Location of medial collateral ligament tears: introduction to a magnetic resonance imaging-based classification.

Purpose: Despite established tear grade classifications, there is currently no radiological classification for sMCL tear locations. This study aims to establish a magnetic resonance imaging (MRI) tear location classification system for sMCL tears, to enhance understanding and guide treatment decisions by categorizing tear types.

Methods: A retrospective search in a single institution's MRI database identified patients with acute, Grade III sMCL tears (< 30 days between injury and MRI) from January to December 2022. Non-acute and partial tears were excluded, and three observers assessed tear types based on the proposed sMCL MRI tear location system: type I (proximal 25%), Ib (proximal femoral bony avulsion), II (midsubstance, 25-75%), III (distal 25%), IIIb (distal tibial bony avulsion), IIIs (Stener-like lesion). The interclass correlation coefficient (ICC) was used to assess interrater and intrarater reliability for continuous data; Fleiss and Cohen's kappa assessed interrater and intrarater reliability for categorical data.

Results: MRI scans of thirty patients with diagnosed sMCL injuries (53% female, mean age 37 ± 13 years, range 16-68 years) were included based on inclusion/exclusion criteria. Interrater reliability was excellent (ICC: 0.968, 95% CI, 0.933-0.985), and intrarater reliability was excellent (ICC: 0.938, 95% CI: 0.874-0.970 & 0.900, 95% CI, 0.789-0.952). Type I injuries were most common (60%), followed by type III (33.3%), type II (3.3%), type Ib (3.3%), type IIIb (0.0%), and type IIIs (0.0%).

Conclusion: The presented MRI-based sMCL tear location classification provides a reproducible system for grading high-grade sMCL injuries. We propose that this framework will significantly unify tear location understanding and support more informed treatment decisions.