Arthritis Care & Research Vol. 66, No. 12, December 2014, pp 1828 –1835 DOI 10.1002/acr.22402 © 2014, American College of Rheumatology

ORIGINAL ARTICLE

Factors Associated With Pain Experience Outcome in Knee Osteoarthritis JAMIE E. RAYAHIN,1 JOAN S. CHMIEL,2 KAREN W. HAYES,2 ORIT ALMAGOR,2 LAURA BELISLE,2 ALISON H. CHANG,2 KIRSTEN MOISIO,2 YUNHUI ZHANG,2 AND LEENA SHARMA2

Objective. Few strategies to improve pain outcome in knee osteoarthritis (OA) exist in part because how best to evaluate pain over the long term is unclear. Our objectives were to determine the frequency of a good pain experience outcome based on previously formulated OA pain stages and test the hypothesis that less depression and pain catastrophizing and greater self-efficacy and social support are each associated with greater likelihood of a good outcome. Methods. Study participants, all with knee OA, reported pain stage at baseline and 2 years. Baseline assessments utilized the Geriatric Depression Scale, Pain Catastrophizing Scale, Arthritis Self-Efficacy Scale, and Medical Outcomes Study social support survey. Using pain experience stages, good outcome was defined as persistence in or movement to no pain or stage 1 (predictable pain, known trigger) at 2 years. A multivariable logistic regression model was developed to identify independent predictors of a good outcome. Results. Of 212 participants, 136 (64%) had a good pain outcome and 76 (36%) a poor pain outcome. In multivariable analysis, higher self-efficacy was associated with a significantly higher likelihood of good outcome (adjusted odds ratio [OR] 1.14 [95% confidence interval (95% CI) 1.04 –1.24]); higher pain catastrophizing was associated with a significantly lower likelihood of good outcome (adjusted OR 0.88 [95% CI 0.83– 0.94]). Conclusion. This stage-based measure provides a meaningful and interpretable means to assess pain outcome in knee OA. The odds of a good 2-year outcome in knee OA were lower in persons with greater pain catastrophizing and higher in persons with greater self-efficacy. Targeting these factors may help to improve pain outcome in knee OA.

INTRODUCTION Knee osteoarthritis (OA) is a chronic, often progressive condition in the older population. Consequences of pain from knee OA include fatigue, sleep trouble, psychological stress, poorer perceived health, reduced activity, function decline, disability, and reduced independence (1). Pain is the most common reason for the decision to undergo total joint replacement. It is unclear how to evaluate the experience of pain over time in knee OA (1– 4). The change in pain intensity between baseline and followup, commonly used as an outcome, is difficult to interpret because of pain fluctuation in OA and individual adaptation to lessen Supported by the NIH/National Institute of Arthritis and Musculoskeletal and Skin Diseases (grant P60-AR-064464). 1 Jamie E. Rayahin, BS: University of Illinois, Chicago; 2 Joan S. Chmiel, PhD, Karen W. Hayes, PhD, Orit Almagor, MA, Laura Belisle, MPA, Alison H. Chang, PhD, Kirsten Moisio, PhD, Yunhui Zhang, MS, Leena Sharma, MD: Northwestern University, Chicago, Illinois. Address correspondence to Leena Sharma, MD, Division of Rheumatology, Feinberg School of Medicine, Northwestern University, 240 East Huron, M300, Chicago, IL 60611. E-mail: [email protected]. Submitted for publication March 4, 2014; accepted in revised form July 8, 2014.

1828

pain. Clinical observation suggests that the pattern of pain (whether it occurs only with use or also at rest and how predictable it is) often changes over time in knee OA. There is, however, no established outcome measure based on pain pattern. Using qualitative research that carefully evaluated meaningful aspects of the pain experience, Hawker et al (5) identified 2 types of pain in persons with hip or knee OA: 1) dull, aching pain that becomes more constant over time, punctuated increasingly with 2) short episodes of a more intense, often unpredictable, emotionally draining pain. The second type (not the first) resulted in avoidance of social and recreational activities. As noted by Hawker et al: “the inability to anticipate pain exacerbations appeared to result in substantial curtailing of participation in valued activities” (1). The authors formulated 3 pain stages (5): 1) early OA–stage 1, where pain is characterized by predictable sharp or other pain, usually brought on by a trigger (usually an activity, such as a sport) that eventually limits high impact activities, such as skiing, but had relatively little other impact; 2) mid OA–stage 2, where predictable pain is increasingly associated with unpredictable locking (knees) or other joint symptoms and the pain becomes more constant and begins to affect daily activities, such as walking and climbing stairs; and 3) advanced OA–stage 3,

Pain Experience Outcome in Knee OA

Significance & Innovations ●

Pain is notoriously difficult to evaluate over time in persons with knee osteoarthritis (OA). To our knowledge, this study is the first to use pain experience stages as a longitudinal outcome in a study of knee OA.

●

Developed by Hawker et al, the stages we applied to analyze pain over time comprehensively encapsulate aspects of pain that are not well represented in usual methods analyzing this outcome. Our findings provide evidence for the utility of these stages to assess pain experience outcome over time and will aid future longitudinal studies investigating pain in knee OA.

