RESUMO
BACKGROUND: Osteoarthritis arising from cartilage degeneration is the most common cause of joint pain. However, the relationship between joint pain and cartilage degeneration is not well understood. QUESTIONS/PURPOSES: We asked whether the inflammatory mediators participate in the joint pain in the presence of cartilage degeneration. METHODS: We observed electromyographic responses of hindlimb flexors to four inflammatory mediators (bradykinin, ATP, acetylcholine, and serotonin) injected in normal rat knees and in those with monosodium iodoacetate (MIA)-induced arthritis. RESULTS: Joint cartilage of all the rats with MIA-induced arthritis histologically showed severe degeneration. We observed greater magnitude and longer duration responses in the MIA-induced arthritis than normal joints with all four mediators. CONCLUSIONS: The data suggested nociceptors in osteoarthritic joints are more sensitive to inflammatory mediators than in normal joints. Such nociceptive sensitization to inflammatory mediators may participate in the joint pain in osteoarthritis.
