Background: Although there is extensive literature supporting a high success rate, there are limited data on return to work after total knee arthroplasty (TKA). Questions/purposes: We sought to determine (1) the percentage of patients who returned to work after TKA; (2) what percentage returned to their original job; (3) whether this varied based on the physical job demand category; and (4) whether there were differences between men and women in terms of the likelihood of returning to work after TKA. Methods: A multicenter study was conducted of patients of working age (18-60 years) who underwent TKA 1 to 5 years previously. An independent third-party survey center with expertise in collecting healthcare data for state and federal agencies collected the data. Definitions from the US Department of Labor's Dictionary of Occupational Titles were used to determine physical job demand categories of sedentary, light, medium, heavy, and very heavy. Complete data were collected on 661 patients undergoing TKA (average age 54 years, 61% women). Results: Seventy-five percent (494 of 661) were employed in the 3 months before their TKA and 98% (482 of 494) returned to work after surgery; 89% (440 of 494) returned to the same job. Before surgery, physical demand categories of the patients' jobs were sedentary 12%, light 10%, medium 24%, heavy 24%, and very heavy 30%. The return to work rate for those employed during the 3 months before surgery by physical demand category was sedentary 95%, light 91%, medium 100%, heavy 98%, and very heavy 97%. Men were more likely than women to have worked within the 3 months before TKA but there was no difference between sexes in return to work after TKA. Conclusions: In this group of young patients, most returned to work at their usual occupation after TKA. Level of Evidence: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.