Assessment of radiographic parameters in diagnosing discoid lateral meniscus: A retrospective MRI-based study

It is difficult to diagnose discoid lateral meniscus (DLM) clinically, and various imaging modalities are employed to aid diagnosis. However, the use of radiographic parameters as a diagnostic tool remains unvalidated. Hence, this study aims to determine the validity of radiographic parameters and their role in diagnosing DLM.

This is a retrospective study of magnetic resonance imaging (MRI)-diagnosed DLM. MRI films were reviewed, and the presence of DLM was identified (Group A). A control group of age-and gender-matched patients with no reported abnormalities in their knees on MRI was identified (Group B). X-ray parameters for all patients were measured, including squaring of the lateral femoral condyle (LFC), lateral joint space (LJS), cupping of lateral tibial plateau (CLTP), lateral tibial obliquity (LTO), fibula head height (FHH), height of the lateral intercondylar spine (LIS) and LFC notching, with normalised ratio (NR) values obtained for LJS and FHH by dividing their respective values against the interepicondylar distance (IED). Data analysis was performed to compare differences between both groups.

A total of 72 patients (36 in each group) were included. Our study showed that Group A had significantly smaller squaring of LFC (p = 0.012), wider LJS (p < 0.01), less CLTP (p < 0.01) and reduced LTO (p < 0.01). However, these same parameters were not significant in historical studies. There were no significant differences in the remaining parameters between Groups A and B. In addition, as compared to historical studies that show significant differences in LJS and FHH when comparing normal menisci versus DLM, our present study did not show a significant difference in the latter parameter.

Widened LJS is a consistent X-ray parameter seen in DLM. Inconsistencies in the significance of other radiographic parameters should drive caution when using them for diagnosis, and other imaging modalities should be utilised to confirm the presence of DLM.

Level III.