Investigators do not expect serious adverse events (SAEs) but are well equipped to manage them. Investigators have not seen significant adverse events in combined (UW Radiology and Sports Medicine) clinic use of PRP. Subjects with reactions to acetaminophen or injections have the option to call study personnel at any time. The PI and the primary Co-Investigator will share on-call duty for subjects with adverse events through a pager on a 24/7 basis. Subjects who require significant evaluation and care will be referred to the UW Hospital Emergency Department.