●

In addition, our findings provide longitudinal evidence that pain catastrophizing and self-efficacy are important targets to incorporate into strategies to help to prevent pain pattern from progressing in a distressing way, and which may in turn contribute to subsequent poor outcomes.

where constant dull/aching pain is punctuated by short episodes of often unpredictable intense pain that leaves one exhausted, and this pattern of intermittent, intense and often unpredictable hip or knee pain results in significant avoidance of activities, including social and recreational activities. To our knowledge, no previous study has used these stages to assess pain outcome in knee OA. Ultimately, if factors associated with a good pain outcome can be identified, they could become targets for strategies to help to prevent pain pattern from progressing in a distressing way and help to reduce the burden of the disease. Previous studies, mostly cross-sectional, have suggested that pain catastrophizing, self-efficacy, depression, and social support play an important role in the pain experience of knee OA. While a large number of studies in the literature describe the role of these factors in chronic pain and total joint replacement, less work has been done in knee OA. Pain catastrophizing has been defined as a set of pain-related cognitive and emotional processes, including helplessness, rumination, and magnification of threat value (6). Studies evaluating the association of pain catastrophizing with pain in knee OA (i.e., not total knee replacement) have been cross-sectional (7–10), with a recent exception (11). Self-efficacy was defined by Bandura (12) as the belief in one’s capacities to mobilize the internal resources and course of action needed to meet given situational demands. An association between self-efficacy and pain in knee OA has been demonstrated in crosssectional studies (13–15), but, to our knowledge, not in longitudinal studies. The preponderance of studies evaluating depression and pain in knee OA have also been cross-sectional (16 –21), with some exceptions (22–24). Social support, defined as the resources perceived as available from others in social networks, has been found to be

1829 associated with pain in knee OA in cross-sectional studies (25,26). A need for longitudinal knee OA studies has been emphasized to improve understanding of the evolution of pain (5) and of the effects of emotion-related variables on pain exacerbation (27). Our objectives were, in persons with knee OA, to determine the frequency of a good 2-year pain experience outcome, defined based upon pain stages, and test the hypothesis that less depression and pain catastrophizing and greater self-efficacy and social support at baseline are each associated with greater likelihood of a good 2-year pain experience outcome.

PATIENTS AND METHODS Sample. The study participants were members of a cohort of a natural history study of knee OA, the Mechanical Factors in Arthritis of the Knee-Study 3, recruited from the community via periodicals targeting older persons; neighborhood organizations; the Northwestern Buehler Center on Aging, Health, and Society registry; and medical center referrals. The inclusion criteria were definite tibiofemoral osteophyte presence (Kellgren/Lawrence [K/L] radiographic grade ⱖ2) in 1 or both knees and a Likert category of at least “a little difficulty” for ⱖ2 items in the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) physical function scale. The exclusion criteria were corticosteroid injection within the previous 3 months; history of avascular necrosis, rheumatoid or other inflammatory arthritis, periarticular fracture, Paget’s disease, villonodular synovitis, joint infection, ochronosis, neuropathic arthropathy, acromegaly, hemochromatosis, gout, pseudogout, osteopetrosis, or meniscectomy; or exclusion criteria for magnetic resonance imaging. Approval was obtained from the institutional review boards of Northwestern University and NorthShore University HealthSystem Evanston Hospital. Written consent was obtained from all participants. Measurement of pain catastrophizing, self-efficacy, depression, and social support. Pain catastrophizing was assessed using the Pain Catastrophizing Scale, a selfreported questionnaire that assesses cognitive and affective responses to pain with demonstrated validity and reliability (28,29). The participants indicated the degree to which they experienced specific thoughts or feelings while experiencing pain on a 5-point scale (higher score ⫽ worse). Function self-efficacy was assessed using the Arthritis Self-Efficacy Scale function subscale (self-rating of certainty in one’s ability to walk 100 feet in 20 seconds, walk 10 steps downstairs in 7 seconds, and get out of an armless chair without using hands for support [higher score ⫽ better]) (30). Construct and concurrent validity and test–retest reliability for the subscales have been demonstrated in persons with arthritis (30). Depression was assessed using the 15-item version of the Geriatric Depression Scale with demonstrated strong psychometric properties (31) and was defined as a score ⬎5 (31). Social support was assessed using the Medical Outcomes Study Social Support Survey (higher score ⫽ better), which rep-

