Lateral meniscal abnormalities do not significantly impact short- to mid-term outcomes after medial UKALateral Meniscus Injuries May Not Affect Knee Surgery Outcomes

To evaluate the effect of lateral meniscus injury on the clinical outcome of medial unicompartmental knee arthroplasty (UKA) for anteromedial osteoarthritis (AMOA), and to provide evidence-based support for clinical decision-making. A systematic literature search was conducted across PubMed, Embase, Cochrane Library, Web of Science, Chinese Biomedical Literature Database (CBM), China National Knowledge Infrastructure (CNKI), Wanfang, and VIP databases from inception to March 1, 2026. Data synthesis and meta-analysis were performed using RevMan 5.4 software. Sensitivity and subgroup analyses were conducted where appropriate, and the certainty of evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. A total of 8 retrospective cohort studies comprising 1,709 patients were included. No significant differences were observed between patients with and without lateral meniscal abnormalities in postoperative knee function scores [standardized mean difference (SMD) = −0.06, 95% confidence interval (CI) (−0.26, 0.14), P = 0.56], postoperative knee range of motion [mean difference (MD) = 0.17°, 95% CI (−1.58°, 1.92°), P = 0.85], or postoperative lateral knee pain [risk ratio (RR) = 1.10, 95% CI (0.32, 3.81), P = 0.89]. Sensitivity analyses showed that the pooled results remained stable. No consistent increase in revision or implant failure or lateral-compartment osteoarthritis progression was identified, although evidence for these outcomes was limited by the small number of events. Available evidence suggests that asymptomatic or mild degenerative lateral meniscal abnormalities may not significantly impair short- to mid-term clinical outcomes after medial UKA in appropriately selected patients with AMOA. Therefore, an asymptomatic lateral meniscal abnormality alone should not necessarily be considered an absolute contraindication to medial UKA. However, these findings should not be extrapolated to symptomatic, unstable, traumatic, or root tears or to patients with advanced lateral-compartment cartilage loss.