Abstract
Objective
Outcome expectancy is recognized as a determinant of exercise engagement and adherence. However, little is known about which factors influence outcome expectations for exercise among people with knee osteoarthritis. This is the first study to examine the association of outcome expectations for exercise with demographic, physical and psychosocial outcomes in individuals with knee osteoarthritis.
Methods
We performed a cross-sectional analysis of the baseline data from a randomized trial of Tai Chi versus physical therapy in participants with symptomatic knee osteoarthritis. Knee pain was evaluated using the Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index. Outcome expectations for exercise, self-efficacy, depression, anxiety, stress, and social support were measured using standard instruments. Logistic regression models were utilized to determine associates of outcome expectations.
Results
There were 262 participants with a mean age of 59.8 years, BMI 32.1 kg/m2, 69.1% female, 51.5% white, mean disease duration 8.6 years, and mean WOMAC knee pain and function scores of 260.8 and 906.8, respectively. Higher outcome expectations for exercise were associated with greater self-efficacy (odds ratio [OR] 1.25, 95% confidence interval [95% CI] 1.11–1.41; P=0.0004) as well as with less depressive symptoms (OR 0.84 for each 5-point increase, 95% CI 0.73–0.97; P=0.01). Outcome expectancy was not significantly associated with gender, race, education, pain, function, radiographic severity, social support, anxiety, or stress.
Conclusions
Our results suggest significant associations between outcome expectations for exercise and self-efficacy and depression. Future studies should examine how these relationships longitudinally affect long-term clinical outcomes of exercise-based treatment for knee osteoarthritis.
Keywords: osteoarthritis, outcome expectations, self-efficacy, exercise
Introduction
Knee osteoarthritis (OA) is a progressive joint disease and a leading contributor to pain and functional disability. A large volume of literature has shown that exercise reduces pain and improves physical function in people with knee OA, with benefits extending even to those with severe disease (1). Accordingly, a vast majority of guideline recommendations, including those from the American College of Rheumatology, support exercise as a key intervention in the physical management of OA (2-4). Despite the evidence-based benefits and collective efforts to promote physical activity among people with knee OA, exercise implementation remains a considerable challenge in this population. High quality evidence from a recent meta-analysis demonstrated that only 13% of individuals with knee OA met physical activity guidelines (5). Thus, there is a pressing demand to identify the factors that influence exercise behavior among the knee OA population.
Exercise engagement and adherence in people with knee OA may be determined, in part, by the formulation of perceived benefits also known as outcome expectations. Viewed from the social-cognitive framework, individuals decide which course of action to undertake based on personal beliefs and expect pursued activities to produce desired outcomes (6). The degree of perceived physical and psychological benefits of exercise could positively or negatively influence behavior such that an individual with higher outcome expectations would be more motivated to exercise compared to someone with less perceived benefits (7, 8). The influence of outcome expectancy on physical activity is supported by a growing body of empirical evidence across different populations (9, 10) and holds true in the context of chronic pain conditions (11, 12) including osteoarthritis. A recent study of individuals with hip OA enrolled in an exercise program found that outcome expectations played a major role among participants choosing to continue physical activity (13). Similarly, in a study evaluating the efficacy of exercise on reduction of knee pain from osteoarthritis, participants who reported higher outcome expectations had greater motivation to maintain exercise (14). Despite the substantial evidence supporting the predictive role of outcome expectancy, there is a poor understanding of the personal characteristics affecting this construct among people with knee OA.
The relationships surrounding outcome expectations for exercise in individuals with knee OA remain largely elusive; however, several qualitative studies have proffered associated themes. Among adults with knee pain, perceived benefits of exercise appeared to be shaped by significant others or healthcare professionals, past experiences, and uncertainty regarding the role of exercise (15). Additionally, varying objective opinions regarding exercise benefits appointed to different levels of radiographic severity suggested that expectations may depend on perceptions of disease activity. Disease-specific factors such as pain and functional limitations have also been shown to influence perceived negative outcomes for exercise in adults with arthritis (16). Although these emergent themes shed light on possible factors, no study has directly tested the associates of outcome expectations for exercise in people with knee OA.
Recently, exploring variables in relation to outcome expectations has been targeted in an effort to understand exercise behavior and strengthen theoretical frameworks for improving physical activity. Research has identified factors including mental health, self-efficacy, fear of falling, and disease knowledge (9, 10). Relationships to demographic variables such as race and gender have not been consistently demonstrated (7, 17-23), although some evidence suggests that higher education levels may be related to greater outcome expectations for exercise (24). Far less is known about these influential factors in individuals with knee OA. Identifying well-defined associates of outcome expectancy will provide insights for designing interventions to optimize exercise participation. Furthermore, the potential malleability of identified psychosocial relationships may have therapeutic implications. Therefore, we aimed to evaluate the associations between baseline outcome expectations for exercise and demographic, physical, and psychosocial factors in people with knee OA. We hypothesized that better psychosocial health (higher self-efficacy and social support; lower levels of depression, stress, and anxiety), lower disease severity (less pain and radiographic severity; higher physical function), and higher education levels would be positively associated with higher outcome expectations for exercise. We posed no a priori hypotheses on the association between outcome expectations and race or gender.
