The Role of Varus Stress Magnetic Resonance Imaging in the Diagnosis of Medial Meniscal Posterior Root Tear

Abstract

Background: Meniscal root tears represent a significant challenge in knee pathology. This study aimed to standardize MRI techniques for posttraumatic medial meniscal tears and assess the efficacy of varus stress MRI in diagnosing medial meniscal posterior root tears (MMPRT) by quantifying the true extent of meniscal extrusion.

Methods: This single-center prospective study, conducted from January to December 2023, involved 81 patients (62 male, 19 female; age 18-65) with posttraumatic medial knee pain. Patients were categorized as acute, subacute, or chronic based on injury duration. All participants underwent both conventional and varus stress knee MRI. The findings for MMPRT were compared with arthroscopic results to determine diagnostic accuracy.

Results: The application of varus stress significantly improved diagnostic accuracy for MMPRT. In pre-varus MRI, there were 31 true positives and nine false negatives. In the post-varus position, true positives increased to 38, while false negatives decreased to two, with no false positives in either technique. Medial meniscal extrusion (MME) was the most frequent sign, with a detection rate of 65%. The varus stress technique identified 100% of patients with significant MME (≥ 3 mm), a substantial increase from the 53.8% detected by standard MRI (P < 0.05). A highly significant increase in the degree of MME was observed in the post-varus MRI across all chronicity groups (P < 0.0001). Furthermore, the varus stress maneuver resulted in a significant narrowing of the medial joint space and widening of the lateral joint space.

Conclusion: MRI with varus stress technique is used in determining the precise degree of actual extruded meniscus in MMPRT and in evaluating the existence of MME in non-extruded pre-varus MRI. The medial meniscal extrusion is strongly associated with meniscal root tears.