A 58-year-old male presented to the emergency department with a chief complaint of knee pain and swelling after performing hirudotherapy (leech therapy) approximately one week prior. Knee arthrocentesis demonstrated significant hemarthrosis. Hirudotherapy is being used for a broad array of reasons including treatment of osteoarthritis, to plastic and reconstructive surgery. Case reports and journal articles often discuss cutaneous reactions, bleeding, and infection as common adverse events. Intra-articular bleeding is not commonly mentioned. With hirudotherapy being utilized more as alternative therapy for osteoarthritis and joint pain, physicians should be aware of hemarthrosis as a possible adverse reaction.