1830 resents emotional/informational, tangible, affectionate, and positive social interaction dimensions of support (32). High convergent and discriminant validity of the items, construct validity, and reliability have been demonstrated in individuals with chronic conditions (32). Measurement of other variables. Body mass index (BMI) was calculated as weight in kg divided by height in meters squared. Knee extensor strength during movement (average peak torque corrected for body weight [Nm/kg]) was assessed isokinetically at 120°/second using a computer-driven isokinetic dynamometer (Biodex System 3) by a single tester. The value for the stronger knee was used in the analysis. Participants underwent bilateral anteroposterior weight-bearing knee radiographs at baseline in the semiflexed position with fluoroscopic confirmation of anterior and posterior tibial plateau line superimposition and tibial spine centering within the femoral notch (33). Disease severity was assessed using the following K/L system: 0 ⫽ normal; 1 ⫽ possible osteophytes; 2 ⫽ definite osteophytes, possible joint space narrowing; 3 ⫽ moderate osteophytes, definite joint space narrowing, some sclerosis, possible attrition; and 4 ⫽ large osteophytes, marked joint space narrowing, severe sclerosis, definite attrition. The value for the more diseased knee was used in the analysis. Comorbidity was assessed using a questionnaire adaptation of the Charlson Index (34). Back pain presence was defined by the answer to the following question: during the past 30 days have you had any back pain? Hip symptom presence was defined as a yes answer to the following question for either right or left hip: during the past 12 months, have you had pain, aching, or stiffness in your hip on most days of at least 1 month? Physical activity was assessed using the Physical Activity Scale for the Elderly (35). Medication use was defined as a yes answer to the following question: during the past 30 days, have you used any of the following medications for joint pain or arthritis on most days? (For at least 1 category among acetaminophen, nonprescription nonsteroidal antiinflammatory drugs (NSAIDs), prescription NSAIDs, and prescription pain medications). Assessment of pain experience outcome. At baseline and the 2-year followup, participants were asked to pick one of the following statements (using the pain stages of Hawker et al [5], modified slightly to full sentences and defining potentially unclear terms) that most closely matched their knee pain experience as it had usually been over the past 6 months: 1) I have no knee pain; 2) my pain is predictable (I know what brings it on) and usually sharp. It is usually brought on by a trigger (like an activity or movement) that has kept me from high impact activities, such as skiing, but has not had much other impact on my physical activities; 3) my predictable pain comes more and more with unpredictable (comes when I don’t expect it) locking of knees or other knee joint symptoms. The pain is becoming more constant and is affecting daily activities, such as walking and climbing stairs; and 4) my pain is constant, and is dull and aching. And, on top of this pain, I have short episodes of often unpredictable intense pain

Rayahin et al that leaves me feeling exhausted. Because of this pattern of pain, I am avoiding a lot of social and recreational activities. These statements were categorized as no pain, stage 1, stage 2, and stage 3, respectively. We determined test– retest reliability of pain stage reporting in 28 of our participants by administering the questionnaire on 2 occasions 1 month apart, finding excellent agreement (kappa coefficient using quadratic weighting: ␬ ⫽ 0.85 [95% confidence interval (95% CI) 0.75– 0.95]). Good pain outcome hinged upon predictability in the pain experience and was defined as baseline 3 2-year reports of (no pain or stage 1) 3 (no pain or stage 1) or (stage 2 or 3) 3 (no pain or stage 1). Poor outcome was (stage 2 or 3) 3 (stage 2 or 3) or (no pain or stage 1) 3 (stage 2 or 3). Statistical analysis. All analyses used the person as the unit of analysis. We first stratified the study participants into 2 groups based on the 2-year pain experience outcomes and compared baseline characteristics using 2-sample t-tests (for continuous variables) and chi-square tests (for categorical variables). To avoid inclusion of highly correlated variables that could result in harmful multicollinearity in the multivariable prediction models, we calculated Spearman’s correlation coefficients for continuous variable pairs. We then developed the multivariable prediction models using univariate logistic regression to estimate associations of each baseline variable separately with the outcome (good versus poor pain experience) and retaining those with a univariate P value less than or equal to 0.20 as potential predictors in the subsequent full multivariable logistic model. These results are summarized using odds ratios (ORs) and 95% CIs adjusted for the other variables in the model. As a sensitivity analysis, we also derived a multivariable logistic model that included all covariates, including those that did not meet our univariate P value screening threshold.

RESULTS Among 250 participants, 212 completed the 2-year followup evaluation. The reasons for not completing this evaluation included could not be reached (12 persons), serious medical condition (6 persons), too busy (5 persons), could not miss work (5 persons), and other reasons (10 persons). As shown in Table 1, the 212 participants had a mean ⫾ SD age of 64.6 ⫾ 10.1 years and a mean ⫾ SD BMI of 28.5 ⫾ 5.7 kg/m2; 163 participants (76.9%) were women. The baseline values for pain catastrophizing, selfefficacy, depression, social support, and covariables for participants belonging to each of the outcome groups are shown in Table 1. At baseline, 32 participants (15.1%) had no knee pain, 95 participants (44.8%) had stage 1 knee pain, 70 participants (33.0%) had stage 2 knee pain, and 15 participants (7.1%) had stage 3 knee pain. The participants who did not complete the study did not significantly differ in baseline age (mean ⫾ SD 66.9 ⫾ 11.1 years), sex (68% women), BMI (mean ⫾ SD 28.6 ⫾ 4.7 kg/m2), self-efficacy (mean ⫾ SD 23.9 ⫾ 5.6), social support (mean ⫾ SD 58.9 ⫾ 16.0), frequency of depression (present in only 2 of the 38

Pain Experience Outcome in Knee OA

Table 1.