Methods
Study design
This study is a cross-sectional, secondary analysis of data obtained at baseline assessment from a single-center, randomized comparative effectiveness trial of Tai Chi versus a physical therapy regimen for participants with symptomatic knee OA. The study was approved by the Institutional Review Board of the Tufts Medical Center and was completed in September 2014. Signed informed consent was obtained from all study participants. A detailed study protocol has been published (25).
Recruitment procedures
We employed various advertising strategies to ensure enrollment of a diverse study population and queried the rheumatology clinic patient database. Interested respondents received standardized information pertaining to the study and underwent preliminary screening by telephone which encompassed questions about eligibility whose predictive values for knee OA were established from population-based data (26). Potentially eligible subjects who reported a diagnosis of knee OA and who had no obvious contraindications were invited to attend a formal screening visit at the clinic.
Eligibility criteria
Inclusion criteria at the preliminary screening include: (1) age 40 years and older with a prior diagnosis of knee OA and (2) pain on more than half the days of the past month during at least one of the following activities: walking, going up or down stairs, standing upright, or lying in bed at night. Exclusion criteria include: (1) prior experience with Tai Chi, physical therapy (PT) or similar types of exercise in the past 1 year; (2) serious medical conditions limiting the ability and safety to participate in the trial; (3) any intraarticular steroid injections in the previous 3 months or reconstructive surgery on the affected knee; (4) any intra-articular hyaluronic acid injections in the previous 6 months; (5) enrollment in any other clinical trial within the last 30 days; (6) plan to permanently relocate from the region during the trial period; and (7) not English-speaking.
Screening procedures
A study rheumatologist reviewed and confirmed the eligibility of participants. All participants met American College of Rheumatology criteria confirming symptomatic and radiographic knee OA (defined as the presence of a definite osteophyte in the tibiofemoral compartment and/or the patellofemoral compartment, as assessed on standing anterior/posterior and lateral or sunrise views). All participants who attended the screening visit and completed the Outcome Expectations for Exercise Scale and at least one other measure of interest were included in this analysis. Participants did not know to which group they would be randomized at the time of this visit.
Measures
Outcome expectations
Outcome expectancy is the anticipation that a particular behavior will produce a desired outcome (6). The Outcome Expectations for Exercise Scale (OES) is a validated scale consisting of 9 questions to evaluate perceived physical and mental benefits of exercise (27). Each item is rated from 1 to 5 (1 = strongly disagree; 2 = disagree; 3 = neither agree nor disagree; 4 = agree; 5 = strongly agree). The total score was derived by taking the average of all responses (range of 1 to 5). Higher scores represent higher outcome expectations.
Self-efficacy
Self-efficacy is the conviction that one can execute a behavior required to produce a desired outcome (6). Participants’ confidence in their ability to manage symptoms of arthritis was assessed using the 8-item Arthritis Self-Efficacy Scale (ASES-8) (9). Each belief was rated on a 10-point Likert scale where 1 = very uncertain and 10 = very certain. The total score was the average of all responses. Higher scores indicate better self-efficacy.
Depression
The presence or severity of depressed mood was measured using the Beck Depression Inventory-II (BDI-II), a validated, self-report instrument that contains 21 items. The score was derived from summing the numerical ratings (range 0 to 63) with higher scores indicating greater severity of depression. BDI-II scores ranging from 0-13 represent minimal depression; scores from 14-19 are mild; scores from 20-28 are moderate; and scores from 29-63 represent severe depression (28).
Anxiety
Anxiety was measured using the Patient-Reported Outcomes Measurement Information System (PROMIS; www.nihpromis.org) Emotional Distress-Anxiety Short Form (version 1.0), a 7-item questionnaire based on a 5-point scale (1 = never; 2 = rarely; 3 = sometimes; 4 = often; and 5 = always). The total score was converted to a standardized T-score (range of 36 to 82) with higher scores indicating greater severity of anxiety.
Stress
Stress was measured with the Perceived Stress Scale (PSS), a 10-item self-report questionnaire. For each item, participants indicated how often they experienced the symptom, from never (0) to very often (4). The total score was the sum of the numerical rating for each response and ranged from 0 to 40 with higher scores indicating greater perceived stress (29).
Social support
Social support was evaluated with the Medical Outcomes Study Social Support Survey (MOS-SSS), a 19-item questionnaire devised to measure the perceived availability of functional support (30). For each item, the respondents were asked to indicate how often each type of support was available to them when needed on a 5-point scale (1 = none of the time; 2 = a little of the time; 3 = some of the time; 4 = most of the time; and 5 = all of the time). The total score was converted to a scale of 0 to 100, with higher scores reflecting greater social support.
Pain and functional limitations in knee osteoarthritis
Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) (version VA3.1) is a validated, self-administered visual analogue scale designed to evaluate knee and hip osteoarthritis (31). It consists of three separate subscales: pain (score range 0–500), stiffness (0–200), and physical function (0–1700), with higher scores indicating more severe disease. Knee pain was measured using the WOMAC pain subscale, which includes 5 items regarding pain at activity or rest experienced in the past 48 hours. Functional limitations were measured by using the WOMAC physical function subscale that includes 17 items pertaining to difficulty with knee and/or hip function experienced in the previous 48 hours. Scores of WOMAC subscales were reported as the sum of all items.
Radiographic severity of knee osteoarthritis
Knee radiographs in standing anteroposterior, lateral, and sunrise views were obtained at the initial screening examination. Tibiofemoral radiographic severity was determined for each knee compartment based on osteophyte formation, joint space width, and subchondral bone scleroses in accordance with the Kellgren-Lawrence scoring system (32).
