Total hip and knee arthroplasties are effective surgical interventions for relieving hip pain and improving physical function caused by arthritis. Although the majority of patients substantially improve, not all report gains or are satisfied after receiving total joint arthroplasty. This article reviews the literature on patient outcomes after total hip and knee arthroplasties for osteoarthritis, and the evidence pertaining to factors that affect these patient-centered outcomes. Mounting evidence suggests that no single patient-related or perioperative factor clearly predicts the amount of pain relief or functional improvement that will occur following total hip or knee arthroplasty.