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

Authors


Abstract

Objective

To study pain coping strategies in patients with hip and knee osteoarthritis (OA), and to assess the psychometric qualities of the French version of the Pain Coping Inventory (PCI).

Methods

We conducted a national, cross-sectional survey in a primary care setting in France. A total of 1,811 general practitioners included 5,324 patients with hip and knee OA who completed several questionnaires, including the PCI, which assesses ability to cope with pain.

Results

The records of 4,719 (86.4%) patients were analyzed (knee 2,781; hip 1,553; hip and knee 385). Supporting the structure of the original questionnaire, we found that the 33 PCI questionnaire items could be grouped into 3 domains defining active coping strategies and 3 defining passive coping strategies. Acceptable convergent validity was found for the PCI (Cronbach's alpha coefficient for each domain >0.68). Coping strategy scores were significantly higher in patients with both knee and hip involvement (mean ± SD 2.3 ± 0.4) than for patients with OA at 1 site (mean ± SD 2.1 ± 0.4), and in women compared with men (P < 0.001). The use of passive pain coping strategies increased with OA duration, and was greater in older and overweight patients, in patients with no current physical activity or major impairment, in retired and nonworking patients, and in patients who were not married, and to a lesser extent in patients with higher pain intensity. Compared with previous data, patients with OA demonstrated lower active and higher passive strategies than patients with rheumatoid arthritis and other chronic painful conditions.

Conclusion

The PCI has good structural validity and is highly suitable for analyzing active and passive pain coping strategies in OA. In OA, active and passive coping strategies differ significantly as a function of age, body mass index, OA involvement, professional and marital status, sport activities, and OA duration, with pain intensity having a weaker effect.

INTRODUCTION

Osteoarthritis (OA) generally causes significant chronic pain and disability, especially in the lower extermities. Cognitive and behavioral reactions to chronic pain may affect pain, functional capacity, and psychological functioning in patients with OA (1). These reactions to pain are commonly referred to as pain coping strategies and may be classified as general, passive, and active strategies. OA interferes with many domains, therefore, approaches to OA treatment are mostly multimodal, with increasing focus on pain coping strategies adapted to individual patients (2). Analyses of pain coping strategies in patients with OA are important for minimizing the impact of symptoms and establishing appropriate disease management, taking into account several factors, including age, sex, body mass index (BMI), and type of handicap (3).

Pain coping strategies have been extensively studied in many rheumatologic conditions, including rheumatoid arthritis (Vanderbilt Pain Management Inventory; VPMI [4]), low back pain (Pain Cognition List; PCL [5]), and fibromyalgia (6). Numerous studies have also dealt with pain coping strategies in patients with OA (2, 3, 7–9). Several pain coping scales are available for the assessment of chronic pain (Coping Strategies Questionnaire; CSQ [10], PCL [5], VPMI [4], Chronic Pain Coping Inventory [11], Vanderbilt Multidimensional Pain Coping Inventory [12]) and were developed for patients with specific subtypes of chronic pain. The Pain Coping Inventory (PCI), designed by Kraaimaat and Evers (13), has been validated in painful chronic conditions such as rheumatoid arthritis, cephalgia, and painful conditions of multiple origins. The PCI has not yet been validated for patients with OA of the hip or knee, but various aspects of the PCI have been shown to be valid in patients with OA of the hip or knee (14, 15). This scale has also been used to study the relationship between pain coping strategies and pain in OA (15–17).

We chose to use this questionnaire because it is easy to administer and analyze. The PCI contains 33 questions, which can be pooled into 6 domains of cognitive and behavioral strategies for dealing with chronic pain: pain transformation, distraction, reducing demands, retreating, worrying, and resting. These domains can be grouped into active (transformation, distraction, reducing demands) and passive (retreating, worrying, resting) pain coping dimensions. The relationship between coping with chronic pain and physical and psychological adjustment has been studied in detail (18), but little is known about the relationship between pain coping strategies and pain in OA.

We explored pain coping strategies and studied the psychometric qualities of the French version of the PCI in patients with hip and knee OA.

