2.3. Measures

Demographic data were collected with a study specific questionnaire.

Pain intensity (PI) was measured with one rating using an eleven-graded Numerical Rating Scale (NRS), where 0 implied no pain and 10 maximum pain. NRS is considered to be a valid and reliable measure for pain intensity [23].

Perceived responses from a spouse/intimate partner were measured with the support, punishing responses, solicitous responses, and distracting responses subscales from the Multidimensional Pain Inventory-Swedish version (MPI-S) [24–26]. The MPI is a 32-item inventory with in total eight subscales that describe psychosocial, cognitive, and behavioral effects of chronic pain. The subscales' total score varies between 0 and 6. The internal consistency, Cronbach's alpha, was good in the current study for the subscales: support (alpha 0.91), punishing responses (alpha 0.91), solicitous responses (alpha 0.80), and distracting responses (alpha 0.77). The construct validity of MPI-S is good [25].

Catastrophizing thoughts were measured with the catastrophizing (CAT) subscale of the coping strategies questionnaire (CSQ) [27, 28]. The rating is between 0 and 6 per item, and the maximum score is 36. Higher scores indicate a higher degree of catastrophizing thoughts. The Swedish version of the whole CSQ was administered but in this study only the CAT subscale was used. The CAT subscale has shown good reliability in patients with subacute, chronic, and recurring musculoskeletal pain [11].

Fear of movement and (re)injury, mirroring the fear-avoidance construct in musculoskeletal conditions [11, 14], was measured with the Tampa Scale of Kinesiophobia (TSK) [29]. The TSK has 17 items and is rated with a 4-grade format between 1 = “strongly disagree” and 4 = “strongly agree.” The total score range is 17 to 68 with higher scores indicating more fear [11]. The total scores from TSK were used. The Swedish version has good reliability for patients with WAD [30].

Self-efficacy in performing common everyday life activities, that is, functional self-efficacy, was measured with the Self-Efficacy Scale (SES) [11, 31–33]. Participants rated their confidence in performing 20 daily activities in spite of pain. The item rating is 0–10 in which 0 = “not at all confident” and 10 = “very confident.” A total score ranges from 0 to 200. The Swedish version has shown good reliability for patients with WAD [30].

Pain related disability was measured with the Pain Disability Index (PDI) [34–36]. The PDI has seven items, which assess the degree of disability in daily activities. The rating is between 0 and 10 (0 is no interference; 10 is total interference) for each item. A total score ranges from 0 to 70. The PDI is a highly reliable and valid measure for patients with chronic pain [34, 36] and acute WAD [33]. Internal consistency was high, Cronbach's alpha  0.86 in [33]. A Swedish version of PDI was used in the present study [11].