Psychosocial factors partially mediate the relationship between mechanical hyperalgesia and self-reported pain

Background and aim: Amplification of sensory signalling within the nervous system along with psychosocial factors contributes to the variation and severity of knee pain. Quantitative Sensory Testing (QST) is a non-invasive test battery that assesses sensory perception of thermal, pressure, mechanical and vibration stimuli used in the assessment of pain. Psychosocial factors also have an important role in explaining the occurrence of pain. The aim was to determine whether QST measures were associated with self-reported pain, and whether those associations were mediated by psychosocial factors.
Methods: Participants with knee pain identified from a population-based cohort completed a tender point count and QST assessments (thermal, mechanical and pressure pain thresholds; wind-up; mechanical pain sensitivity; dynamic mechanical allodynia; vibration detection threshold) at the most painful knee and opposite forearm (if pain-free). Participants were asked to score for their global and knee pain intensities within the past month (range 0 to 10), and complete questionnaire items investigating anxiety, depression, illness perceptions, pain catastrophizing, and physical functioning. QST measures (independent variable) significantly correlated (Spearman’s rho) with self-reported pain intensity (dependent variable) were included in structural equation models with psychosocial factors (latent mediators).
Results: 61 participants (36 women; median age 64 years) with complete data were included in subsequent analyses. Tender point count was significantly correlated with global pain intensity while dynamic mechanical allodynia at the knee and mechanical pain sensitivity and the knee and at the forearm were significantly correlated with both global pain and knee pain intensities. Latent psychosocial mediators were significant partial mediators for tender point (75% total effect), mechanical pain sensitivity (52% total effect) and dynamic mechanical allodynia at the knee (63% total effect) on global pain, and for mechanical pain sensitivity at the knee (35% total effect) on knee pain. Significant partial mediation was observed for pain intensity at the tested knee with knee MPS, but not with DMA at the knee.
Conclusions: Mechanical hyperalgesia was associated with increased knee and global pain indicative of central sensitisation. Psychosocial factors were significant partial mediators, highlighting the importance of central emotional processing in pain perception.
Implications: Associations between mechanical hyperalgesia at the forearm and knee, psychosocial factors, and increased levels of global and knee pain intensity provide evidence of central sensitisation as a key mechanism in knee pain.