Medial unicompartmental knee arthroplasty: fixed-bearing or mobile-bearing? A narrative review

BACKGROUND: The number of patients undergoing medial unicompartmental knee arthroplasty (MUKA) surgery has increased globally in recent decades. It has become an acceptable alternative to either a high tibial osteotomy or total knee arthroplasty (TKA) for individuals with isolated single-medial compartment knee osteoarthritis (OA). However, the optimal bearing surface design for MUKA remains open to debate. The purpose of this narrative review of the literature was to compare the outcomes of fixed-bearing MUKA (FB-MUKA) and mobile-bearing MUKA (MB-MUKA) as judged by clinical results and subsequent surgical revision rates. Additionally, to determine if trends noted in national arthroplasty registers were following surgical choices based on superior long-term outcomes.METHODS: A literature search was carried out in PubMed (MEDLINE) on 16 January 2026, utilizing as keywords: “UKA mobile-bearing versus fixed-bearing.” Of the 17 articles found, 10 were eventually included because they were most closely related to the topic in question (inclusion criteria). Articles that were not directly related to the subject of this article were excluded (exclusion criteria). In addition, an important reference to the UK National Joint Registry has been added. Therefore, 11 articles were ultimately analyzed.RESULTS: The two most frequent causes of revision were progression of OA in other compartments and aseptic implant loosening secondary to polyethylene (PE) wear; other less common causes for revision were periprosthetic fracture, bearing dislocation, infection, instability and unexplained pain. Both cemented FB-MUKAs and uncemented MB-MUKAs provided acceptable long-term results in cases of single-medial unicompartmental knee OA. The level of evidence of the published articles is low (levels III and IV), with no level I or II studies.CONCLUSIONS: Studies with high level of evidence (I and II) are required to confirm the conclusions drawn in this article. The trends demonstrated in the UK National Joint Registry, chronicled over more than two decades, of increasing favor for either cemented FB-MUKAs and uncemented MB-MUKAs at the expense of cemented MB-MUKAs, which were the dominant medial unicompartmental surgical choice in 2004. However, heterogeneity and implant design variability are key limitations.