Statistical Analysis
Descriptive statistics, including means and frequencies, were generated for participant characteristics and measures of interest. Incomplete surveys were excluded from analysis for the measures of interest. Outcome expectations for exercise were the primary outcome of interest. The Outcome Expectations for Exercise Scale (OES) variable was not normally distributed and skewed toward the higher range with a median of 4; therefore, assumptions of linear regression could not be met. We created a binary variable for OES (<4 vs. ≥4). Independent t-tests were used to test for differences in continuous measures between low (OES <4) and high outcome expectancy (OES ≥4) categories. Univariate logistic regression models were generated to assess the relationship between participant characteristics and high outcome expectations. All analyses were performed in SAS 9.4 (SAS Institute Inc., Cary, NC). A P-value of less than 0.05 was considered statistically significant.
Results
Baseline demographic and clinical characteristics
Table 1 provides baseline demographic, clinical, and psychosocial characteristics of the participants. The analysis included data obtained at baseline assessment from 262 participants with a mean age of 59.8 years, 69.1% female, 51.5% white, 45.4% with at least college-level education, and an average body mass index of 32.1 kg/m2. The mean duration of disease was 8.6 years, and the mean WOMAC pain and function scores were 260.8 and 906.8, respectively. Of 247 patients who had knee radiographs evaluated, 41 (16.6%) were rated Kellgren-Lawrence grade 4, 81 (32.8%) grade 3, and 125 (50.6%) grade 2 or lower. The mean Outcome Expectations for Exercise Scale (OES) score was 4.0.
Table 1.
Demographic, disease-related, and psychological characteristics of the participants
| Characteristic | N | Mean (SD) or n (%) |
|---|---|---|
| Age, years | 261 | 59.8 (10.5) |
| Gender, female | 262 | 181 (69.1%) |
| Race | 262 | |
| White | 135 (51.5%) | |
| Black | 91 (34.7%) | |
| Other | 36 (13.7%) | |
| Education | 262 | |
| High school or less | 50 (19.1%) | |
| Trade school or some college | 93 (35.5%) | |
| College | 53 (20.2%) | |
| Graduate school | 66 (25.2%) | |
| Body mass index kg/m2 | 259 | 32.1 (7.4) |
| Kellgren-Lawrence grade | 247 | |
| Grade 4 | 41 (16.6%) | |
| Grade 3 | 81 (32.8%) | |
| Grade ≤ 2 | 125 (50.6%) | |
| Duration of knee pain, years | 208 | 8.6 (10.9) |
| WOMAC pain subscale (0.0 – 500.0)a | 262 | 260.8 (99.5) |
| WOMAC function subscale (0.0 – 1700.0) a | 260 | 906.8 (350.1) |
| Outcome Expectations for Exercise Scale (1.0 – 5.0)a | 262 | 4.0 (0.8) |
| Arthritis Self-Efficacy Scale-8 (1.0 – 10.0)a | 262 | 6.2 (2.1) |
| Beck Depression Inventory-II (0.0 – 63.0)a | 256 | 7.9 (9.1) |
| PROMIS Distress-Anxiety Short Form, t-score (36.0 – 82.0)a | 262 | 50.1 (8.8) |
| Perceived Stress Scale (0.0 – 40.0)a | 261 | 13.2 (7.0) |
| MOS Social Support Survey (0.0 – 100.0)a | 257 | 66.6 (23.5) |
MOS, Medical Outcomes Study; PROMIS, Patient-Reported Outcomes Measurement Information System; WOMAC, Western Ontario and McMaster Universities Osteoarthritis Index.
Total scale range
Table 2 provides the descriptive statistics for each item in the OES questionnaire. The overall mean was 4.0 with a standard deviation of 0.8. Item means ranged from 3.6 to 4.2. Item 3 (“Makes me feel less tired”) had the lowest mean score of 3.6, whereas item 1 (“Makes me feel better physically”) and item 4 (“Makes my muscles stronger”) had the highest mean score of 4.2. Item response distributions showed modest variability with standard deviations ranging from 0.9 to 1.0.
Table 2.
Descriptions and statistics of Outcome Expectations for Exercise Scale (OES) itemsa
| Item | Description | No. | Mean | SD | Median |
|---|---|---|---|---|---|
| 1 | Makes me feel better physically | 262 | 4.2 | 1.0 | 4.0 |
| 2 | Makes my mood better in general | 261 | 4.1 | 1.0 | 4.0 |
| 3 | Makes me feel less tired | 262 | 3.6 | 1.0 | 4.0 |
| 4 | Makes my muscles stronger | 260 | 4.2 | 0.9 | 4.0 |
| 5 | Is an activity I enjoy doing | 262 | 3.7 | 1.0 | 4.0 |
| 6 | Gives me a sense of personal accomplishment | 261 | 4.0 | 0.9 | 4.0 |
| 7 | Makes me more alert mentally | 262 | 3.9 | 0.9 | 4.0 |
| 8 | Improves my endurance in performing my daily activities | 261 | 4.1 | 0.9 | 4.0 |
| 9 | Helps to strengthen my bones | 261 | 4.1 | 0.9 | 4.0 |
Scores range from 1 to 5, with 1 indicating low outcome expectations for exercise and 5 indicating high outcome expectations.
