Evaluation of the morphological variations of the meniscus: a cadaver study.

Purpose: The purpose of this study was to reveal the prevalence of the subtypes of the meniscus using human cadaver knees.

Methods: Four hundred and thirty-seven cadaveric knees in 219 subjects (formalin fixed, Japanese population) with a median age of 83 years (54-97) were included in this study. All soft tissues surrounding the knee, excluding the meniscus, were resected, and macroscopic assessment of the meniscus was performed. Meniscus subtypes were classified as: (1) normal meniscus, (2) complete discoid, (3) incomplete discoid, (4) ring-shaped, and (5) double-layered.

Results: All subtypes of the meniscus were observed in the lateral meniscus. Complete discoid lateral meniscus was observed in 27 knees (6.2%), incomplete discoid lateral meniscus was observed in 139 knees (31.8%), ring-shaped lateral meniscus was observed in 4 knees (0.9%), and double-layered meniscus was observed in 2 knees (0.5%).

Conclusion: This study reports the accurate prevalence of ring-shaped and double-layered meniscus. None of the subtypes were detected in the medial meniscus in this study. For clinical relevance, the results of this study can be useful in assisting the diagnosis of meniscus tear in clinical situations.