Introduction: Partial knee arthroplasty (PKA) theoretically produces less blood loss compared to total knee arthroplasty (TKA) due to a lesser invasive procedure. Medial unicompartmental knee arthroplasty (UKA) is the most common PKA performed due used due to the most commonly impacted medial knee. This study compared the postoperative drainage volume and length of stay (LOS) of TKA vs UKA and evaluated its comparison with patient characteristics. Method: This was a retrospective case-control study of 120 patients underwent primary TKA and UKA between December 2019 and October 2022 in a single center. Post-operative suction drainage production volume and length of stay were evaluated for both groups and compared with patients' body mass index (BMI). This was a level III study based on the evidence. Results: Mean total drainage volume of TKA (433.36 ± 224.68 mL) significantly higher than UKA (224.30 ± 126.19 mL) (P < 0.0001). All UKA drainage was removed at day 3 at maximum compared to TKA at day 5. The median LOS in the TKA group was 4 days (3-6 days) which was statistically longer than UKA LOS which was 3 days (3-4 days) (P < 0.0001). WOMAC and VAS score for both groups were found comparable. Conclusions: UKA produces less volume drainage and faster LOS compared to TKA. We found that patients with BMI >25 produce more volume drainage in TKA and longer LOS in both TKA and UKA. Further study evaluating the long-term outcome is needed. © 2024 The Author(s). Published by Wolters Kluwer Health, Inc.