Associations between constructs and high outcome expectancy for exercise
Table 3 illustrates the associations between variables and high outcome expectancy for exercise. Patients with higher self-efficacy were more likely to have higher outcome expectations for exercise (ASES-8 odds ratio [OR] 1.25, 95% confidence interval [95% CI] 1.11–1.41; P=0.0004). Individuals with a higher depressed mood as assessed by Beck Depression Inventory-II (BDI-II) were less likely to have higher outcome expectations (BDI-II OR 0.84 for each 5-point increase, 95% CI 0.73–0.97; P=0.01). Higher perceived stress (P=0.06) and female gender (P=0.08) were borderline significant and less likely to have higher outcome expectations. No other significant associations were found.
Table 3.
Associations between variables and high outcome expectancy category (OES ≥ 4.0)
| Variable | OR (95% CI) | p value |
|---|---|---|
| Gender | 0.08 | |
| Female | 0.62 (0.36, 1.07) | |
| Male | – | |
| Race | 0.91 | |
| White | – | |
| Black | 1.08 (0.51, 2.29) | |
| Other | 0.92 (0.54, 1.57) | |
| Education | 0.13 | |
| Graduate school | 1.41 (0.74, 2.71) | |
| College graduate | 1.47 (0.73, 2.96) | |
| Trade or some college | – | |
| High school or less | 0.64 (0.32, 1.28) | |
| Radiographic severity of tibiofemoral osteoarthritis | 0.12 | |
| Kellgren-Lawrence grade 4 | – | |
| Kellgren-Lawrence grade 3 | 0.70 (0.31, 1.58) | |
| Kellgren-Lawrence grade ≤ 2 | 0.48 (0.22, 1.02) | |
| WOMAC pain subscale (100 unit increase) | 0.97 (0.76, 1.25) | 0.84 |
| WOMAC function subscale (100 unit increase) | 0.97 (0.90, 1.04) | 0.41 |
| Arthritis Self-Efficacy Scale-8 (1 unit increase) | 1.25 (1.11, 1.41) | 0.0004 |
| Beck Depression Inventory-II (5 unit increase) | 0.84 (0.73, 0.97) | 0.01 |
| PROMIS Distress-Anxiety Short Form (5 unit increase) | 1.01 (0.88, 1.17) | 0.86 |
| Perceived Stress Scale (5 unit increase) | 0.84 (0.70, 1.01) | 0.06 |
| MOS Social Support Scale (10 unit increase) | 1.05 (0.94, 1.16) | 0.41 |
Difference in means of measures between low and high outcome expectancy categories
Table 4 illustrates the difference in means of continuous measures between low and high outcome expectations. A significant difference in mean ASES-8 score between the lower outcome expectancy group (5.6 ± 2.1) and higher outcome expectancy group (6.6 ± 2.1) was observed (P=0.0002). Patients with lower outcome expectations had a mean BDI-II score of 9.6 ± 10.7, as compared to 6.7 ± 7.7 in patients with higher outcome expectations (P=0.01). Perceived Stress Scale (PSS) was borderline significant (P=0.06).
Table 4.
Difference in means of measures between low and high outcome expectancy categoriesa
| Outcome expectancy category |
|||
|---|---|---|---|
| Measure | OES < 4.0 (N = 108) | OES ≥ 4.0 (N = 154) | p value |
| WOMAC pain subscale | 262.3 ± 106.6 | 259.7 ± 94.5 | 0.83 |
| WOMAC function subscale | 928.6 ± 341.5 | 891.9 ± 356.3 | 0.41 |
| Arthritis Self-Efficacy Scale-8 | 5.6 ± 2.1 | 6.6 ± 2.1 | 0.0002 |
| Beck Depression Inventory-II | 9.6 ± 10.7 | 6.7 ± 7.7 | 0.01 |
| PROMIS Distress-Anxiety Short Form | 50.0 ± 9.1 | 50.2 ± 8.6 | 0.86 |
| Perceived Stress Scale | 14.2 ± 7.5 | 12.5 ± 6.6 | 0.06 |
| MOS Social Support Survey | 65.2 ± 22.3 | 67.6 ± 24.3 | 0.42 |
Mean ± SD
Discussion
This is the first study to assess the previously unexamined relationships between baseline outcome expectations for exercise and psychosocial, disease-specific, and demographic factors in participants with knee OA. As we hypothesized, the findings indicated that higher outcome expectations were significantly associated with higher self-efficacy and less depressed mood. Male gender and lower perceived stress trended towards an association with higher outcome expectations but did not reach statistical significance. Education, race, anxiety, social support and disease-specific variables were not found to be significantly associated with outcome expectations.
We found that participants who reported higher outcome expectancy were significantly more likely to have stronger convictions in their ability to execute symptom management for knee OA. Defined as the belief in one's ability to execute a behavior required to produce a desired outcome, self-efficacy has been posited as a psychosocial construct operating in conjunction with outcome expectancy to influence behavior (33). In support of this theory, two cross-sectional studies demonstrated that higher outcome expectations for exercise were significantly related to greater self-efficacy (9, 10). Our study is the first to confirm this association in people with knee OA. Provided that outcome expectancy may influence physical activity in this population, assessing individual beliefs in both exercise benefits and symptom management would allow clinicians and researchers to characterize the degree of willingness to exercise. Furthermore, the incorporation of outcome expectancy and self-efficacy into risk stratification measures for non-adherence would benefit future trials of exercise-based interventions for people with knee OA.