PATIENTS AND METHODS

Three thousand general practitioners (GPs) were selected to participate in this national, multicenter, observational study, resulting in a total of 2,000 selecting centers and 5,000 enrolled patients. These GPs were selected from a database listing all French GPs. Each GP was asked to include the first 3 patients age 50 years or older with hip or knee OA according to American College of Rheumatology criteria (19) seen by the GP from March to June 2004. Patients presenting with any of the following criteria were not enrolled: pain originating from another painful condition, neurologic disease affecting the lower extremities, other severe conditions with a potentially significant impact on daily life activities, and previous lower extremity amputations. The following demographic and clinical data were recorded: age, sex, weight, height, BMI, site of OA (knee, hip, both), and marital and professional status.

All patients were asked to complete several questionnaires. Pain coping strategies were assessed with the French version of the PCI. Pain intensity (average pain at rest and on movement during the last 24 hours, average pain for the last 8 days) was evaluated via an 11-point numerical pain scale. The French version (20) of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) physical function subscale (21), which assesses knee-related physical function over the last 48 hours, was used to assess physical function.

The project was approved by the Paris-Cochin Research Ethics Committee. Data were analyzed using SAS, version 8.2 software (SAS Institute, Cary, NC).

We analyzed pain coping strategies in patients with lower extremity OA, as assessed by the PCI. This approach made it possible to analyze the 6 pain coping dimensions defined by the PCI and to examine the types of pain coping strategies used (active and passive) and the effect of pain on those strategies. The first 3 domains of the PCI define active coping strategies (mean of 3 scores), whereas the last 3 domains define passive strategies (mean of 3 scores). We assessed the correlation between pain coping strategies and demographic and clinical variables using Spearman's rank correlation analyses. For each domain, analysis of covariance (ANCOVA) was performed, comparing the 2 sites of OA and adjusting for sex, BMI (continuous), age (continuous), duration (continuous), marital status (categorical, with 3 classifications: part of a couple, widowed, or separated/divorced), professional status (categorical, with 8 validated French social classifications), and sports activities (categorical, with 3 classifications: no activity, occasional, and regular activity).

We also assessed the structure of the PCI. We carried out principal components analysis (PCA) on the psychometric properties of the PCI to check their unidimensionality, the quality of separation of each item, and the linearity of each domain. PCA is a data set simplification technique in which the number of dimensions of a multidimensional data set is reduced for analysis. It was used to extract factors from the subscale scores of the PCI. Spearman's correlation coefficients were considered to be excellent (>0.91), good (0.90–0.71), moderate (0.70–0.51), fair (0.50–0.31), or poor (<0.31) (18). Independent factors were obtained with the varimax rotation method. Internal consistency was assessed by calculating Cronbach's alpha coefficient for each PCI domain.

RESULTS

Characteristics of the patients.

Of the physicians contacted, 2,419 were enrolled in the study and 1,881 were active, contributing at least 1 patient to the study. This resulted in a participation rate of 75%. No significant demographic differences were identified between participating and nonparticipating physicians. The 1,811 active physicians included 5,324 patients, corresponding to a mean ± SD of 2.9 ± 0.2 patients per physician.

We analyzed data for 4,719 of the 5,324 patients included, which corresponded to 89% of the selected population (Table 1). We analyzed all patients for whom no major violation of the protocol was observed. The major violations observed in the excluded patients were age <50 years (321 patients excluded), no information about the site of OA (23 excluded), and hip or knee prosthesis (7 excluded).

Table 1. Demographic and clinical characteristics of patients with hip or knee OA*
 Knee OAHip OAHip and knee OAWhole sample
  • *

    Values are the number (percentage) unless otherwise indicated. OA = osteoarthritis; BMI = body mass index; WOMAC = Western Ontario and McMaster Universities Osteoarthritis Index.

