Osteoarthritis pain has a significant neuropathic component: an exploratory in vivo patient model.

Osteoarthritis is the most common form of arthritis and includes manifestations of both nociceptive and neuropathic mechanisms. Intravenous lignocaine, a sodium channel blocker and neuronal membrane stabiliser, has been shown in controlled trials to be effective in neuropathic pain; however, the outcome of intravenous lignocaine in osteoarthritis patients has not been assessed yet. The existence of a neuropathic component to the pain of osteoarthritis was investigated by examining possible benefits upon sensory aspects of pain in osteoarthritis patients receiving intravenous lignocaine therapy. Retrospective observational study was carried out using health data routinely collected for non-research purposes. Patients with generalised osteoarthritis who had not responded to more conservative treatments were recruited sequentially and scheduled for intravenous lignocaine therapy either in the rheumatology or pain relief departments. Assessment of efficacy was carried out through a questionnaire including sensory, psychological and social aspects of pain. The sample consisted of 17 women (60.7%) and 11 men (39.3%) with an average age at the time of treatment of 59 ± 11 years. The average pain relief calculated from the NRS scores was 30.2 ± 21.4%, and the mean duration of pain relief was 10 ± 6 weeks. Pain intensity (p < 0.001), pain relief (p < 0.003) and mobility (p < 0.003) were all significantly improved after administration of lignocaine intravenous infusion therapy. Pain was significantly reduced in a group of osteoarthritis patients after administration of intravenous lignocaine. This suggests that part of the pain mechanism in this patient group may be neuropathic, appears to contribute significantly to the patients' pain, and requires further investigation in studies designed specifically for the purpose.