Beyond the evaluation of outcome expectancy and self-efficacy, a number of studies have attempted to modify these constructs by employing social cognitive interventions (34). Physician-based activity counseling (35) and lifestyle interventions (36) demonstrated positive effects in strengthening both outcome expectancy and self-efficacy. Interestingly, healthcare professionals have been shown to influence outcome expectations for exercise in people with knee pain (15). Taken together, these findings suggest that physician counseling may have a significant impact on raising perceived benefits of exercise in the knee OA population, although this has not yet been studied. Future studies are warranted to verify the effects of physician counseling on modifying this psychosocial construct as well as to determine if such improvement could increase exercise engagement.
We also found that less depressed mood was significantly associated with higher outcome expectations. This finding adds to previous research suggesting that depressed individuals are more inclined to hold a pessimistic attitude about exercise outcomes (37, 38). Two studies confirmed an association of greater depressive symptoms with lower exercise expectations (39, 40). Depressed individuals tend to favor negative information and recall fewer positive experiences (41). This negative thinking may reduce outcome expectations for exercise (42). Moreover, research (43) indicates that depression poses a risk for motivational deficits characterized by the imbalance of negative (44) and positive outcome expectations (45). Provided that depressed individuals with knee OA are more likely to hold pessimistic beliefs towards exercise and be less willing to participate, future trials should assess the level of impact that reducing depressive symptoms may have on outcome expectancy in this population.
Participants with lower perceived stress tended to have higher outcome expectations, although this did not reach statistical significance. Stress was negatively associated with outcome expectancy in a study among people with knee OA (18). However, this study utilized an outcome expectation scale for a psychotherapeutic intervention. This suggests that outcome expectancy and its relationships with other psychosocial constructs could vary depending on intervention type. According to the social cognitive theory, past experience with a specific behavior influences the formulation of outcome expectancy (46). Thus, one may posit that perceptions of benefit are, to some degree, related to past experience with the form of intervention. As individuals with knee OA tend to be more familiar with exercise as opposed to other interventions such as cognitive behavioral therapy or surgery, there may be heterogeneity among outcome expectations and their respective associates. Future studies are warranted to elucidate upon the potential variations between outcome expectations for different interventions in people with knee OA.
We did not find an association between social support and outcome expectations for exercise. Previous studies similarly showed that social support was unrelated to outcome expectations for physical activity (7, 47). Contrastingly, a study of participants with knee OA undergoing cognitive behavioral therapy found that higher social support was significantly related to greater outcome expectations for treatment (18). The difference between these results may be attributable to varying perceptions regarding intervention type. Pretreatment anxiety was also not found to be associated with outcome expectations for exercise. This may be explained by the overall lower levels of reported anxiety as compared to the general population.
We did not find a significant association with outcome expectations for exercise and osteoarthritis-specific variables including pain, function, and radiographic severity at baseline. In agreement with our results, negative findings were reported in prior studies investigating expectation of benefit from different interventions for OA. Pain and physical function were not related to outcome expectancy in a trial of pain coping training in knee OA patients (18). Furthermore, in studies of patients scheduled for knee arthroplasty (48, 49), pre-surgical outcome expectancies were also not associated with WOMAC pain and function subscales. Interestingly, the emergent themes from a qualitative study suggest that arthritis-related symptoms such as pain and functional limitations may influence perceived negative outcomes for exercise (16). Additionally, in a survey conducted among people with knee pain, consensus regarding expectations of exercise benefit for radiographic knee OA decreased with disease severity (15). As these studies were conducted among community-dwelling adults, it is possible that disease-related factors may have less influence on outcome expectancy in people actively seeking exercise-based interventions.
No significant relationships were found between outcome expectations for exercise and gender, race, or education. Although male gender tended to have higher outcome expectations, statistical significance was not reached. Studies among other populations yielded conflicting results regarding gender. Collectively, male participants exhibited either stronger (21, 22) or weaker (7, 20) expectations for exercise, whereas remaining studies demonstrated no association (17-19, 23). The lack of influence of race has been generally consistent (18, 19) despite one study which reported that African Americans had higher levels of outcome expectations (7). Contrary to our hypothesis, we found no association between education level and outcome expectations for exercise. Among the limited literature, one study in adults with arthritis found that the average outcome expectations for exercise in their sample was below the normative value reported for similarly aged community-dwelling adults with a higher educational level (24). No relationship to education was found among adults with osteoporosis participating in an exercise program (10). Due to the collective lack of associations between race, gender, or education and outcome expectancy, it is unlikely that these demographic factors can predict or influence perceived benefits of exercise in the knee OA population.
Limitations
Study limitations should be considered. First, due to the cross-sectional nature of the study design, causal inferences cannot be drawn from the findings. Second, this investigation was performed among a population of people with knee OA seeking treatment and willing to participate in an exercise intervention. This may be reflected by the positively skewed OES score. Although small variations in outcome expectations were observed in this group, it is possible that a greater variation may occur among a more epidemiologic representation such as community-dwelling individuals with knee OA. This underscores the importance of identifying patients at risk of exercise non-adherence who may benefit from preemptive measures targeted at improving outcome expectations. Future research is required to compare outcome expectations among individuals with knee OA depending on their willingness to actively seek treatment.