Patients2,781 (58.9)1,553 (32.9)385 (8.2)4,719 (100)
Age, mean ± SD years66.7 ± 9.167.4 ± 8.770.2 ± 9.267.2 ± 9.0
Male1,126 (40.5)720 (46.5)133 (34.7)1,979 (42.0)
Weight, mean ± SD kg76.9 ± 13.174.6 ± 12.777.0 ± 13.776.1 ± 13.1
Height, mean ± SD cm166.6 ± 8.2167.2 ± 8.1165.5 ± 8.6166.7 ± 8.2
BMI, mean ± SD kg/m227.7 ± 4.426.6 ± 3.928.1 ± 4.627.4 ± 4.3
OA duration, mean ± SD years5.9 ± 5.05.4 ± 4.85.9 ± 5.05.7 ± 4.9
Pain, mean ± SD    
 Pain at rest4.1 ± 2.24.1 ± 2.24.6 ± 2.14.1 ± 2.2
 Pain on movement5.9 ± 1.85.9 ± 1.86.3 ± 1.85.9 ± 1.8
 Pain over the last 8 days5.0 ± 1.75.1 ± 1.75.5 ± 1.65.1 ± 1.7
Marital status    
 Couple1,902 (68.7)1,082 (70.1)236 (61.5)3,220 (68.6)
 Divorced161 (5.8)92 (6.0)21 (5.5)274 (5.8)
 Widowed660 (23.8)347 (22.5)120 (31.3)1,127 (24.0)
 Single47 (1.7)22 (1.4)7 (1.8)76 (1.6)
Professional status    
 Higher education333 (12.1)202 (13.2)43 (11.3)578 (12.4)
 Craftsman95 (3.4)60 (3.9)7 (1.8)162 (3.5)
 Workman219 (7.9)102 (6.6)26 (6.8)347 (7.4)
 Employee262 (9.5)143 (9.3)28 (7.3)433 (9.2)
 Farmer100 (3.6)65 (4.2)16 (4.2)181 (3.9)
 Shopkeeper108 (3.9)60 (3.9)8 (2.1)176 (3.8)
 Company director32 (1.2)15 (1.0)4 (1.0)51 (1.1)
 Executive83 (3.0)55 (3.6)13 (3.4)151 (3.2)
 Senior executive59 (2.1)37 (2.4)5 (1.3)101 (2.2)
 Self-employed87 (3.1)43 (2.8)8 (2.1)138 (2.9)
 Intermediate professions34 (1.2)17 (1.1)6 (1.6)57 (1.2)
 Retired1,303 (47.1)746 (48.5)206 (53.6)2,255 (48.1)
 Unemployed (seeking work)16 (0.6)5 (0.3)1 (0.3)22 (0.5)
 Without profession369 (13.3)189 (12.3)56 (14.6)614 (13.1)
Physical activity    
 None1,859 (74.9)1,002 (72.1)279 (80.9)3,140 (74.5)
 Occasional467 (18.8)313 (22.5)48 (13.9)828 (19.6)
 Current155 (6.2)75 (5.4)18 (5.2)248 (5.9)
Impairment, mean ± SD    
 No. of days per month disturbed by OA18.1 ± 9.218.5 ± 9.418.7 ± 9.518.2 ± 9.3
 WOMAC function46.6 ± 18.150.6 ± 16.956.4 ± 17.248.7 ± 17.9

The 4,719 patients included had a mean ± SD age of 67 ± 9 years, and 58% were women (Table 1). Mean ± SD BMI was 27.4 ± 4 kg/m2. Most patients were living with a partner (69%), had been educated at the primary (47%) or secondary (35%) school level, and approximately half were retired. No sports activities were reported for 75% of the patients. OA most frequently affected only the knee (n = 2,781 [59%]) or hip (n = 1,553 [33%]), with both joints affected in only a small number of patients (n = 385). The mean ± SD duration of OA since diagnosis was 5.7 ± 4.9 years at the time of the study. On average, OA had a significant impact on daily life on 18.2 ± 9.3 days per month. Mean ± SD pain intensity was 4.1 ± 2.2 at rest, 5.9 ± 1.8 on movement, and 5.1 ± 1.7 over an 8-day period. For each of these 3 pain measurements, the values obtained were similar in patients with knee and hip OA, but were significantly higher (P > 0.01) in patients in whom both joints were affected (4.6 ± 2.1, 6.3 ± 1.8, and 5.5 ± 1.6, respectively).

Structure of the PCI.

