Low Back Pain Flares: How do They Differ From an Increase in Pain?

OBJECTIVE: The term flare is commonly used to describe low back pain (LBP) fluctuations, but individuals with LBP consider that it does not always correspond to increased pain. This case cross-over study aimed to: (1) determine the extent to which days with a flare identified according to a multidimensional definition (self-reported flare, SRF) corresponded to days with greater than average pain (pain-defined flare, PDF) and (2) to investigate whether physical and psychosocial features differ between PDF and SRF. MATERIALS AND METHODS: Individuals with LBP for ≥3 months (N=126) provided data on flares, physical, and psychosocial features daily for 28 days using a smartphone application. RESULTS: Most days with SRF (68%) did not have greater than average pain (ie, PDF), but most days with greater than average pain (64%) were reported as an SRF. On days with SRF-only all physical and psychosocial features were worse than nonflare days. SRF+PDF had lower sleep quality and higher pain intensity, fatigue, disability, pain catastrophizing, and fear avoidance than SRF-only. SRF+PDF had higher pain in the afternoon and evening, disability and pain catastrophizing than PDF-only. Self-efficacy at work and during leisure activities was worse on SRF+PDF days than SRF-only and PDF-only days. DISCUSSION: These findings highlight that when individuals with LBP consider they have a flare, they do not always have greater than average pain, but have worse psychosocial features. This emphasizes that flare has broader dimensions than pain alone. Consideration of flare according to broad dimensions is important when investigating symptom fluctuations across different LBP trajectories.