1831

Baseline characteristics of all participants and good and poor 2-year pain experience outcome groups*

Baseline characteristics Pain catastrophizing score (higher score ⫽ worse) Self-efficacy score (higher score ⫽ better) Depression present, no. (%) Social support score (higher score ⫽ better) Age, years Women, no. (%) BMI, kg/m2 Knee extensor strength (stronger of right and left knee), Nm/kg K/L grade (worse of right and left knee), no. (%) 0–1 2 3 4 Comorbidity score Back pain, no. (%) Hip symptoms, no. (%) Physical activity score (PASE) Medication use, no. (%)

All participants (n ⴝ 212)

Good pain experience outcome (n ⴝ 136)

Poor pain experience outcome (n ⴝ 76)

6.6 ⫾ 7.0 25.5 ⫾ 5.2 5 (2.4) 57.3 ⫾ 16.1 64.6 ⫾ 10.1 163 (76.9) 28.5 ⫾ 5.7 104.6 ⫾ 29.3

4.3 ⫾ 4.7 27.1 ⫾ 3.5 2 (1.5) 58.0 ⫾ 16.4 65.7 ⫾ 10.1 107 (78.7) 27.1 ⫾ 4.6 108.6 ⫾ 28.0

10.6 ⫾ 8.5 22.8 ⫾ 6.4 3 (3.9) 55.9 ⫾ 15.2 62.7 ⫾ 10.0 56 (73.7) 31.1 ⫾ 6.6 97.6 ⫾ 30.4

23 (10.8) 103 (48.6) 34 (16.0) 52 (24.5) 1.0 ⫾ 1.7 155 (73.1) 89 (42.0) 154.6 ⫾ 83.5 95 (44.8)

16 (11.8) 77 (56.6) 18 (13.2) 25 (18.4) 0.8 ⫾ 1.4 93 (68.4) 56 (41.2) 152.8 ⫾ 73.5 52 (38.2)

7 (9.2) 26 (34.2) 16 (21.1) 27 (35.5) 1.5 ⫾ 2.2 62 (81.6) 33 (43.4) 157.8 ⫾ 99.4 43 (56.6)

P ⬍ 0.0001 ⬍ 0.0001 0.35 0.36 0.04 0.51 ⬍ 0.0001 0.01 0.0046

0.0072 0.055 0.86 0.71 0.015

* Values are the mean ⫾ SD unless indicated otherwise. P relates to the difference in baseline characteristic between the 2 outcome groups. Participants with a good 2-year pain experience outcome (versus participants with a poor outcome) in univariate analyses had lower/less pain catastrophizing, BMI, severe disease, comorbidity, and medication use and higher self-efficacy, strength, and age but did not differ in depression, social support, sex, back pain, hip symptoms, or self-reported physical activity. P for depressive symptoms as a continuous variable also exceeded 0.20. BMI ⫽ body mass index; K/L ⫽ Kellgren/Lawrence; PASE ⫽ Physical Activity Scale for the Elderly.

persons), or distribution of pain stage (18 persons [47.4%] stage 1, 15 persons [39.5%] stage 2, and 5 persons [13.2%] stage 3), but had worse pain catastrophizing (mean ⫾ SD 10.5 ⫾ 8.6; P ⫽ 0.01). Table 2 shows the correlations between continuous variables at baseline. Table 3 shows the frequency of 2-year pain stage by baseline pain stage. In total, 121 persons (57.1%) had no change in pain stage, 43 persons (20.3%) had worsening, and 48 persons (22.6%) had improvement. Overall, of the 212 participants, 136 persons (64.2%) had good pain experience outcome and 76 persons (35.8%) had poor pain experience outcome at the 2-year followup. As shown in Table 4, in the multivariable logistic regresTable 2.

sion model that adjusted for baseline factors meeting the criteria for inclusion, the odds of a good pain experience outcome were significantly higher with greater selfefficacy and significantly lower with greater pain catastrophizing. In the sensitivity analysis, when all covariables (i.e., those shown in Table 1) were included in the model, the results were similar (pain catastrophizing adjusted OR 0.88 [95% CI 0.82– 0.94] and self-efficacy adjusted OR 1.15 [95% CI 1.05–1.27]). Results were similar for each pain catastrophizing subscale score analyzed in separate fully adjusted models, namely, for rumination (adjusted OR 0.81 [95% CI 0.70 – 0.95]), magnification (adjusted OR 0.65 [95% CI 0.52– 0.83]), and helplessness (adjusted OR 0.74

Correlations between continuous variables at baseline (n ⴝ 212)*

Pain Social Depressive catastrophizing Self-efficacy support symptoms (higher score (higher score (higher score (higher score ⴝ worse) ⴝ better) ⴝ better) ⴝ worse) Pain catastrophizing Self-efficacy Social support Depressive symptoms Age BMI Extensor strength Comorbidity Physical activity

1.00

⫺0.41 1.00

⫺0.18 0.19 1.00

0.26 ⫺0.17 ⫺0.26 1.00

Age

BMI

⫺0.25 0.17 ⫺0.007 ⫺0.29 0.07 0.04 ⫺0.20 0.02 1.00 0.15 1.00

* Values are Spearman’s correlation coefficients for continuous baseline covariables. BMI ⫽ body mass index.

