Summary

This systematic review found that patients with meniscal root tears had significantly greater medial meniscal extrusions compared to patients with non-root meniscal tears and no tears, with patients that have a greater medial meniscal extrusion having increased risk of developing knee osteoarthritis.

Abstract

Background

Medial meniscal extrusions (MME) had garnered significant interest due to its correlation with medial meniscal root tears and its potential as a diagnostic tool and significance in the progression of knee osteoarthritis.

Purpose

To systematically review and compare if medial meniscal root tears have significantly increased MME compared to non-root tears and no tears and the clinical outcomes related to MMEs.

Methods

An electronic search of PubMed, Embase, Scopus, Web of Science and Cochrane Central Register of Controlled Trials was conducted on June 6, 2022 in accordance with the Preferred Reporting Items for Systematic review and Meta-Analyses (PRISMA) 2020 checklist criteria. The search was conducted using the keywords: Meniscus Tear and Extrusion. No restrictions were placed on the date of publication. The methodological quality of each included article was assessed using the Newcastle-Ottawa Scale (NOS) for assessment of non-randomized studies in meta-analyses. All 23 included studies were of good quality according to the Newcastle-Ottawa scale, with a mean score of 8.48 (range 8-9). All statistical analyses were performed using the Review Manager version 5.3 (Revman, Cochrane Information Management System) software. Random effects models were used in all meta-analyses. Subsequent quality and sensitivity assessments were conducted on included studies to evaluate for potential sources of heterogeneity.

Results

A total of 23 studies involving 7982 knees were included. Compared to non-root tears, medial meniscal root tears had a 1.12 mm (p=<0.001) greater mean absolute meniscal extrusion and was 2.51 times (p=<0.001) more likely to have major MME. Compared to no tears, medial meniscal root tears had a 2.13 mm (p=<0.001) greater mean absolute meniscal extrusion. Within patients with medial meniscal root tears, Widely Displaced medial meniscal root tears had a 1.01 mm (p=<0.001) greater absolute meniscal extrusion compared to Non-Displaced medial meniscal root tears. Patients who had knee osteoarthritis (OA), reported a 0.79 mm (p=<0.001) greater absolute meniscal extrusion compared to patients without knee OA. Patients with knee OA were also 3.86 times (p=<0.001) more likely to have major MME compared to patients without knee OA. A further subgroup analysis revealed that within patients that were not stratified according to medial meniscal root tears, non-root tears or no tears, patients who eventually developed OA had a 0.81 mm (p=0.002) greater absolute meniscal extrusion than those who did not have OA.

Conclusion

Patients with medial meniscal root tears have higher medial meniscal extrusion compared to other types of meniscal tears and those without any meniscal tears. At baseline, patients who had knee osteoarthritis were more likely to have higher meniscal extrusion compared to patients who did not have knee osteoarthritis. Given the results, the authors recommend that meniscal extrusions be routinely measured in patients to aid with diagnosing, decision-making and prognostication for patients with medial meniscal root tears.