A RCT Comparing Dronabinol to a Placebo for Post-operative Pain in Total Joint Arthroplasty

Inclusion Criteria: * Provision of signed and dated informed consent from * Stated willingness to comply with all study procedures and availability to attend all required visits for the duration of the study. * Male or Female * Age 21-75 * Unilateral total knee arthroplasty at Colorado Joint Replacement * All individuals will be screened for drug use (including cannabis) at their preoperative appointment * Ability to take oral medication and be willing to adhere to the dronabinol regimen * For females of reproductive potential: use of highly effective contraception for at least 1 month prior to screening and agreement to use such a method during study participation. * For males of reproductive potential: use of condoms or other methods to ensure effective contraception with partner. Exclusion Criteria: * Narcotic use in the past 6 weeks * Regular cannabis use in the past 3 months * Major depression or anxiety disorders * Documented psychiatric illness (e.g. bipolar, schizophrenia) * Seizure disorder * Current or previous history of drug and alcohol abuse * Known allergic reactions to components of dronabinol * Tobacco use in the past 90 days * Treatment with another investigational drug * Patients that cannot receive spinal anesthesia * Patients that cannot receive the standardized multimodal pain medications (i.e. Tylenol, gabapentin and meloxicam) * Patients that are not able to go home after leaving the hospital and require a short term rehabilitation facility