Total joint replacement is a surgical procedure with profound impact on patients’ activity and quality of life, and this surgical procedure is highly utilized on both sides of the Atlantic. Due to new payment models in the United States and cost-constraints in the NHS, eligibility criteria are now being used by physicians to determine who may receive total joint replacement. I will explore the ethics of patient selection to improve outcomes; specifically, screening patients by body mass index to determine eligibility for total joint replacement. I argue that this type of screening is not ethically defensible, and that the creation of eligibility cutoffs is likely to lead to unfair restrictions on who receives total joint replacements.