Dwyer MK, et al. - This study examined THA and TKA patients to determine the post-operative opioid use in these subjects and factors associated with the need for refill prescriptions. The need for refill opioid prescriptions was twice more likely among TKA patients when compared with THA patients. Furthermore, TKA patients were prescribed a greater total Morphine Equivalent Dose (MED) for a longer period of time post-operatively, than THA patients. The requirement for refill was more likely in TKA patients who presented with a comorbidity or were currently being treated for anxiety or depression.