Extensor Physical strength Comorbidity activity ⫺0.17 0.43 ⫺0.02 ⫺0.02 ⫺0.22 ⫺0.34 1.00

0.06 ⫺0.15 0.10 ⫺0.05 0.09 0.18 ⫺0.22 1.00

⫺0.03 0.14 0.11 ⫺0.09 ⫺0.31 ⫺0.03 0.16 ⫺0.02 1.00

1832

Rayahin et al

Table 3. Pain experience stage at 2-year followup by pain experience stage at baseline (n ⴝ 212)* Pain experience stage at baseline

No pain

Stage 1

Stage 2

Stage 3

No pain Stage 1 Stage 2 Stage 3

17 (8.0) 8 (3.8) 4 (1.9) 1 (0.5)

11 (5.2) 66 (31.1) 26 (12.3) 3 (1.4)

4 (1.8) 18 (8.4) 33 (15.6) 6 (2.8)

0 (0.0) 3 (1.4) 7 (3.3) 5 (2.4)

* Values are the number (percentage) of persons at the given pain experience stage at the 2-year followup according to their pain experience stage at baseline.

[95% CI 0.63– 0.86]). In each of these models, self-efficacy was the only other variable significantly associated with the outcome.

DISCUSSION Participants with a good 2-year pain experience outcome (versus participants with a poor outcome) in univariate analyses had lower/less pain catastrophizing, BMI, severe disease, comorbidity, and medication use and higher selfefficacy, strength, and age but did not differ in depression, social support, sex, back pain, hip symptoms, or selfreported physical activity. In adjusted analyses, higher/ more pain catastrophizing was associated with signifiTable 4. Multivariable model for baseline to 2-year good pain experience outcome (dependent variable)* Independent variable at baseline Age, years Pain catastrophizing score (higher score ⫽ worse) Self-efficacy score (higher score ⫽ better) BMI, kg/m2 Extensor strength, (stronger of right and left), Nm/kg K/L grade (worse of right and left) versus 0–1 (ref.) K/L grade 2 K/L grade 3 K/L grade 4 Comorbidity score Back pain versus no back pain (ref.) Medication use versus no use (ref.)

Adjusted OR (95% CI) 1.04 (0.99–1.08) 0.88 (0.83–0.94) 1.14 (1.04–1.24) 0.93 (0.87–1.01) 0.998 (0.985–1.01)

2.13 (0.61–7.40) 0.31 (0.08–1.23) 0.41 (0.10–1.62) 0.83 (0.65–1.06) 0.58 (0.24–1.42) 0.75 (0.36–1.56)

* Values are the adjusted odds ratio (OR; 95% confidence interval [95% CI]) in the multiple logistic regression model, including baseline covariables meeting the criteria to be included (ORs adjusted for all other variables in the table). The dependent variable was good pain experience outcome. The continuous independent variables were entered into the logistic regression model using the original measurement scale or score; adjusted ORs estimate the increase in the odds of a good pain experience outcome per unit increase in the independent variable, after adjustment for all the other variables in the model. BMI ⫽ body mass index; K/L ⫽ Kellgren/Lawrence.

cantly lower odds of a good pain experience outcome and higher self-efficacy was associated with significantly higher odds of a good outcome. We used a new approach developed from previously identified pain stages (5) to assess outcome. The best way to evaluate pain experience in knee OA over the long term is unclear (1– 4); yet, it is clear that pain pattern in knee OA has its own natural history (which may not parallel that of structural disease progression). A change in pain intensity between 2 time points is difficult to interpret because of the fluctuations of knee OA pain and individual adaptation to lessen it, and the meaningfulness of small increments of change is questionable. Severely skewed distributions of continuous pain intensity change data are not uncommon, leading to data-driven ordinal conversion (2– 4). Some instruments assess multiple dimensions of pain (36) but do not directly provide interpretable stages. A relatively simple approach that provides a big picture view, the pain stage outcome captures patterns of the pain experience incorporating adaptations to lessen pain and is interpretable and meaningful to a person with knee OA. The current paradigms of pain in knee OA include biologic, environmental, psychological, and social processes (6,27,37). Cognitive and emotional processes contribute to both individual perception and impact of pain (6). Catastrophizing may act to influence outcome through many pathways by interfering with healthy behaviors, adaptive coping mechanisms, social interactions, central nervous system pain processing, and muscle function and activity (6). Catastrophizing, a negative response to pain, may be as important to outcome as the pain itself (28). Our findings suggest pain catastrophizing and self-efficacy play an important role in 2-year outcome. Pain catastrophizing has been associated with pain intensity in previous knee OA studies (7–11). Pain catastrophizing explained a significant proportion of variance in pain measures in overweight and obese patients with knee OA (7). In the only previous observational longitudinal study (i.e., not dealing with total knee replacement) we were able to identify (11), higher pain catastrophizing was associated with worse pain outcome (defined as ⱖ50% worsening between baseline and 1-year followup using a 0 –10 numerical rating scale for the past 7-day knee pain intensity) (11). A relationship between self-efficacy and pain in knee OA has been previously reported in cross-sectional studies (13– 15). Self-efficacy and other factors explained racial differences in pain (13). Patients reporting higher self-efficacy rated pain stimuli as less unpleasant and had a greater tolerance (15). Catastrophizing and self-efficacy are process components that may fall within an overarching sense of helplessness or optimism (27,38,39); it has been theorized that, while they may be related, catastrophizing and self-efficacy work independently (38). In keeping with this, in our study, each was significantly associated with outcome in models adjusting for the other. We did not find an association between depressive symptoms or depression and outcome, perhaps due to their infrequency in our sample. An association has been found in several cross-sectional studies (16 –21). In a longitudinal study, Hawker et al (24) found that current OA pain predicted future fatigue and physical function, fa-

