[Research progress on the causes of pain in knee osteoarthritis].

Objective: To review the research progress related to pain in knee osteoarthritis (KOA). Methods: A systematic review of relevant research literature at home and abroad in recent years was conducted to analyze the roles played by multi-dimensional factors such as demographics, imaging, serology, bone metabolism, biomechanics, neurological factors, and macrophages in the occurrence and development of KOA pain. The mechanisms of pain induction were expounded and the research directions were prospectively proposed. Results: The occurrence of KOA pain is a complex process interwoven with multiple factors. Demographic factors such as gender, age, and body weight are closely related to its occurrence and pain degree. Structural changes shown by imaging examinations (such as MRI, ultrasound, and X-ray films) can be used to assess the level of pain. A variety of inflammatory factors released by intra-articular inflammation directly participate in the initiation of pain. Bone metabolic factors can also induce pain by influencing changes in bone density. Biomechanical factors are involved in the pain process by altering the concentrated distribution of joint stress. The various mediators released by the local inflammatory response of the joint trigger hyperalgesia and peripheral nerve sensitization through damage receptors, promoting the conduction and amplification of pain signals. The bidirectional interaction between nerves and joints further intensifies the pain. In addition, the expression of certain ion channels, the mediation and release of pain signals by macrophages and osteoclasts, provide a theoretical direction for in-depth exploration of the microscopic mechanism of KOA pain. Conclusion: Future research needs to integrate multiple regulatory mechanisms such as biomechanics, inflammation and neural regulation, systematically explore key intervention targets, in order to deepen the understanding of the pain mechanism of KOA and promote the formation of more comprehensive and precise pain diagnosis and treatment plans.