Additionally, the subset of participants in this study was narrowed to those reporting to have greater frequency of pain following certain activities, which limited the ability to investigate expectations among a population with a wider spectrum of pain. Despite the association we identified between outcome expectations and mood, our population was not very depressed. It is unclear if the association would remain in a more depressed population. It is also important to note that this was a sample of patients specifically seeking treatment in the form of Tai Chi or physical therapy. Further research is urged to explore the perceptions of different forms of exercise such as mind-body therapy and how they may affect outcome expectancy among people with knee OA.
Despite these limitations, our analyses suggest that higher outcome expectations for exercise are associated with stronger self-efficacy and better mood. By discovering new and significant relationships, this study advances the current understanding of exercise beliefs among people with knee OA through psychosocial constructs and may aid and impact the design of future exercise trials. It is likely that individuals with weaker confidence in symptom management and with depressed mood may be more pessimistic about exercise and potentially less inclined to participate. These relationships may be useful for identifying subgroups at risk for non-adherence in both the clinical and research setting. Overall, prospective longitudinal studies are warranted to assess the impact of outcome expectations for exercise, self-efficacy, and depression on adherence and treatment outcomes in individuals with knee OA. Furthermore, research focus should be directed towards examining the malleability of these factors and their subsequent effect on exercise implementation.
Significance and Innovations.
This is the first study to examine the relationships between outcome expectations for exercise and demographic, physical, and psychosocial outcomes in individuals with knee osteoarthritis.
Participants with greater outcome expectations for exercise reported higher self-efficacy and better mood.
Identifying the factors that influence outcome expectations for exercise in persons with knee osteoarthritis is a key step for improving future trial design and treatment optimization.
Future longitudinal studies of exercise-based interventions are warranted to explore how outcome expectations for exercise in conjunction with self-efficacy and depression affect clinical outcomes in people with knee osteoarthritis.
Acknowledgments
Funding: The study was supported by the National Center for Complementary and Integrative Health (NCCIH) of the National Institutes of Health (R01AT005521 and K24 AT007323) and the National Center for Research Resources, National Institutes of Health (UL1RR025752) and the National Center for Advancing Translational Sciences, National Institutes of Health (UL1TR000073 and UL1TR001064). The contents of this manuscript are solely the responsibility of the authors and do not necessarily represent the official views of the NCCIH. The investigators are solely responsible for the content of the manuscript and the decision to submit for publication.
Footnotes
Disclosure: The authors declare no conflicts of interest.
References
- 1.Fransen M, McConnell S, Harmer AR, Van der Esch M, Simic M, Bennell KL. Exercise for osteoarthritis of the knee. Cochrane Database Syst Rev. 2015;1:CD004376. doi: 10.1002/14651858.CD004376.pub3. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Hochberg MC, Altman RD, April KT, Benkhalti M, Guyatt G, McGowan J, et al. American College of Rheumatology 2012 recommendations for the use of nonpharmacologic and pharmacologic therapies in osteoarthritis of the hand, hip, and knee. Arthritis care & research. 2012;64(4):465–74. doi: 10.1002/acr.21596. [DOI] [PubMed] [Google Scholar]
- 3.Osteoarthritis: national clinical guideline for care and management in adults. Royal College of Physicians; 2008. [PubMed] [Google Scholar]
- 4.Fernandes L, Hagen KB, Bijlsma JW, Andreassen O, Christensen P, Conaghan PG, et al. EULAR recommendations for the non-pharmacological core management of hip and knee osteoarthritis. Annals of the rheumatic diseases. 2013;72(7):1125–35. doi: 10.1136/annrheumdis-2012-202745. [DOI] [PubMed] [Google Scholar]
- 5.Wallis JA, Webster KE, Levinger P, Taylor NF. What proportion of people with hip and knee osteoarthritis meet physical activity guidelines? A systematic review and meta-analysis. Osteoarthritis Cartilage. 2013;21(11):1648–59. doi: 10.1016/j.joca.2013.08.003. [DOI] [PubMed] [Google Scholar]
- 6.Bandura A. Self-efficacy: The exercise of control. Freeman; New York: 1997. [Google Scholar]
