Tear Pattern of the Complete Discoid Lateral Meniscus According to Meniscal Morphology

The pattern and distribution of tears for the complete discoid lateral meniscus (DLM) are not well documented.

To investigate the prevalence and pattern of tear types for the complete DLM using magnetic resonance imaging (MRI) and arthroscopic data.

Cross-sectional study; Level of evidence, 3.

We reviewed consecutive series of 1219 patients (1406 knees) who underwent arthroscopic knee surgery for any pathology and were diagnosed with DLM between January 1998 and December 2022. After excluding cases with incomplete DLM (774 knees) and previous history of ipsilateral knee surgery (55 knees), a total of 486 patients (577 knees; mean age, 37.4 years; range, 5-76 years) with complete DLM were evaluated. Preoperative MRI and intraoperative arthroscopic findings were analyzed to classify tears into the following: peripheral tear-including bucket-handle tear; horizontal tear; radial tear; flap tear; and no tear. In addition, preoperative MRI was used to categorize 2 distinct morphological variants of complete DLM: (1) a block-shaped type with a thick blunt free edge; and (2) a wedge-shaped type with a tapering sharp free edge.

When categorized by meniscal morphology, 435 knees (75.4%) were classified as block-type and 142 knees (24.6%) as wedge-type complete DLM. Peripheral tears (66.7%) were the most prevalent in the block type, followed by horizontal tears (22.5%) and radial tears (0.7%). In the wedge type, horizontal tears (43%) were observed most frequently, followed by radial tears (18.3%), peripheral tears (11.3%), and flap tears (5.6%).

A block-shaped morphology was the predominant form of complete DLM in this cohort of operatively treated patients. The wedge-type morphology had a distinctly different tear pattern, with horizontal tears being the most common. While the block type exhibited either a peripheral or horizontal tear, the wedge type was characterized by a greater variation in tear pattern.