We carried out PCA on the data set for the 33 PCI items. We identified 6 factors: a first factor (items 9, 10, 11, 12, 13, 14, and 32) similar to the retreating domain of the PCI (6 of 7 items), a second factor (items 17, 24, 25, 26, 27, 28, 29, and 31) similar to the worrying domain of the PCI (8 of 9 items), a third factor (items 1, 5, 6, 7, 8, and 33) similar to the resting domain (5 of 5 items), a fourth domain (items 19, 20, 21, and 22) similar to the distraction domain (4 of 5 items), a fifth factor (items 15, 16, 18, and 30) identical to the pain transformation domain, and a sixth factor (items 2, 3, and 4) identical to the reducing demands domain of the PCI (Table 2). Cronbach's alpha statistics were calculated for each PCI domain and all alpha coefficients were well within the acceptable range (between 0.68 and 0.74). These analyses indicate that the structure of the PCI is valid for patients with OA of the hip and/or knee.

Table 2. Pain Coping Inventory (PCI) scores and principal components analysis of PCI (33 items) in 4,598 patients
PCI itemMean ± SD score (range 0–4)Rotated factor pattern
Factor 1Factor 2Factor 3Factor 4Factor 5Factor 6
  • *

    Values >0.4.

PCI 1: I stop my activities2.3 ± 0.80.140.310.62*−0.11−0.030.03
PCI 2: I continue my activities, but with less effort2.5 ± 0.7−0.010.090.080.090.070.83*
PCI 3: I continue my activities, but at a slower pace2.5 ± 0.70.010.110.150.050.090.86*
PCI 4: I continue my activities, but with less precision2.2 ± 0.90.230.160.27−0.050.090.65*
PCI 5: I confine myself to simple activities2.5 ± 0.90.150.220.70*−0.020.050.25
PCI 6: I take care that I don't have to exert myself physically2.6 ± 0.90.080.240.75*−0.01−0.010.14
PCI 7: I take rest by sitting or lying down2.5 ± 0.90.200.170.74*0.12−0.040.09
PCI 8: I take on a comfortable body posture2.6 ± 0.80.170.110.68*0.270.010.08
PCI 9: I take a bath or shower1.8 ± 0.80.53*0.010.050.310.130.08
PCI 10: I take care that I don't get upset1.7 ± 0.80.76*0.150.150.090.070.04
PCI 11: I retreat into a restful environment1.8 ± 0.80.75*0.120.300.130.050.01
PCI 12: I take care that I am not bothered by annoying sounds1.6 ± 0.80.82*0.130.200.090.070.01
PCI 13: I take care that I am not bothered by the light1.4 ± 0.70.80*0.110.090.090.130.05
PCI 14: I take care of what I eat or drink1.9 ± 0.90.47*0.110.060.210.190.05
PCI 15: I pretend the pain is not present2.1 ± 0.80.05−0.04−0.050.080.85*0.08
PCI 16: I pretend the pain does not concern my body1.8 ± 0.80.190.00−0.050.080.84*0.09
PCI 17: I focus on the pain all the time1.7 ± 0.80.49*0.43*0.16−0.060.120.02
PCI 18: I imagine the pain to be less violent than it really is1.9 ± 0.80.230.150.060.260.63*0.05
PCI 19: I think of pleasant things or events2.0 ± 0.80.280.100.090.53*0.43*0.03
PCI 20: I distract myself by undertaking a physical activity1.6 ± 0.80.32−0.04−0.300.43*0.270.07
PCI 21: I distract myself by reading, listening to music, watching a TV program or similar2.2 ± 0.90.150.000.110.81*0.050.01
PCI 22: I do something I find pleasant2.2 ± 0.80.110.030.040.84*0.150.03
PCI 23: I self-administer other physical stimuli1.6 ± 0.80.44*0.23−0.080.250.220.10
PCI 24: I think of all the things that I haven't been able to do because I am in pain2.0 ± 0.90.210.59*0.130.150.070.09
PCI 25: I start worrying2.4 ± 0.90.080.80*0.240.02−0.030.09
PCI 26: I wonder about the cause of the pain2.3 ± 0.90.100.81*0.190.02−0.030.08
PCI 27: I think that the pain will worsen2.7 ± 0.9−0.070.76*0.200.03−0.020.07
PCI 28: I think of moments when I was not in pain1.9 ± 0.80.330.42*0.040.220.180.12
PCI 29: I think I will go mad with pain1.5 ± 0.80.48*0.55*0.14−0.100.090.04
PCI 30: I remember other people's difficulties1.9 ± 0.80.290.290.050.260.310.05
PCI 31: I think that others do not understand what it means to be in such pain2.1 ± 0.90.250.60*0.18−0.020.110.06
PCI 32: I separate myself from others1.7 ± 0.80.53*0.44*0.24−0.040.010.02
PCI 33: When I am outdoors I try to return home as soon as possible2.1 ± 0.80.240.44*0.47*−0.010.000.05

Pain coping strategies in patients with hip and knee OA.

