteoarthritis of the hip or knee

BACKGROUND AND PURPOSE

Pain and physical function are core outcome measures for people with osteoarthritis, and self-report questionnaires have been the preferred assessment method. There is evidence suggesting that self-reports of physical function represent what people experience when performing activities rather than their ability to perform activities. The purpose of this study was to examine the factorial validity of performance-specific assessments of pain and function.

SUBJECTS

The sample consisted of 177 participants who had osteoarthritis of the hip (n=81) or knee (n=96) and who were awaiting total joint arthroplasty.

METHODS

Through a cross-sectional design, participants performed 4 performance activities (self-paced walk test, stair test, Timed "Up & Go" Test, and Six-Minute Walk Test).

OUTCOMES

were time or distance (function) and pain ratings obtained immediately after each activity. The authors conceptualized 2 correlated factors, with pain items loading uniquely on 1 factor and functional items loading on the second factor, and uncorrelated error terms. Confirmatory factor analysis was applied.

RESULTS

Initial analysis yielded results consistent with the conceptualized model in this study with the exception of a nonzero correlation between the stair pain and function error terms. Dropping the stair test provided results consistent with the conceptualized model.

DISCUSSION AND CONCLUSION

Given the limitations of self-report alone as a method of obtaining reasonably distinct assessments of pain and function, the extent to which performance-specific assessments could accomplish this goal was examined in this study. It was found that collectively the walk test, Timed "Up & Go" Test, and Six-Minute Walk Test yielded 2 factors consistent with the health concepts of pain and function. The authors believe that the application of these tests may provide clinicians and clinical researchers with more distinct impressions of pain and function that complement information from self-report measures.

Activity limitations in the lower extremities in patients with osteoarthritis: the modifying effects of illness perceptions and mental health

OBJECTIVES

Using the International Classification of Functioning, Disability and Health as framework, we evaluated modifying effects of illness perceptions and mental health on the association between impairments in body structures and functions due to osteoarthritis (OA) and limitation in activities in the lower extremities.

METHODS

Self-reported limitation in activities was assessed by the Western Ontario and McMaster Universities OA index (WOMAC) function subscale in 316 patients with knee or hip pain or evidence of OA on knee or hip radiographs. Body structures and functions were evaluated during clinical and radiological assessments. Illness perceptions and mental health were assessed with the revised Illness Perception Questionnaire (IPQ-R) and the mental component summary score of the RAND 36-item Health Survey, respectively. For each patient an expected WOMAC function score was calculated, using an equation based on a multivariate model of the association of body structures and functions with limitation in activities.

RESULTS

The median (interquartile) self-reported WOMAC function score was 22.2 (9.6-43.5). Ninety-one patients reported more and 120 patients reported less limitation in activities than expected. Patients with lumbar spine degeneration, physical or exercise therapy and high IPQ-R identity, consequences and chronic timeline scores had an increased risk to report more limitation in activities than the expected range. Low IPQ-R identity, consequences and emotional representation scores and better mental health were associated with reporting less limitation in activities than the expected range.

CONCLUSION

Illness perceptions and mental health modify the association between self-reported limitation in activities and calculated limitation in activities based on impairments in body structures and functions due to OA.

The assessment of disability associated with osteoarthritis

PURPOSE OF REVIEW

Disability (activity limitation) is an important and common health outcome for patients with osteoarthritis, making accurate measures essential. This paper explores self-report measures of activity limitation associated with osteoarthritis and reports on recent conceptual advances that impact on the measurement of activity limitation.

RECENT FINDINGS

The Western Ontario and McMaster Universities Osteoarthritis Index and the Short Form-36, the most commonly used measures to assess activity limitation, continue to be validated in osteoarthritis. There has been little consensus, however, about which measure to use across different types of osteoarthritis. While new measures have been developed to assess activity limitation, it remains unclear whether or not these are an improvement over existing measures. The International Classification of Functioning, Disability and Health is becoming an important consideration. Commonly used measures do not map directly onto individual constructs of this classification, however a new measure for Japanese people with knee osteoarthritis was developed based on these constructs.

SUMMARY

There have been significant developments in the conceptual approach to measuring activity limitation. Measures are needed that operationalize activity limitation as defined by the International Classification of Functioning, Disability and Health (within or ideally across cultures), providing a common underlying construct for measures and hence facilitating comparability across studies.