Radiographic evaluation of key anatomical markers in discoid lateral meniscus: a systematic review and meta-analysis.

PURPOSE: The lateral discoid meniscus (DLM), a common anatomical variant in Asian populations, is often linked to knee pain, restricted motion, and an increased risk of meniscal tears. Due to limitations of magnetic resonance imaging (MRI) in certain patients, this study aims to assess the efficacy of X-ray parameters in diagnosing DLM, focusing on key features: lateral tibial spine height (LTSH), lateral joint space distance (LJSD), fibular head height (FHH), lateral tibial plateau obliquity (LTPO), and the condylar cut-off sign. METHODS: A systematic review and meta-analysis were conducted using studies from PubMed, Embase, and Web of Science (January 2004 - October 2024). Studies with observational designs, X-ray measurements, and data on DLM were included. Mean difference (MD) and 95% CI analyses were performed using Review Manager and Stata. RESULTS: Nine studies involving 788 discoid menisci and 761 normal knees were included. LJSD and FHH were significantly larger in the DLM group (MD = 1.18 and - 3.03, P < 0.01), while LTPO was smaller (MD = -2.18, P < 0.01). LTSH did not show significant differences in children but was smaller in adults with DLM (MD = -0.65, P < 0.01). The condylar cut-off sign also showed significant correlation in both adults and children (MD = -0.10, P < 0.01). CONCLUSION: This meta-analysis identifies LJSD, FHH, LTPO, and the condylar cut-off sign as key radiographic markers for diagnosing DLM, with accuracy enhanced when combined, particularly in the absence of MRI. LTSH appears diagnostically relevant mainly in adults, with limited value in pediatric populations. LEVEL OF EVIDENCE: IV.