Objective: As the proportion of individuals with diabetes mellitus (DM) in the aging population and the number of total knee arthroplasties (TKAs) both continue to grow, understanding the outcomes for these patient populations is critical. The purpose of this study was to determine whether patients with and without DM differed in the recovery of 3 physical performance measures during the first 90 days following a TKA. Methods: Data collected at ATI Physical Therapy from 169 patients (37 with DM, and 132 without) were available. Physical performance measures included the 4-meter walk test, the 30-second sit-to-stand test (30STS), and the timed-up-and-go test (TUG). A mixed-effects model was performed to determine differences in the rate of recovery and 90-day postoperative scores for all measures. Results: Both groups had similar baseline values for all measures. Patients with DM demonstrated a slower rate of recovery for the 4-meter walk test, and worse scores for the 4-meter walk test, 30STS, and TUG at the end of 90 days when accounting for significant covariates. Conclusion: Our findings show a negative relationship between the presence of DM and the recovery trajectories of all physical performance measures. Clinicians should closely monitor patients with DM, knowing that they are at higher risk for sustained functional deficits and early complications.