Pain Experience Outcome in Knee OA tigue and function in turn predicted future depressed mood, depressed mood and fatigue exacerbated each other, and fatigue and poor function but not depressed mood led to worsening of OA pain. Riddle et al found that depressive symptoms were associated with 2-year change in WOMAC pain, noting that the magnitude of worsening predicted for each year was small (22). In a study of 3 general practices in North Staffordshire UK, depression was associated with the onset of knee pain but not progression from nonsevere to severe knee pain over 3 years (23). This study has limitations. While our study is longitudinal in a field with few longitudinal studies, its 2-year duration is relatively short, given the typical course of knee OA. However, our findings reveal that, even at the 2-year followup, change in this measure can be detected and factors associated with this outcome can be identified. Other factors may come into play, including the disease itself, when this outcome is evaluated over a longer period. Because we have only assessed pain experience at 2 time points, we cannot know whether it fluctuated between these points. The stage-based measure is more (than current approaches) a state, requiring the individual to reflect on overall status over a relatively long period of time, namely, encompassing fluctuations that occurred during that period. Nevertheless, we cannot determine the extent of fluctuation from this study. It seems likely that physical activity plays an important role; it may be easier to detect this with an objective measure. The role of activity is complex and warrants evaluation. In some individuals or at some times in an individual, different scenarios may occur; fear may lead to activity avoidance, deconditioning, and greater pain with activity and worse pain outcomes and activity may help to maintain muscle and soft tissue structure and function, contribute to health and wellbeing, and lead to improved pain outcomes. We evaluated factors individually to identify targets; however, a profile approach may help to identify groups in which to focus intervention. Cruz-Almeida et al (40) recently identified profiles in persons with knee OA; cluster 1 had high optimism with low negative affect, pain vigilance, anger, and depression; the lowest self-reported pain/disability; and the lowest sensitivity to mechanical, pressure, and thermal pain, while cluster 4 had the highest pain vigilance, reactivity, negative affect, anger, and depression; the highest self-reported pain/disability, including widespread pain; the greatest sensitivity to stimuli; and significant central sensitization to certain stimuli. To our knowledge, this study is the first to use pain experience stages as an outcome. The stages we used comprehensively encapsulate aspects of pain not well represented in usual methods. Common pain severity measures yield incomplete information concerning pain that is rated as none or mild simply because an individual modified her/his activity. Cognizant of the quality of the process Hawker et al undertook to formulate the stages, we adhered to the authors’ wording that explicitly incorporated the possibility of adaptation (e.g., predictability, triggers, and activities affected and/or avoided) and was less likely to yield an incomplete picture. While offering this advantage, it must also be allowed that stage approaches still

1833 may oversimplify reality. Individuals may, for example, experience more constant pain but cope in a manner that allows them to maintain activities. Conversely, some individuals may have predictable pain but have reduced activity because of poor coping. Our findings provide evidence that this outcome is a potentially valuable instrument to study the experience of pain over time in knee OA; hopefully, the value of this approach will stimulate development of additional tools that are meaningful to persons with knee OA. For clinical practice, our findings illustrate an aspect of progression of which both providers and patients should be aware. Pain catastrophizing and self-efficacy are important targets to help to prevent the pain pattern from progressing in a distressing way, which may in turn contribute to subsequent poor outcomes. Given its influence on many facets of the pain experience, catastrophizing is an appealing target for interventions to move individuals from a high risk to a lower risk group (6). Our findings further support the need for a multifaceted approach to OA pain management directed at pain coping and self-efficacy. Such interventions may require more than self-management education programs, which were reported to result in no or small benefits in OA in a systematic review (41), potentially incorporating pain coping skills training and interventions that include a partner (27). In recent trials of knee OA patients with elevated catastrophizing scheduled for total knee replacement, those receiving pain coping skills training had greater reductions in pain severity and catastrophizing (42), and overweight and obese patients with knee OA randomized to pain coping skills training and lifestyle behavioral weight management had better WOMAC pain outcome and improved self-efficacy versus either intervention alone or versus standard care control (43). In conclusion, in persons with knee OA, higher pain catastrophizing was associated with significantly lower odds of a good pain experience outcome, and higher selfefficacy was associated with significantly higher odds of a good outcome at the 2-year followup. Specifically targeting these factors in management may improve pain outcome in knee OA. This pain experience outcome may provide a meaningful and interpretable means to assess the evolution of pain in knee OA. AUTHOR CONTRIBUTIONS All authors were involved in drafting the article or revising it critically for important intellectual content, and all authors approved the final version to be submitted for publication. Dr. Sharma had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Study conception and design. Chmiel, Hayes, Sharma. Acquisition of data. Rayahin, Belisle, Zhang, Sharma. Analysis and interpretation of data. Rayahin, Chmiel, Almagor, Chang, Moisio, Sharma.

