# Association between discoid lateral meniscus and medial meniscus posterior root tear: A retrospective cohort study

## TL;DR

This study found that people with a discoid lateral meniscus are more likely to have a medial meniscus posterior root tear, but their recovery after surgery is similar to others.

## Contribution

The study is the first to report a significant association between discoid lateral meniscus and medial meniscus posterior root tears.

## Key findings

- The incidence of discoid lateral meniscus was significantly higher in the medial meniscus posterior root tear group.
- Patients with discoid lateral meniscus and medial meniscus posterior root tears had similar clinical outcomes after surgery as those without discoid lateral meniscus.
- Both groups showed significant improvement in clinical outcomes one year after surgery.

## Abstract

Medial meniscus (MM) posterior root tear (PRT) has gained increasing attention because of its biomechanical impact and rapid progression to osteoarthritis. Identifying the risk factors for MMPRT is essential for early diagnosis. Although the discoid lateral meniscus (DLM) is a common congenital variant, no studies have reported on the relationship between MMPRT and DLM. This study aimed to examine the relationship between MMPRT and DLM.

This retrospective cohort study included 94 matched knees that underwent arthroscopic surgery between 2015 and 2021 (58 with MMPRT and 36 with other MM injuries). The matching was performed according to age and sex. Morphological analysis of the lateral meniscus (LM) was performed using coronal magnetic resonance imaging (MRI). DLM was defined as an LM ratio (LM width/tibial width) > 0.20. LM width, LM ratio and DLM prevalence were compared between the two groups. In the MMPRT group, subgroup analysis compared the preoperative and 1‐year postoperative clinical outcomes between patients with and without DLM.

The PRT group showed significantly greater LM width (12.6 ± 3.1 mm vs. 11.1 ± 2.2 mm; p = 0.03) and LM ratio (0.18 ± 0.04 vs. 0.16 ± 0.03; p = 0.01) compared with the other group. The incidence of DLM was also significantly higher in the PRT group (29.3% vs. 8.3%; p = 0.02). No significant differences in clinical scores were observed between the two subgroups either preoperatively or 1 year postoperatively. However, both groups demonstrated significant improvement in all clinical outcomes 1 year postoperatively (p < 0.01).

DLM was significantly more prevalent in patients with MMPRT than in those with other MM injuries. Favourable clinical outcomes were achieved following pullout repair in MMPRT knees regardless of the presence of DLM.

Level III, retrospective cohort study.