Multiple psychological factors predict pain and disability among community-dwelling knee osteoarthritis patients: a five-year prospective study

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.