- 7.Anderson ES, Wojcik JR, Winett RA, Williams DM. Social-cognitive determinants of physical activity: the influence of social support, self-efficacy, outcome expectations, and self-regulation among participants in a church-based health promotion study. Health Psychology. 2006;25(4):510. doi: 10.1037/0278-6133.25.4.510. [DOI] [PubMed] [Google Scholar]
- 8.Sallis JF, Johnson MF, Calfas KJ, Caparosa S, Nichols JF. Assessing perceived physical environmental variables that may influence physical activity. Res Q Exerc Sport. 1997;68(4):345–51. doi: 10.1080/02701367.1997.10608015. [DOI] [PubMed] [Google Scholar]
- 9.Lorig K, Chastain RL, Ung E, Shoor S, Holman HR. Development and evaluation of a scale to measure perceived self-efficacy in people with arthritis. Arthritis Rheum. 1989;32(1):37–44. doi: 10.1002/anr.1780320107. [DOI] [PubMed] [Google Scholar]
- 10.Resnick B, Nahm ES, Zhu S, Brown C, An M, Park B, et al. The impact of osteoporosis, falls, fear of falling, and efficacy expectations on exercise among community-dwelling older adults. Orthop Nurs. 2014;33(5):277–86. doi: 10.1097/NOR.0000000000000084. quiz 87-8. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 11.Goossens ME, Vlaeyen JW, Hidding A, Kole-Snijders A, Evers SM. Treatment expectancy affects the outcome of cognitive-behavioral interventions in chronic pain. Clin J Pain. 2005;21(1):18–26. doi: 10.1097/00002508-200501000-00003. discussion 69-72. [DOI] [PubMed] [Google Scholar]
- 12.Liddle SD, Baxter GD, Gracey JH. Chronic low back pain: patients' experiences, opinions and expectations for clinical management. Disabil Rehabil. 2007;29(24):1899–909. doi: 10.1080/09638280701189895. [DOI] [PubMed] [Google Scholar]
- 13.Hammer NM, Bieler T, Beyer N, Midtgaard J. The impact of self-efficacy on physical activity maintenance in patients with hip osteoarthritis - a mixed methods study. Disabil Rehabil. 2015:1–14. doi: 10.3109/09638288.2015.1107642. [DOI] [PubMed] [Google Scholar]
- 14.Damush TM, Perkins SM, Mikesky AE, Roberts M, O'Dea J. Motivational factors influencing older adults diagnosed with knee osteoarthritis to join and maintain an exercise program. J Aging Phys Act. 2005;13(1):45–60. doi: 10.1123/japa.13.1.45. [DOI] [PubMed] [Google Scholar]
- 15.Holden MA, Nicholls EE, Young J, Hay EM, Foster NE. Role of exercise for knee pain: What do older adults in the community think? Arthritis care & research. 2012;64(10):1554–64. doi: 10.1002/acr.21700. [DOI] [PubMed] [Google Scholar]
- 16.Wilcox S, Der Ananian C, Abbott J, Vrazel J, Ramsey C, Sharpe PA, et al. Perceived exercise barriers, enablers, and benefits among exercising and nonexercising adults with arthritis: results from a qualitative study. Arthritis Rheum. 2006;55(4):616–27. doi: 10.1002/art.22098. [DOI] [PubMed] [Google Scholar]
- 17.Ann Marie Spellbring PhD R. Understanding what motivates older adults to exercise. Journal of gerontological nursing. 2000;26(3):34. doi: 10.3928/0098-9134-20000301-08. [DOI] [PubMed] [Google Scholar]
- 18.Broderick JE, Junghaenel DU, Schneider S, Bruckenthal P, Keefe FJ. Treatment expectation for pain coping skills training: relationship to osteoarthritis patients' baseline psychosocial characteristics. Clin J Pain. 2011;27(4):315–22. doi: 10.1097/AJP.0b013e3182048549. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 19.Clark DO. Physical activity and its correlates among urban primary care patients aged 55 years or older. The Journals of Gerontology Series B: Psychological Sciences and Social Sciences. 1999;54(1):S41–S8. doi: 10.1093/geronb/54b.1.s41. [DOI] [PubMed] [Google Scholar]
- 20.Grembowski D, Patrick D, Diehr P, Durham M, Beresford S, Kay E, et al. Self-efficacy and health behavior among older adults. J Health Soc Behav. 1993;34(2):89–104. [PubMed] [Google Scholar]
- 21.Resnick B. A prediction model of aerobic exercise in older adults living in a continuing-care retirement community. Journal of Aging and Health. 2001;13(2):287–310. doi: 10.1177/089826430101300207. [DOI] [PubMed] [Google Scholar]
- 22.Resnick B, Palmer MH, Jenkins LS, Spellbring AM. Path analysis of efficacy expectations and exercise behaviour in older adults. Journal of advanced nursing. 2000;31(6):1309–15. doi: 10.1046/j.1365-2648.2000.01463.x. [DOI] [PubMed] [Google Scholar]
- 23.Resnick BM. Self-efficacy in geriatric rehabilitation. 1996 [Google Scholar]
- 24.Greene BL, Haldeman GF, Kaminski A, Neal K, Lim SS, Conn DL. Factors affecting physical activity behavior in urban adults with arthritis who are predominantly African-American and female. Phys Ther. 2006;86(4):510–9. [PubMed] [Google Scholar]
- 25.Wang C, Iversen MD, McAlindon T, Harvey WF, Wong JB, Fielding RA, et al. Assessing the comparative effectiveness of Tai Chi versus physical therapy for knee osteoarthritis: design and rationale for a randomized trial. BMC Complement Altern Med. 2014;14:333. doi: 10.1186/1472-6882-14-333. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 26.Rothfuss J, Mau W, Zeidler H, Brenner MH. Socioeconomic evaluation of rheumatoid arthritis and osteoarthritis: a literature review. Semin Arthritis Rheum. 1997;26(5):771–9. doi: 10.1016/s0049-0172(97)80044-3. [DOI] [PubMed] [Google Scholar]
