Lateral and patellofemoral compartment osteoarthritis progression after medial unicompartmental knee arthroplasty: A five- to 10-year follow-up study Abdulhamit Misir a, ⁎, Erdal Uzun b , Turan Bilge Kizkapan c , Ali Eray Gunay d , Mustafa Ozcamdalli e , Kazim Husrevoglu d a Health Sciences University Gaziosmanpasa Taksim Training and Research Hospital, Department of Orthopaedics and Traumatology, Istanbul, Turkey b Erciyes University Faculty of Medicine, Department of Orthopaedics and Traumatology, Kayseri, Turkey c Bursa Cekirge State Hospital, Department of Orthopaedics and Traumatology, Bursa, Turkey d Health Sciences University Kayseri City Hospital, Department of Orthopaedics and Traumatology, Kayseri, Turkey e Ahi Evran University Faculty of Medicine, Department of Orthopaedics and Traumatology, Kirsehir, Turkey article info Article history: Received 20 January 2020 Received in revised form 23 March 2020 Accepted 29 May 2020 Background: The purpose of the study was to evaluate lateral and patellofemoral osteoarthritis (OA) progression after medial unicompartmental knee arthroplasty (UKA) and identify factors affecting the progression that were not identified previously. Methods: We evaluated 146 patients who underwent medial UKA between 2009 and 2014. Kellgren–Lawrence grading of lateral and patellofemoral OA was performed on preoperative and final follow-up knee radiographs. Radiographic and clinical characteristics, SF-36, and Ox- ford knee scores were compared between the OA progressed and non-progressed groups. Risk factors for lateral and patellofemoral OA progression were evaluated. Results: The lateral OA progressed and non-progressed groups significantly differed in side, preoperative flexion contracture, preoperative joint line convergence angle, postoperative tibiofemoral angle, insert size, revision status (P b 0.05), and the patellofemoral OA progressed and non-progressed groups significantly differed in age, pre- and postoperative flexion contrac- ture, postoperative tibiofemoral angle and pre- and postoperative patellofemoral OA grade (P b 0.05). At the final follow-up, Visual Analogue Scale, Oxford Knee Scores, and SF-36 sub- scores were significantly better in the lateral OA non-progressed group (P b 0.001). Dominant leg (odds ratio (OR): 2.759), insert size (N 4, OR: 2.219), revision status (+, OR: 6.692), and postoperative tibiofemoral angle (N 5.5°, OR: 1.177) were independent risk factors for lateral OA progression, whereas age (N 60 years, OR: 3.222), preoperative patellofemoral OA grade (N 1, OR: 2.085), and postoperative flexion contracture (N 10°, OR: 1.919) were those for patellofemoral OA progression. Conclusions: Mild radiographic progression of 1 KL grade is frequently seen five to 10 years after medial UKA. Postoperative outcomes are significantly affected by lateral compartment OA progression but not by patellofemoral OA progression. © 2020 Elsevier B.V. All rights reserved. Keywords: Unicompartmental Lateral Patellofemoral Progression Osteoarthritis Risk factor The Knee 27 (2020) 1135–1142 ⁎ Corresponding author at: Health Sciences University, Gaziosmanpasa Training and Research Hospital, Karayollari Mah. Osmanbey Cad. 621. Sk. 34255 Gaziosmanpasa, Istanbul, Turkey. E-mail address: misirabdulhamitmd@gmail.com. (A. Misir). https://doi.org/10.1016/j.knee.2020.05.021 0968-0160/© 2020 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect The Knee