Pain coping strategies were assessed with the PCI. We analyzed all 33 items and 6 domains of the PCI, with scores ranging from 1 (almost never) to 4 (very often) (Table 2).

The scores obtained for the 6 PCI domains ranged from 1.7 to 2.4, close to the previous norm obtained by Kraaimaat and Evers (13) (Table 3). For active pain coping strategies, the mean ± SD scores of the 4,719 OA patients were 1.9 ± 0.6 for pain transformation, 1.9 ± 0.6 for distraction, and 2.4 ± 0.6 for reducing demands. The scores for passive pain coping were 1.7 ± 0.6 for retreating, 2.0 ± 0.6 for worrying, and 2.5 ± 0.7 for resting. The highest scores were obtained for the reducing demands and resting domains. These 2 domains corresponded to those in which patients developed the most highly adapted strategies for coping with pain (i.e., maintenance of current activity while limiting pain intensity). There were no significant differences between groups of active and passive strategies (mean ± SD scores of 2.1 ± 0.4 and 2.1 ± 0.5, respectively) for the whole population: passive and active strategies were used with equal frequency.

Table 3. Differences between mean ± SD pain coping scores assessed by the PCI subscales in patients with hip OA, patients with knee OA, and patients with OA at both sites*
 OA coping scores from current studyReference values from ref.13
PKnee OA (n = 2,781)Hip OA (n = 1,553)Knee and hip OA (n = 385)Total (n = 4,719)PRheumatoid arthritis (n = 627)Chronic pain (n = 104)
  • *

    Values are the mean ± SD unless otherwise indicated. PCI = Pain Coping Inventory; OA = osteoarthritis; NS = not significant.

  • Scores of patients from the reference study published by Kraaimaat and Evers (13) are indicated for indirect comparison.

Active PCI subscaleNS2.1 ± 0.42.1 ± 0.42.2 ± 0.52.1 ± 0.4< 0.052.22.0
 Factor 1: pain transformationNS1.9 ± 0.61.9 ± 0.61.9 ± 0.61.9 ± 0.6< 0.012.3 ± 0.72.1 ± 0.6
 Factor 2: distractionNS1.9 ± 0.62.0 ± 0.62.0 ± 0.61.9 ± 0.6< 0.012.3 ± 0.62.2 ± 0.6
 Factor 3: reducing demands< 0.052.4 ± 0.62.4 ± 0.62.6 ± 0.62.4 ± 0.6< 0.012.1 ± 0.71.8 ± 0.6
Passive PCI subscale< 0.012.1 ± 0.52.1 ± 0.52.3 ± 0.62.1 ± 0.5< 0.051.91.8
 Factor 4: retreatingNS1.7 ± 0.61.7 ± 0.61.9 ± 0.61.7 ± 0.6NS1.7 ± 0.51.6 ± 0.6
 Factor 5: worryingNS2.0 ± 0.62.0 ± 0.62.2 ± 0.62.0 ± 0.6< 0.011.8 ± 0.51.6 ± 0.6
 Factor 6: resting< 0.0012.5 ± 0.62.5 ± 0.62.8 ± 0.62.5 ± 0.7NS2.4 ± 0.62.4 ± 0.6

ANCOVA for PCI domains and site of OA demonstrated a significant difference according to site of OA for 3 scores: 2 pain coping domains (reducing demands [P = 0.0369] and resting [P = 0.0042]) and total passive coping strategies (P = 0.0106) (Table 3). All 3 of these scores were significantly higher in patients with OA of both the knee and the hip than in patients with OA at only 1 site. The total passive pain coping score was significantly higher in patients with knee OA than in patients with hip OA following adjustment for sex, BMI, and OA duration. ANCOVA for PCI domains and demographic characteristics revealed significant differences between the sexes: women had significantly higher scores in 5 of the 6 domains (pain transformation [P = 0.017], reducing demands [P < 0.0001], retreating [P < 0.0001], worrying [P < 0.0001], and resting [P < 0.0001]), and for both active (P = 0.003) and passive (P < 0.0001) strategies (Table 4). Therefore, women made more extensive use of pain coping strategies, both active and passive, than men when faced with pain. The scores for the 3 domains of passive coping increased significantly with OA duration. In conclusion, the use of passive pain coping strategies increased significantly with age, BMI, and OA duration and differed between the sexes (greater use of such strategies in women).

