Meniscus extrusion on standing weightbearing ultrasound is associated with limb alignment and posterior tibial slope in healthy knees.

Purpose: The purpose of this study was to report meniscus extrusion in asymptomatic knees using ultrasound sonography (US) and evaluate the association between the extrusion and joint space width, coronal alignment, and posterior tibial slope (PTS). Methods: Patients ≥18 years with meniscus allograft transplantation with a contralateral knee that was asymptomatic, Kellgren-Lawrence grade ≤1, without a history of pathology were included. Knee pain or acute injury requiring orthopaedic evaluation, prior knee surgery, and inflammatory arthropathies were excluded. Meniscus position was captured via US in supine, bipodal, and unipodal stances. Participants underwent radiographic imaging, and joint space width, alignment, and PTS were measured. Statistical analyses included Results: Twenty-eight patients (mean age: 39 ± 11 years, 36% females) were included. No significant differences were found between medial and lateral extrusion across stances (all Conclusions: Meniscus extrusion varied with loading conditions and bony morphology. Varus alignment was associated with less lateral meniscus extrusion, and increased PTS with greater medial meniscus extrusion. These results establish baseline values for dynamic meniscus extrusion in healthy knees, to guide US-based monitoring after surgery. Level of Evidence: Level IV, case series.