Functional outcomes before amputation, at the casting visit before prosthesis fitting, 1, 6 and 12 months after prosthesis fitting: (a) 2-minute walk test scores at the casting visit before prosthesis fitting (pre-prosthesis) and at 1 month (1 mo), 6 months (6 mo) and 12 months (12 mo) follow-up after prosthesis fitting; (b) 2-minute walk test scores for patients separated by the reason for amputation at pre-prosthesis, 1 mo, 6 mo and 12 mo; (c) Physiologic Cost Index (PCI) at pre-prosthesis, 1 mo, 6 mo and 12 mo and (d) PCI for patients separated by the reason for amputation at pre-prosthesis, 1 mo, 6 mo and 12 mo.