REFERENCES 1. Hawker GA. Experiencing painful osteoarthritis: what have we learned from listening? Curr Opin Rheumatol 2009;21: 507–12. 2. Hutchings A, Calloway M, Choy E, Hooper M, Hunter DJ,

1834

3. 4.

5.

6. 7.

8. 9.

10. 11.

12.

13.

14.

15.

16.

17.

18.

19. 20.

Jordan JM, et al. The Longitudinal Examination of Arthritis Pain (LEAP) study: relationships between weekly fluctuations in patient-rated joint pain and other health outcomes. J Rheumatol 2007;34:2291–300. Allen KD, Coffman CJ, Golightly YM, Stechuchak KM, Keefe FJ. Daily pain variations among patients with hand, hip, and knee osteoarthritis. Osteoarthritis Cartilage 2009;17:1275– 82. Zhang Y, Zhang B, Wise B, Niu J, Zhu Y. Statistical approaches to evaluating the effect of risk factors on the pain of knee osteoarthritis in longitudinal studies. Curr Opin Rheumatol 2009;21:513–9. Hawker GA, Stewart L, French MR, Cibere J, Jordan JM, March L, et al. Understanding the pain experience in hip and knee osteoarthritis: an OARSI/OMERACT initiative. Osteoarthritis Cartilage 2008;16:415–22. Edwards RR, Cahalan C, Mensing G, Smith M, Haythornthwaite JA. Pain, catastrophizing, and depression in the rheumatic diseases. Nat Rev Rheumatol 2011;7:216 –24. Somers TJ, Keefe FJ, Pells JJ, Dixon KE, Waters SJ, Riordan PA, et al. Pain catastrophizing and pain-related fear in osteoarthritis patients: relationships to pain and disability. J Pain Symptom Manage 2009;37:863–72. Keefe FJ, Caldwell DS, Queen K, Gil KM, Martinez S, Crisson JE, et al. Osteoarthritic knee pain: a behavioral analysis. Pain 1987;28:309 –21. Perrot S, Poiraudeau S, Kabir M, Bertin P, Sichere P, Serrie A, et al. Active or passive pain coping strategies in hip and knee osteoarthritis? Results of a national survey of 4,719 patients in a primary care setting. Arthritis Rheum 2008;59:1555– 62. Riddle DL, Jensen MP. Construct and criterion-based validity of brief pain coping scales in persons with chronic knee osteoarthritis pain. Pain Med 2013;14:265–75. Alschuler KN, Molton IR, Jensen MP, Riddle DL. Prognostic value of coping strategies in a community-based sample of persons with chronic symptomatic knee osteoarthritis. Pain 2013;154:2775– 81. Bandura A. Self-efficacy mechanism in physiological activation and health-promoting behavior. In: Madden J, editor. Neurobiology of learning, emotion, and affect. New York: Raven Press; 1991. p. 229. Allen KD, Oddone EZ, Coffman CJ, Keefe FJ, Lindquist JH, Bosworth HB. Racial differences in osteoarthritis pain and function: potential explanatory factors. Osteoarthritis Cartilage 2010;18:160 –7. Pells JJ, Shelby RA, Keefe FJ, Dixon KE, Blumenthal JA, Lacaille L, et al. Arthritis self-efficacy and self-efficacy for resisting eating: relationships to pain, disability, and eating behavior in overweight and obese individuals with osteoarthritic knee pain. Pain 2008;136:340 –7. Keefe FJ, Lefebvre JC, Maixner W, Salley AN Jr, Caldwell DS. Self-efficacy for arthritis pain: relationship to perception of thermal laboratory pain stimuli. Arthritis Care Res 1997;10: 177– 84. Summers MN, Haley WE, Reveille JD, Alarcon GS. Radiographic assessment and psychologic variables as predictors of pain and functional impairment in osteoarthritis of the knee or hip. Arthritis Rheum 1988;31:204 –9. Salaffi F, Cavalieri F, Nolli M, Ferraccioli G. Analysis of disability in knee osteoarthritis: relationship with age and psychological variables but not with radiographic score. J Rheumatol 1991;18:1581– 6. Brandt KD, Heilman DK, Slemenda C, Katz BP, Mazzuca S, Braunstein EM, et al. A comparison of lower extremity muscle strength, obesity, and depression scores in elderly subjects with knee pain with and without radiographic evidence of knee osteoarthritis. J Rheumatol 2000;27:1937– 46. Zautra AJ, Smith BW. Depression and reactivity to stress in older women with rheumatoid arthritis and osteoarthritis. Psychosom Med 2001;63:687–96. Wolfe F. Determinants of WOMAC function, pain and stiffness scores: evidence for the role of low back pain, symptom counts, fatigue and depression in osteoarthritis, rheumatoid arthritis and fibromyalgia. Rheumatology (Oxford) 1999;38: 355– 61.

