A mechanism-based pain sensitivity index to characterize knee osteoarthritis patients with different disease stages and pain levels

Background In a cohort of well‐characterized patients with different degrees of knee osteoarthritis (OA) and pain, the aims were to utilize mechanism‐based quantitative sensory testing (QST) to (1) characterize subgroups of patients; (2) analyse the associations between clinical characteristics and QST; and (3) develop and apply a QST‐based knee OA composite pain sensitivity index for patient classification. Methods Two hundred seventeen OA pain patients and 64 controls were included. Kellgren and Lawrence (KL) grading scores were obtained, and pressure pain thresholds (PPTs), temporal summation of pain to repeated painful pressure stimulation and conditioning pain modulation (CPM) were assessed. Associations between pain score/area/duration, radiological findings and QST‐related parameters were analysed. A pain sensitivity index was developed and applied based on PPT, temporal summation and CPM. z‐Score, as statistical tool, was calculated for statistically comparing the pain index of a single patient with a healthy control group. Results High knee pain associated with low KL grade showed particular signs of pain sensitization. Patients showed significant associations between clinical knee pain intensity/duration and lowering of knee PPTs (p