Objectives: PainDETECT is a self-report questionnaire that can be used to identify features of neuropathic pain. A proportion of patients with knee osteoarthritis score highly on the PainDETECT questionnaire. This study aimed to determine whether those with a higher "positive neuropathic" score on the PainDETECT questionnaire also had greater pain, hypersensitivity and reduced function compared to individuals with knee OA with lower PainDETECT scores.
Methods: 130 participants with knee OA completed the PainDETECT, Western Ontario and McMaster Universities Arthritis Index (WOMAC) and Pain Quality Assessment Scale (PQAS) questionnaires. Quantitative sensory testing was carried out at three sites (both knees and elbow) using standard methods. Cold and heat pain thresholds were tested using a Peltier thermode and pressure pain thresholds using a digital algometer. Physical function was assessed using three timed locomotor function tests.
Results: 22.3% of participants scored in the "positive neuropathic" category with a further 35.4% in the unclear category. Participants in the "positive neuropathic" category reported higher levels of pain and more impaired function based on the WOMAC questionnaire (P<0.0001). They also exhibited increased levels of hyperalgesia at the knee and upper limb sites for all stimulation modalities except heat pain thresholds at the OA knee. They were also slower to complete two of the locomotion tasks.
Discussion: This study identified a specific sub-group of people with knee OA who exhibited PainDETECT scores in the "positive neuropathic" category. These individuals experienced increased levels of pain, widespread, multi-modality hyperalgesia and greater functional impairment than the remaining cohort. Identification of OA patients with this pain phenotype may permit more targeted and effective pain management.
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