Inactivation of the FAAH (Fatty Acid Amide Hydrolase) enzyme has been shown to relieve pain and inflammation in animal studies. PF-04457845 has been shown to inactivate the FAAH enzyme in animals and healthy human volunteers. The purpose of this study is to evaluate whether PF-04457845 can inactivate the FAAH enzyme in patients experiencing pain due to OA and whether this results in these patients experiencing less pain.