Table 4. Demographic and clinical factors affecting the 6 Pain Coping Inventory dimensions (analysis of covariance)*
DimensionPrF
  • *

    Each domain was tested by analysis of covariance (adjustment for age, body mass index [BMI], duration) or analysis of variance (adjustment for sex).

  • Correlation coefficient for quantitative data.

  • Correlation coefficient for qualitative data.

Pain transformation   
 Sex0.0050 5.59
 Age0.67220.00975 
 BMI0.1448−0.019 
 Duration0.2244−0.025 
 Marital status0.4896 0.81
 Professional status0.6965 0.76
 Sports activities0.0003 8.02
Distraction   
 Sex0.1215 1.94
 Age0.4407−0.00583 
 BMI< 0.0001−0.075 
 Duration0.2127−0.016 
 Marital status0.0191 3.32
 Professional status< 0.0001 7.06
 Sports activities< 0.0001 58.87
Reducing demands   
 Sex< 0.0001 28.63
 Age< 0.00010.12962 
 BMI0.3832−0.013 
 Duration< 0.00010.098 
 Marital status< 0.0001 14.92
 Professional status0.0003 3.07
 Sports activities0.0001 9.21
   
 Sex< 0.0001 49.17
 Age< 0.00010.14001 
 BMI0.03320.046 
 Duration< 0.00010.107 
 Marital status< 0.0001 23.15
 Professional status< 0.0001 3.32
 Sports activities< 0.0001 12.05
Worrying   
 Sex< 0.0001 42.44
 Age< 0.00010.08067 
 BMI< 0.00010.086 
 Duration< 0.00010.082 
 Marital status< 0.0001 15.10
 Professional status< 0.0001 3.43
 Sports activities< 0.0001 36.32
Resting   
 Sex< 0.0001 78.30
 Age< 0.00010.29061 
 BMI< 0.00010.135 
 Duration< 0.00010.222 
 Marital status< 0.0001 51.19
 Professional status< 0.0001 18.58
 Sports activities< 0.0001 106.75
Active pain coping strategies   
 Sex0.0003 8.85
 Age0.32170.06349 
 BMI0.1707−0.035 
 Duration0.00230.051 
 Marital status0.0309 2.96
 Professional status0.2240 1.28
 Sports activities< 0.0001 10.11
Passive pain coping  strategies   
 Sex< 0.0001 81.17
 Age< 0.00010.21093 
 BMI< 0.00010.10916 
 Duration< 0.00010.16902 
 Marital status< 0.0001 40.66
 Professional status< 0.0001 9.62
 Sports activities< 0.0001 63.00

Marital status, professional status, sports activities, and OA duration may also influence pain coping strategies in patients with lower extremity OA (Table 4). Four of the 6 domains of the PCI were influenced by marital status: reducing demands scores were particularly high in widowed patients, and the scores for the 3 passive pain coping domains were significantly lower in married patients than in unmarried patients. Professional status was also an important factor, but analyses were explorative. Two of the 3 active pain coping domains were significantly affected by professional status: distraction scores were lower in workmen, craftsmen, farmers, retired patients, unemployed patients, and nonworking patients; reducing demands scores were lower in unemployed patients. The scores for the 3 passive pain coping domains also depended on professional status: retreating and resting domain scores were significantly higher in retired, unemployed, and nonworking patients; worrying scores were significantly higher in self-employed patients and managers. Thus, active pain coping strategy scores were significantly lower in unemployed patients, and passive pain coping scores were significantly higher in retired, unemployed, and nonworking patients. Sports activities were associated with differences in all 6 domains of the PCI: active pain coping scores were higher in patients currently practicing sports activities, whereas passive pain coping scores were significantly lower in these patients.

