The purpose of the proposed study is to evaluate the efficacy of dronabinol for postoperative pain after arthroscopic surgery of the knee. The investigators hypothesize that dronabinol will relieve pain, reduce opioid consumption and will result in few negative side effects. If this pilot study shows promising results the investigators will expand the trial to include additional arthroscopic surgeries (hip, shoulder) and other types of orthopaedic surgery.