- 27.Resnick B, Zimmerman SI, Orwig D, Furstenberg A-L, Magaziner J. Outcome Expectations for Exercise Scale Utility and Psychometrics. The Journals of Gerontology Series B: Psychological Sciences and Social Sciences. 2000;55(6):S352–S6. doi: 10.1093/geronb/55.6.s352. [DOI] [PubMed] [Google Scholar]
- 28.Beck AT, Steer RA, Brown GK. Manual for the beck depression inventory-II. Psychological Corporation; San Antonio, TX: 1996. [Google Scholar]
- 29.Cohen S, Kamarck T, Mermelstein R. A global measure of perceived stress. J Health Soc Behav. 1983;24(4):385–96. [PubMed] [Google Scholar]
- 30.Sherbourne CD, Stewart AL. The MOS social support survey. Soc Sci Med. 1991;32(6):705–14. doi: 10.1016/0277-9536(91)90150-b. [DOI] [PubMed] [Google Scholar]
- 31.Bellamy N. WOMAC osteoarthritis index: user guide IX. Nicholas Bellamy; 2008. [Google Scholar]
- 32.Kellgren JH, Lawrence JS. Radiological assessment of osteo-arthrosis. Annals of the rheumatic diseases. 1957;16(4):494–502. doi: 10.1136/ard.16.4.494. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 33.Bandura A. Social foundations of thought and action: A social cognitive theory. Prentice-Hall, Inc; 1986. [Google Scholar]
- 34.Williams DM, Anderson ES, Winett RA. A review of the outcome expectancy construct in physical activity research. Annals of Behavioral Medicine. 2005;29(1):70–9. doi: 10.1207/s15324796abm2901_10. [DOI] [PubMed] [Google Scholar]
- 35.Pinto BM, Lynn H, Marcus BH, DePue J, Goldstein MG. Physician-based activity counseling: intervention effects on mediators of motivational readiness for physical activity. Annals of Behavioral Medicine. 2001;23(1):2–10. doi: 10.1207/S15324796ABM2301_2. [DOI] [PubMed] [Google Scholar]
- 36.Dunn AL, Marcus BH, Kampert JB, Garcia ME, Kohl HW, Blair SN. Reduction in cardiovascular disease risk factors: 6-month results from ProjectActive. Preventive medicine. 1997;26(6):883–92. doi: 10.1006/pmed.1997.0218. [DOI] [PubMed] [Google Scholar]
- 37.Pomp S, Fleig L, Schwarzer R, Lippke S. Depressive symptoms interfere with post-rehabilitation exercise: outcome expectancies and experience as mediators. Psychol Health Med. 2012;17(6):698–708. doi: 10.1080/13548506.2012.661864. [DOI] [PubMed] [Google Scholar]
- 38.Vickers KS, Nies MA, Dierkhising RA, Salandy SW, Jumean M, Squires RW, et al. Exercise DVD improves exercise expectations in cardiovascular outpatients. Am J Health Behav. 2011;35(3):305–17. doi: 10.5993/ajhb.35.3.5. [DOI] [PubMed] [Google Scholar]
- 39.Sweet SN, Tulloch H, Fortier MS, Pipe AL, Reid RD. Patterns of motivation and ongoing exercise activity in cardiac rehabilitation settings: a 24-month exploration from the TEACH study. Annals of Behavioral Medicine. 2011;42(1):55–63. doi: 10.1007/s12160-011-9264-2. [DOI] [PubMed] [Google Scholar]
- 40.Vickers KS, Nies MA, Patten CA, Dierkhising R, Smith SA. Patients with diabetes and depression may need additional support for exercise. Am J Health Behav. 2006;30(4):353–62. doi: 10.5555/ajhb.2006.30.4.353. [DOI] [PubMed] [Google Scholar]
- 41.MacLeod AK, Pankhania B, Lee M, Mitchell D. Parasuicide, depression and the anticipation of positive and negative future experiences. Psychol Med. 1997;27(4):973–7. doi: 10.1017/s003329179600459x. [DOI] [PubMed] [Google Scholar]
- 42.Beck AT. Depression: Clinical, experimental, and theoretical aspects. University of Pennsylvania Press; 1967. [Google Scholar]
- 43.Kramer LV, Helmes AW, Seelig H, Fuchs R, Bengel J. Correlates of reduced exercise behaviour in depression: the role of motivational and volitional deficits. Psychol Health. 2014;29(10):1206–25. doi: 10.1080/08870446.2014.918978. [DOI] [PubMed] [Google Scholar]
- 44.Beck AT, Alford BA. Depression: Causes and treatment. University of Pennsylvania Press; 2009. [Google Scholar]
- 45.Maier SF, Seligman ME. Learned helplessness: Theory and evidence. Journal of experimental psychology: general. 1976;105(1):3. [Google Scholar]
- 46.Bolles RC. Reinforcement, expectancy, and learning. Psychological Review. 1972;79(5):394. [Google Scholar]
- 47.Resnick B, Orwig D, Magaziner J, Wynne C. The effect of social support on exercise behavior in older adults. Clinical Nursing Research. 2002;11(1):52–70. doi: 10.1177/105477380201100105. [DOI] [PubMed] [Google Scholar]
- 48.Sullivan M, Tanzer M, Reardon G, Amirault D, Dunbar M, Stanish W. The role of presurgical expectancies in predicting pain and function one year following total knee arthroplasty. Pain. 2011;152(10):2287–93. doi: 10.1016/j.pain.2011.06.014. [DOI] [PubMed] [Google Scholar]
- 49.Venkataramanan V, Gignac MA, Mahomed NN, Davis AM. Expectations of recovery from revision knee replacement. Arthritis Rheum. 2006;55(2):314–21. doi: 10.1002/art.21856. [DOI] [PubMed] [Google Scholar]