Torn discoid lateral meniscus is associated with increased medial meniscal extrusion and worse articular cartilage status in older patients.

Purpose: To compare the clinical, imaging, and arthroscopic characteristics of the torn discoid lateral meniscus (TDLM) in patients greater than 40 years of age with matched controls.

Methods: One hundred and ninety-four older patients (211 knees) who underwent arthroscopic surgery for a TDLM were consecutively recruited (Group 1). Another 211 age- and sex-matched controls with a torn semilunar lateral meniscus were included in this study (Group 2). Statistical analyses were used to determine the differences in the clinical, imaging, and arthroscopic characteristics between the two groups.

Results: In our series, more severe medial meniscal extrusion on magnetic resonance imaging was present in Group 1 than in Group 2 and more serious osteoarthritic changes were observed in both the medial and lateral compartments in Group 1. Under the same conditions, chondral lesions in the knee were more serious in Group 1 than in Group 2 when patients were subgrouped according to the presence of a horizontal tear or complex tear.

Conclusions: In the present study, older patients with a torn discoid lateral meniscus exhibited greater and more severe medial meniscal extrusion and more serious osteoarthritis. Therefore, knees with a discoid lateral meniscus displaying medial meniscal extrusion should be monitored carefully with long-term follow-up, because a medial meniscal extrusion may increase the risk of progression to degenerative osteoarthritis of the medial compartment. Regarding the clinical relevance, these findings will be helpful in further revealing that a torn discoid lateral meniscus may affect not only the cartilage in the lateral compartment but also the cartilage in the medial compartment and medial meniscal extrusion.

Level of evidence: III.