Inclusion Criteria:  Knee pain or swelling that has been present for greater than 3 months Knee pain greater than or equal to 3 out of 10 on the visual analog scale Previous radiological evidence (X-ray) of osteoarthritis Age 18 or older  Exclusion Criteria:  Unable to provide consent for enrollment in the study Unable to avoid NSAIDs during the study (must stop 7 days before injection) Age less than 18 Confirmed rheumatologic disease affecting the knee Significant trauma to the knee within 2 months that resulted in pain and/or swelling Active malignancy Pregnancy Local injections to the knee within the last 3 months Previous knee surgery Other causes of knee pain (nerve pain, referred pain, infection of the knee joint, etc) History of platelet disorder History of thrombocytopenia History of severe anemia Severe cardiovascular disease Active infection Immunosuppression/immunodepression Currently taking anticoagulant/antiaggregant History of severe psychiatric disorder with psychosis Assistive device required for household ambulation within the previous 3 months Current IV drug user