The present study identified and evaluated a brief fear of movement scale for use in OA. Exploratory and confirmatory factor analyses identified a Brief Fear of Movement Scale for OA that includes six items from the TSK14
that capture activity avoidance due to pain-related fear of movement. The Brief Fear of Movement Scale performed consistently across diverse groups of individuals as demonstrated by factorial invariance across gender, race, education, and OA grade. The scale also demonstrated relationships with measures of pain, physical functioning, and psychological functioning indicating that this scale has convergent validity. Taken together, these results indicate that the Brief Fear of Movement Scale provides a valid approach for assessing fear of movement in OA.
An important finding from this work is that the Brief Fear of Movement Scale showed invariance across subgroups of gender, race, education level, and OA grade. Results showed that the structure (factor variances and loadings) of the measure was consistent across the subgroups examined. While slight differences in item intercepts and uniqueness were found in several cases, the small number and magnitude of these differences suggested that this measure performs consistently across subgroups40
. These results indicate that the Brief Fear of Movement Scale developed in this work can be used in diverse groups of individuals with OA.
The Brief Fear of Movement Scale demonstrated convergent validity with measures of pain, physical functioning, and psychological functioning. The strongest relationships were found between fear of movement and measures of physical function. These findings are consistent with prior studies that have demonstrated a negative impact of fear of movement on functioning in individuals with OA5–9
. The Brief Fear of Movement Scale shared approximately 25% of its variance with measures of physical functioning. The Brief Fear of Movement Scale exhibited moderate relationships with pain and psychological functioning, which is consistent with past studies in OA6,7
. Finally, the Brief Fear of Movement Scale demonstrated weak associations with OA grade, which is consistent with other work suggesting that fear of movement is important to assess in addition to disease severity5–9
For the Brief Fear of Movement Scale, we dropped the four reverse scored TSK items, item 6, and items 13 and 17 from the Activity Avoidance factor. This study and numerous studies of the TSK7,16,17,19,25,43
have found that the four reverse scored items fail to correlate with other TSK items. Item 6 was dropped because our data suggested that this item might be inappropriate for use in individuals with OA and it failed to correlate with other TSK items. Items 13 and 17 did not load with other TSK items and performed poorly in the analyses. Mielenz et al.25
also reported problems with item 13 in a study of OA and concluded that item 13 had little in common with other TSK items. Item 17 has exhibited low factor loadings in prior studies21,24,45–47
, and was among the more poorly performing items in analysis conducted by Mielenz et al.25
We chose to drop the four harm/somatic focus TSK items from the Brief Fear of Movement Scale because these items did not load on a single factor and exhibited fairly low loadings. If future measures include these items, users should be made aware that these four items may not form a single factor. In this study, two items (3 and 5) focused on the seriousness of pain loaded together on a factor, but the two remaining items showed higher loadings on the activity avoidance factor. Additional studies are needed to determine whether these four items capture information that is indicative of fear of movement in individuals with OA. It is possible that the content of these items may be more suggestive of a tendency to catastrophize about pain24
, rather than fear of movement.
While this study included a large community based sample of individuals with OA, findings need to be viewed within the particular circumstances of this study. First, this study included a single assessment, which prohibits testing reliability of the scale over time or sensitivity to changes in disease or function over time. Second, all of the variables examined for convergent validity were assessed using self-report measures, which raises possible concerns over common method bias in the estimation of these relationships. Third, these data were collected as part of a population-based study of the onset and progression of OA. Hypotheses and analyses examining the psychometric properties and convergent validity of the Brief Fear of Movement Scale were conducted post hoc. Finally, the study sample included individuals with OA who were living in North Carolina. Additional studies are needed to determine whether these results generalize to individuals living in other geographic regions and to populations with other types of disease related pain.
Fear of movement is an important target for reducing disability in individuals with OA5–10
. Having a valid measure for assessing fear of movement in OA has important clinical implications. Once identified, pain-related fear of movement could be treated using in vivo exposure techniques. Vlaeyen et al.48–50
have developed in vivo exposure techniques that enable patients with pain to learn that they can successfully experience and habituate to movements or activities that they might normally avoid. These techniques have been found to be effective in decreasing pain and disability in patients with other persistent pain conditions and could be adapted for use in individuals with OA.
The Brief Fear of Movement Scale identified in this study provides a promising and valid approach for assessing fear of movement in OA. This brief scale demonstrated several important strengths including a small number of items, sound psychometric properties, and consistent performance across diverse groups. Future longitudinal and experimental studies are needed to further examine the scale’s stability over time and its sensitivity to change.