Current definitions of pain do not necessitate tissue damage. This is important because it does justice to the pain patient in whom a nociceptive source is not detectable. However, in conjunction with exciting findings regarding supraspinal pain modulation and a (perceived) failure of identifying nociceptive sources in individual patients, this might have led to a devaluation of the role of nociception for chronic pain. In this review, the relative importance of nociception versus psychological factors for chronic pain is examined by scrutinizing the example of pain present several months following surgical joint replacement for severe osteoarthritis.
In most patients with chronic pain due to severe osteoarthritis, removal of the putative nociceptive source leads to pain elimination/reduction, indicating that their pain depended on nociceptive input. Furthermore, the influence of psychological factors on outcomes following joint replacement for severe osteoarthritis is limited: pain catastrophizing, which is the most consistently identified psychological factor influencing outcome, explains less than 10% of the variance of pain magnitude several months after knee replacement. The influence of psychological factors might be larger for pain disability than for pain magnitude, which could skew the perception of the importance of psychological factors.
It appears that the importance of nociception relative to psychological factors is often underestimated, at least in the instance of pain present several months following surgical joint replacement for severe osteoarthritis. Because this might apply also to other chronic pain patients, in particular those without disability, research should not neglect the investigation of nociceptive mechanisms, in particular how they might be detected clinically.
Integrative Spinal Research Group, Department of Chiropractic Medicine, University Hospital Balgrist and University of Zurich, Zurich, Switzerland
Correspondence to Petra Schweinhardt, Balgrist Campus, Lengghalde 5, 8008 Zürich, Switzerland. Tel: +41 44 510 7381; fax: +41 44 386 57 09; e-mail: firstname.lastname@example.org.