Lateral meniscus degeneration does not affect short-term outcomes after fixed-bearing medial unicompartmental knee arthroplasty

Purpose Medial unicompartmental knee arthroplasty (UKA) is widely used for isolated medial osteoarthritis, but progression of lateral compartment osteoarthritis remains a common cause of revision. Pre-operative lateral meniscal degeneration on magnetic resonance imaging (MRI) is therefore often considered a potential contraindication. It was hypothesized that such lesions would not impair short-term outcomes after fixed-bearing medial UKA. Methods In this retrospective cohort study, 112 knees in 98 patients (mean age, 72.7 years) who underwent primary fixed-bearing medial UKA with at least 1 year of follow-up were retrospectively reviewed. Hip–knee–ankle (HKA) angle, range of motion (ROM), and 2011 Knee Society Score (KSS) were assessed pre-operatively and at 1 year post-operatively. Pre-operative MRI was used to evaluate the lateral meniscus based on the Mink classification. Knees were divided into two groups: normal and degeneration. Outcomes were compared using the unpaired t test and χ 2 test. Adverse events, including revision and infection, were recorded. Results There were 41 knees in the normal group and 71 in the degeneration group. No significant differences were observed in pre-operative HKA angle, ROM, or 2011 KSS scores. Post-operative HKA angle, ROM, and 2011 KSS scores improved significantly, and improvement scores did not differ significantly between the two groups. No revisions or serious adverse events occurred. Conclusions Pre-operative lateral meniscal degeneration did not adversely affect patient-reported outcomes, ROM, or radiographic findings during the first post-operative year following fixed-bearing medial UKA. Longer-term follow-up studies are required to determine whether these findings remain valid over time.