Postoperative Length of Stay: Comparing Kinematic and Mechanical Knee Alignments in Knee Arthroplasties

Unicompartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA) can be technically accomplished by either traditional mechanical alignment or by an alternative kinematic alignment. The purpose of this study is to compare postoperative length of hospital stay between these two approaches. A retrospective study at Medstar Washington Hospital Center from 2015 – 2024 identified 167 cases of UKAs, of which 69 were kinematic and 98 were mechanical. During the same period, 420 TKAs were identified where 244 were kinematic and 176 were mechanical. Postoperative length of hospitalization and physical therapy recommendations was then compared with two-sample T-tests and Chi-square tests. Patients undergoing a UKA kinematic procedure were discharged a half day earlier than their mechanical counterparts (p = 0.029), and TKA kinematic patients were discharged nearly a full day earlier (p = 0.0001). Additionally, TKA kinematic patients were more likely to be discharged home with home services rather than to a rehabilitation facility for physical therapy (p < 0.00001). UKA patients of both kinematic and mechanical alignment were recommended to be discharged home (p = 0.312) Postoperative length of stay is significantly decreased by up to a day in patients receiving a knee arthroplasty by kinematic alignment approach. TKA kinematic patients also benefit from a discharge recommendation to home for physical therapy, rather than requiring transfer to a rehabilitative facility. These findings highlight how kinematic alignment may contribute to early improved patient satisfaction, restore early functionality, and decrease disease burden. (Journal of Surgical Orthopaedic Advances 34(3):124-127, 2025)

Key words: unicompartmental knee arthroplasty, total knee arthroplasty, postoperative outcomes, kinematic alignment, hospitalization