Background Pain in osteoarthritis (OA) is generally believed to be nociceptive because of local structural pathology and joint failure which so characterizes OA. However, there is often a discordance between the radiographic knee OA and pain, suggesting that the pain can be contributed by other mechanisms other than nociception.1 Recently it is shown that pain in knee OA may have a neuropathic component.2
Objectives The objective of the study was to assess the level of neuropathic pain in patients with knee OA, and identify the clinical and socio-demographical factors associated with neuropathic pain
Study design Cross sectional study.
Setting Medicine and Orthopaedic outpatient department (OPD) of a tertiary care centre located in southern India
Methods One-hundred and sixty-one patients with knee OA satisfying the American College of Rheumatology 1986 clinical and radiographic classification criteria for knee OA were studied. Neuropathic pain was assessed by the Douleur Neuropathique in 4 questions (DN4) questionnaire;3 score of 4/10 or more was classified as diagnostic for neuropathic pain. The Indian version of Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC)4 was used to assess pain, stiffness and physical function of the patients. Factors associated with neuropathic pain were explored.
Results Mean age was 55.7±8.8 years. The mean total Indian WOMAC was 75.07±13.8, WOMAC pain score was 16.1±3.6. Eighty-two patients of 161 (50.9%) had neuropathic pain. When diabetics were excluded (n=58), the proportion of patients with neuropathic pain reduced to 45.6%. The most frequently described pain characteristic was sensation of electric shock (58.4%). Mean total WOMAC and physical function subscale was significantly higher in neuropathic pain group when compared to no neuropathic pain group (DN4 score 3 or less), 77.5±11.5 versus 72.6±15.5, p=0.024; and 54.3±8.8 and 49.8±12.6 respectively, p=0.008
Conclusions Neuropathic pain was seen in up to 50% patients with knee OA. Centrally acting drugs like tricyclic anti-depressants or duloxetine can be used to improve pain and physical function in patients of knee OA with neuropathic pain.
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Disclosure of Interest None declared
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