Does Duloxetine Reduce Sub-Acute Pain After Knee Arthroplasty?

Inclusion Criteria: * Patients with osteoarthritis scheduled for primary tricompartmental total knee arthroplasty with a participating surgeon * Age 25 to 75 years * Planned use of regional anesthesia * Ability to follow study protocol * English speaking (primary outcome obtained via telephone call and secondary outcomes include questionnaires validated in English only) * Patients planning on being discharged home or to a rehabilitation center that has agreed to participate Exclusion Criteria: * Concurrent use of duloxetine or other SNRIs, MAOIs, Tricyclic antidepressants, triptans (sumatriptan, rizatriptan, naratriptan, zolmitriptan, eletriptan, almotriptan, frovatriptan), lithium, buspirone, St. John's Wort * Hepatic insufficiency * Renal insufficiency * Patients younger than 25 years old and older than 75 * Patients intending to receive general anesthesia * Allergy or intolerance to one of the study medications * Patients with an ASA of IV * Chronic gabapentin/pregabalin use (regular use for longer than 3 months) * Chronic opioid use (taking opioids for longer than 3 months) * Patients with major prior ipsilateral open knee surgery