MRI diagnostic performance and strategies for identifying retears in treated pediatric discoid and non-discoid lateral meniscal repairs

Magnetic resonance imaging (MRI) plays a role in assessing retears of previously treated lateral menisci (LM). We aim to characterize the rate and pattern of arthroscopically confirmed LM retears in children with and without discoid morphology. 288 patients (312 knees) who underwent arthroscopic repair of isolated LM tears between 2018 and 2023 were identified. 20 patients (21 knees) had arthroscopically confirmed isolated LM retear. This included 11 retears of discoid lateral meniscus (DLM) and 10 retears of non-DLM. MRI correctly identified retear in 81.8% of DLM cases (n = 9) and 100% of non-DLM cases (overall 90.5%, P = 0.476). 78% of DLM cases (n = 7) had residual discoid elements. MRI is highly accurate in diagnosing retears in isolated LM injuries (90.5%). We suggest that the radiological approach to assessing meniscal retears can be similarly applied to treated discoid and non-discoid menisci. However, special attention to residual discoid elements is crucial in previously treated DLMs.