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.