Objective: Osteoarthritis is a degenerative disease that affects synovial joints.Micro-injuries of articular structures initiate inflammatory processes,leading to persistent pain.Due to various risk factors,osteoarthritis is often diagnosed in multimorbid patients.This makes pain management one of the key challenges,with a consistent need for new therapeutic strategies.Hence,complementary and integrative methods such as hirudotherapy have become increasingly important,even though their mechanisms of action are not entirely understood.Methods: We retrospectively analyzed the longitudinal effect of a single leech application on osteoarthritic joints in a heterogenic cohort of 24 cases with various chronic pain syndromes.We assessed articular pain intensity ratings and movability of the treated joint after one-time leeching for up to 12 months.We further investigated the effect of hirudotherapy on the systemic pain status and multimodal treatment strategies of the patients.Results: There was a significant reduction in pain intensity ratings at the joint of leech application for up to 12 months after treatment.The improvements in pain intensities were independent of the form of osteoarthritis treated.In addition,we saw a considerable enhancement in local movability of the treated joint.Hirudotherapy did not seem to influence the systemic pain status as well as the previously established individualized multimodal treatment model of the patients.Conclusion: Leeching as an adjuvant therapy has a great potential especially in terms of safety and long-term outcome.