Abstract
Objective:
To identify predictors of long-term pain and disability in knee osteoarthritis.
Design:
A longitudinal cohort study of five years.
Setting:
Primary care providers.
Subjects:
In all, 108 patients (mean age = 63.6 years, standard deviation (SD) = 7.2 years) with knee pain (⩾40 mm on a 100 mm visual analogue scale in the Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index pain scale) and radiographic grading (Kellgren–Lawrence: 2–4) of knee osteoarthritis who participated in a randomized controlled trial.
Main measures:
Disease-specific pain and functioning were assessed using the corresponding WOMAC subscales. Generic functioning was assessed by the RAND-36 subscales for function and physical and mental component summary scores. Possible baseline predictors for these outcomes were (1) demographic and disease-related variables and (2) psychological variables of mood (anxiety, depression), pain-related cognitions (pain self-efficacy, pain catastrophizing, kinesiophobia), and positive resource factors (life satisfaction, sense of coherence).
Results:
Multivariate linear mixed model analyses revealed that minimal anxiety at baseline predicted significantly better results for pain (WOMAC, P = 0.019) and function (WOMAC, P = 0.001, RAND-36 function P = 0.001). High pain self-efficacy predicted significantly better scores in RAND-36 function (P = 0.006), physical (P = 0.004) and mental (P = 0.001) component summaries. Pain catastrophizing predicted higher pain (P = 0.015), whereas fear of movement predicted poorer functioning in RAND-36 physical (P = 0.016) and mental (P = 0.009) component summaries. Those satisfied with life reported higher scores in RAND-36 function (P = 0.002) and mental component summary (P = 0.041). A low number of comorbidities predicted significantly better results in pain (WOMAC P = 0.019) and function (WOMAC P = 0.033, RAND-36 P = 0.009).
Conclusion:
Anxiety, pain-related cognitions, and psychological resources predict symptoms in knee osteoarthritis in the long term.
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