Objective: The aim of this study was to determine which type of knee arthroplasty is easier to forget by comparing levels of joint awareness evaluated with the Forgotten Joint Score (FJS-12) after unicondylar versus total knee arthroplasty. Methods: Patients who underwent either unicondylar or total knee arthroplasty due to primary gonarthrosis were retrospectively identified and then divided into 2 groups: the TKA group (218 patients; mean age = 68.93 ± 7.14 years) and the UKA group (131 patients; mean age = 60.39 ± 7.03 years). The status of joint awareness after knee replacement surgery was assessed using the Turkish version of the FJS-12 at the final follow-up by telephone interview. Also, The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and The EuroQol five-dimensional (EQ-5D) scores were obtained to assess the clinical status of the patients. Results: The mean follow-up was 2.8 years (range = 24–49 months) in the TKA group and 3.2 years (range = 24–50 months) in the UKA group. The FJS-12 was significantly higher in the UKA group (73.60 ± 9.95) than in the TKA group (64.88 ± 9.47) (P = .001). The WOMAC score was significantly better in the UKA group (81.39 ± 9.84) than in the TKA group (74.92 ± 9.99) (P = .001). No significant difference in EQ-5D existed between the groups (0.76 ± 0.14 for the TKA group, 0.79 ± 0.17 for the UKA group; P = .441). In terms of gender, the FJS-12 showed no differences between the groups; however, more favorable scores were recorded in younger patients with UKA. Conclusion: The results of this study have demonstrated that UKA may be better than TKA in terms of the patient perception of pain, stiffness, and physical functioning. Level of Evidence: Level IV, Therapeutic Study Cite this article as: Ateş Y, Akdoğan M, Atilla HA. Which knee replacement do the patients forget? Unicondylar or total knee arthroplasty. [published online ahead of print, 2021 September 9]. Acta Orthop Traumatol Turc; 10.5152/j.aott.2021.20173. 55(5): 417–421.