We also analyzed the correlation between functional assessment score (WOMAC), pain measurements, and each domain of the PCI (Table 5). The correlation between each of the PCI domains and the WOMAC functional subscale score was poor. A good correlation between coping strategies and functional impairment was found for only 2 domains, worrying (r = 0.527) and resting (r = 0.622), with more passive coping strategies used in patients with more severe impairment. A weaker correlation (between r = 0.2 and r = 0.4) was found between the 3 pain intensity scores (pain at rest, on movement, and during the last 8 days) and passive pain coping scores (mostly worrying and resting, less for retreating); there was no correlation between active pain coping strategies and pain intensity.

Table 5. Correlations (Spearman's rank correlation coefficient) between each of the 6 Pain Coping Inventory dimensions, WOMAC functional score (17 items), and 3 types of pain assessment (pain at rest, on movement, and mean pain over the last 8 days)*
 Active pain coping dimensionsPassive pain coping dimensions
Pain transformationDistractionReducing demandsRetreatingWorryingResting
  • *

    Passive pain coping strategies are correlated with functional impairment. Passive pain coping strategies (mostly worrying and resting, less for retreating) are also weakly correlated with osteoarthritis pain intensity, unlike active pain coping strategies. WOMAC = Western Ontario and McMaster Universities Osteoarthritis Index.

WOMAC function score      
 r0.120310.101930.343320.425400.527930.62245
 P< 0.0001< 0.0001< 0.0001< 0.0001< 0.0001< 0.0001
Pain at rest      
 r0.057900.081120.162800.249840.318260.30472
 P0.0006< 0.0001< 0.0001< 0.0001< 0.0001< 0.0001
Pain on movement      
 r0.014770.008650.225430.185410.328660.38853
 P0.37890.6065< 0.0001< 0.0001< 0.0001< 0.0001
Mean pain over the last 8 days      
 r0.038450.040340.228770.251680.386200.39816
 P0.02190.0162< 0.0001< 0.0001< 0.0001< 0.0001

DISCUSSION

We analyzed 4,719 OA patients consulting French GPs (2.9 patients per GP), uniformly distributed throughout mainland France. The demographic characteristics of the participating GPs were similar to those of French GPs in general, validating our sample. This study provides original data on pain coping strategies in patients with lower extremity OA and validates the PCI for analysis of pain coping strategies in this disease.

The pain generated by OA leads to a decrease in physical function, disability, and poor quality of life, and has a major impact on functioning (22). As in many chronic diseases, patients use several coping strategies to adapt to the intensity of pain. The OA patients studied here demonstrated lower active pain coping strategies and much higher passive pain coping scores than patients with rheumatoid arthritis and those with chronic pain (Table 3), as described in the article by Kraaimaat and Evers (13). Two active pain coping strategies (pain transformation and distraction) were more important in patients with rheumatoid arthritis versus those with OA and other pain patients. On the contrary, one active pain coping strategy (reducing demands: maintenance of usual activities with limitation of intensity) was more important in OA patients than in rheumatoid arthritis patients and other pain patients. Two passive pain coping strategies (worrying and resting: limitation of activities) were more important in OA compared with rheumatoid arthritis and other pain conditions. This finding suggests that degenerative joint disease (OA) leads to more passive pain coping strategies than do inflammatory joint diseases (rheumatoid arthritis). This is probably related to the fact that pain in OA is increased by motion, although pain in rheumatoid arthritis, which mostly occurs in the morning, is usually relieved by movement, after a period of stiffness.

The site of OA was found to have a significant effect on coping strategies: scores for the reducing demands and resting domains and the total score for passive coping strategies were significantly higher in patients with OA affecting both knees and hips than in patients in whom only one of these sites was affected. We also found that passive pain coping score was significantly higher in patients with knee OA than in patients with hip OA following adjustment for sex, BMI, and OA duration. These differences in pain coping strategies may be associated with differences in functional consequences, consistent with the results reported by Allen et al (23). Some studies have found differences in pain coping strategies between patients with hip and knee OA. Steultjens et al (15) demonstrated that the use of passive coping strategies predicted a higher level of disability in patients with knee OA and that active coping style predicted a high level of pain intensity. They also showed that resting was a prospective determinant of disability for knee OA, but not for hip OA. We showed that sports activities played a positive role in coping with pain for all PCI dimensions, with patients using active coping strategies being more likely to exercise. It remains unclear whether the more active coping strategies of patients who participate in regular sports activities are a cause or a consequence, but other studies have already suggested that there is a link between coping and physical tasks (24).