Rayahin et al 21. Sale JE, Gignac M, Hawker G. The relationship between disease symptoms, life events, coping and treatment, and depression among older adults with osteoarthritis. J Rheumatol 2008;35:335– 42. 22. Riddle DL, Kong X, Fitzgerald GK. Psychological health impact on 2-year changes in pain and function in persons with knee pain: data from the Osteoarthritis Initiative. Osteoarthritis Cartilage 2011;19:1095–101. 23. Jinks C, Jordan KP, Blagojevic M, Croft P. Predictors of onset and progression of knee pain in adults living in the community: a prospective study. Rheumatology (Oxford) 2008;47:368 –74. 24. Hawker GA, Gignac MA, Badley E, Davis AM, French MR, Li Y, et al. A longitudinal study to explain the pain-depression link in older adults with osteoarthritis. Arthritis Care Res (Hoboken) 2011;63:1382–90. 25. Ferreira VM, Sherman AM. The relationship of optimism, pain and social support to well-being in older adults with osteoarthritis. Aging Ment Health 2007;11:89 –98. 26. Blixen CE, Kippes C. Depression, social support, and quality of life in older adults with osteoarthritis. Image J Nurs Sch 1999;31:221– 6. 27. Keefe FJ, Somers TJ. Psychological approaches to understanding and treating arthritis pain. Nat Rev Rheumatol 2010;6: 210 – 6. 28. Sullivan MJ, Thorn B, Haythornthwaite JA, Keefe F, Martin M, Bradley LA, et al. Theoretical perspectives on the relation between catastrophizing and pain. Clin J Pain 2001;17:52– 64. 29. Sullivan MJ, Bishop S, Pivik J. The Pain Catastrophizing Scale: development and validation. Psychol Assess 1995;7: 524 –32. 30. Lorig K, Chastain RL, Ung E, Shoor S, Holman HR. Development and evaluation of a scale to measure perceived selfefficacy in people with arthritis. Arthritis Rheum 1989;32:37– 44. 31. Smarr KL, Keefer AL. Measures of depression and depressive symptoms: Beck Depression Inventory-II (BDI-II), Center for Epidemiologic Studies Depression Scale (CES-D), Geriatric Depression Scale (GDS), Hospital Anxiety and Depression Scale (HADS), and Patient Health Questionnaire-9 (PHQ-9). Arthritis Care Res (Hoboken) 2011;63 Suppl 11:S454 – 66. 32. Sherbourne CD, Stewart AL. The MOS social support survey. Soc Sci Med 1991;32:705–14. 33. Buckland-Wright C. Protocols for precise radio-anatomical positioning of the tibiofemoral and patellofemoral compartments of the knee. Osteoarthritis Cartilage 1995;3 Suppl A:71– 80. 34. Katz JN, Chang LC, Sangha O, Fossel AH, Bates DW. Can comorbidity be measured by questionnaire rather than medical record review? Med Care 1996;34:73– 84. 35. Washburn RA, Smith KW, Jette AM, Janney CA. The Physical Activity Scale for the Elderly (PASE): development and evaluation. J Clin Epidemiol 1993;46:153– 62. 36. Hawker GA, Mian S, Kendzerska T, French M. Measures of adult pain: Visual Analog Scale for Pain (VAS Pain), Numeric Rating Scale for Pain (NRS Pain), McGill Pain Questionnaire (MPQ), Short-Form McGill Pain Questionnaire (SF-MPQ), Chronic Pain Grade Scale (CPGS), Short Form-36 Bodily Pain Scale (SF-36 BPS), and Measure of Intermittent and Constant Osteoarthritis Pain (ICOAP). Arthritis Care Res (Hoboken) 2011;63 Suppl 11:S240 –52. 37. Neogi T. The epidemiology and impact of pain in osteoarthritis. Osteoarthritis Cartilage 2013;21:1145–53. 38. McKnight PE, Afram A, Kashdan TB, Kasle S, Zautra AJ. Coping self-efficacy as a mediator between catastrophizing and physical functioning: treatment target selection in an osteoarthritis sample. J Behav Med 2010;33:239 – 49. 39. Brenes GA, Rapp SR, Rejeski WJ, Miller ME. Do optimism and pessimism predict physical functioning? J Behav Med 2002; 25:219 –31. 40. Cruz-Almeida Y, King CD, Goodin BR, Sibille KT, Glover TL, Riley JL, et al. Psychological profiles and pain characteristics of older adults with knee osteoarthritis. Arthritis Care Res (Hoboken) 2013;65:1789 –94.

Pain Experience Outcome in Knee OA 41. Kroon FP, van der Burg LR, Buchbinder R, Osborne RH, Johnston RV, Pitt V. Self-management education programmes for osteoarthritis. Cochrane Database Syst Rev 2014;1: CD008963. 42. Riddle DL, Keefe FJ, Nay WT, McKee D, Attarian DE, Jensen MP. Pain coping skills training for patients with elevated pain catastrophizing who are scheduled for knee arthroplasty: a

1835 quasi-experimental study. Arch Phys Med Rehabil 2011;92: 859 – 65. 43. Somers TJ, Blumenthal JA, Guilak F, Kraus VB, Schmitt DO, Babyak MA, et al. Pain coping skills training and lifestyle behavioral weight management in patients with knee osteoarthritis: a randomized controlled study. Pain 2012;153: 1199 –209.