The purpose of this study is to evaluate the impact of using a smartphone application (app) reminder on medication adherence twice daily in 200 adults prescribed 81 milligrams of aspirin (ASA) for 35 days as anti-thrombotic therapy after knee or hip arthroplasty. The aim is to determine if an app downloaded on a smartphone that reminds patients twice a day to take their ASA as prescribed will improve ASA adherence and clinical outcomes for patients after total knee and total hip joint arthroplasty compared to those in the usual care.