Pain coping scores for all domains and types of coping were higher in women than in men, with the exception of the distraction domain. This suggests that women use a more diverse range of strategies than men when faced with pain due to OA. This may be associated with the higher reported pain intensity scores for women than for men, but may also be due to the greater impact on function, as assessed by the WOMAC, in women than in men (mean ± SD WOMAC score 51.6 ± 17.2 versus 44.4 ± 18.1; P < 0.0001). Several other studies have already demonstrated differences in the coping strategies developed by men and women in the face of persistent pain (25–29). Women are more likely than men to use emotion-focused coping strategies when dealing with OA pain (25), and this is particularly true for pain catastrophizing (27). Our study demonstrated that women developed more pain coping strategies than men in all domains, including physical domains, and both active and passive pain coping strategies. Pain coping scores were higher in older patients (>70 years), although all of the patients selected for this study were over the age of 50 years to ensure that the OA patient sample was as uniform as possible. Pain coping scores were also higher in obese patients (BMI >40 kg/m2), who had higher pain intensity scores; these patients adopted mostly passive coping strategies.

We also found that married patients had lower passive coping scores than other patients. This is consistent with previous studies showing that spouses play a very important role in coping with OA (30), as in many other chronic conditions.

PCA was carried out for all 33 items of the PCI. We identified 6 distinct factors with compositions very similar to the 6 dimensions of the PCI. Various inventories for measuring pain coping strategies have been developed, and the PCI is an easily administered questionnaire designed to assess cognitive and behavioral pain coping strategies in patients with various types of pain. The PCI was generated from existing inventories (10, 31) and from behavioral interviews with patients referred to a pain clinic, based on 114 initial items. The selection of nonredundant items and simultaneous component analysis led to the development of a 33-item inventory with 6 factors corresponding to the 6 domains, encompassing behavioral (B) and cognitive (C) pain coping strategies: pain transformation (C), distraction (C/B), reducing demands (C/B), retreating (B), worrying (C), and resting (B). The PCI has been validated for the assessment of pain coping strategies in patients with rheumatoid arthritis, fibromyalgia, chronic headaches, and in pain clinic patients (13). PCA identified the same 6 factors, grouping the same items in OA patients. Similar to Kraaimaat and Evers (13), we found that passive strategies, such as worrying and resting, were significantly associated with severe disability. Worrying was conceptualized as the cognitive aspect of pain-related anxiety. It is closely related to the so-called catastrophizing scales in other pain coping questionnaires (CSQ, PCL) (32). Future studies should investigate whether passive pain coping strategies predict poor outcomes, as reported for these other scales. Finally, we consider the PCI scales to be sensitive enough to identify groups of patients with OA using different pain coping strategies. Generally, as suggested by Kraaimaat and Evers (13), the PCI seems to be particularly suitable for studies and comparisons of pain coping strategies in many chronic pain situations, including lower extremity OA.

This study demonstrates that pain coping strategies in OA are globally well balanced between active and passive strategies and are not related to pain intensity. Women tend to make wider use of all types of pain coping strategies. Demographic and clinical factors may influence pain coping strategies, which tend to be more passive in older patients, in patients with both hip and knee involvement, and in patients with higher BMI, longer duration of OA, or greater functional impairment. Furthermore, certain personal characteristics, such as professional status, marital status, and sports activities, may also influence pain coping strategies. Comparisons with norm groups of other chronic pain patients suggest that OA patients demonstrate more passive strategies than patients with rheumatoid arthritis. This study also demonstrates that the PCI questionnaire is a valid tool for analyzing pain coping strategies in OA patients. Its use may make it possible to improve OA management, integrating pain coping strategies specifically adapted to age, sex, BMI, site of OA, OA duration, and functional impairment.

AUTHOR CONTRIBUTIONS

Dr. Perrot 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 design. Perrot, Poiraudeau, Rannou.

Acquisition of data. Perrot.

Analysis and interpretation of data. Perrot, Poiraudeau, Rannou.

Manuscript preparation. Perrot, Poiraudeau, Bertin, Sichere, Serrie, Rannou.

Statistical analysis. Kabir.

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