Pathology of knee osteoarthritis pain: contribution of joint structural changes and pain sensitization to movement-evoked pain in knee osteoarthritis.

Introduction: Movement-evoked pain (MEP) is the primary symptom in patients with knee osteoarthritis (KOA).

Objectives: This study aimed to investigate the contribution of joint structural changes and pain sensitization to the mechanisms of MEP in patients with KOA.

Methods: A total of 86 patients were assessed for demographic characteristics, osteoarthritis severity, Whole-Organ Magnetic Resonance Imaging Score-Hoffa synovitis and bone marrow lesions, pressure pain threshold and temporal summation of pain at the knee and forearm, Central Sensitization Inventory-9, and MEP. In measure of MEP, knee pain was scored using a numerical rating scale (NRS, 0-10) before and every minute during a 6-minute walking test (6MWT), and the MEP index was defined as the change in NRS pain score from baseline to the sixth minute of walking.

Result: On average, pain during 6MWT increased by 1.4 ± 1.5 points on the NRS relative to baseline, with 30.2% of patients showing an increase of 2 points or more. The hierarchical linear regression analysis revealed that Hoffa synovitis, pressure pain threshold at the forearm, and temporal summation of pain at the knee were associated with the MEP index.

Conclusion: The findings of this study suggest that both synovitis and neural mechanisms, such as pain sensitization, play a role in the development of MEP in KOA.