## Meniscal Anatomy and Injury Patterns ### Meniscal Shape and Attachments **Key Point:** The **medial meniscus** is C-shaped with firm, extensive capsular attachments (including to the MCL), making it relatively immobile. The **lateral meniscus** is O-shaped (nearly complete circle) with loose capsular attachments and a popliteal hiatus, allowing greater mobility. | Feature | Medial Meniscus | Lateral Meniscus | | --- | --- | --- | | Shape | C-shaped (open posteriorly) | O-shaped (nearly complete) | | Capsular attachments | Firm and extensive (fused to MCL) | Loose and mobile | | Popliteal attachment | None | Yes (popliteus muscle) | | Mobility | Low ("trapped" during rotation) | High (can escape during rotation) | | Isolated tear frequency | **Lower** | **Higher** | ### Clinical Significance: Tear Patterns **High-Yield:** Because the **lateral meniscus is more mobile**, it is actually **more commonly torn in isolation** than the medial meniscus. The medial meniscus's firm attachments make it more likely to be torn **in combination with other injuries** (e.g., ACL + MCL + medial meniscus = "unhappy triad"), but isolated medial meniscal tears are less frequent than isolated lateral meniscal tears. **Clinical Pearl:** The popliteus muscle attachment to the lateral meniscus is functionally important—contraction of the popliteus internally rotates the tibia and retracts the lateral meniscus during knee flexion, protecting it from being trapped. ### Why the Correct Answer is Wrong The statement claims "the medial meniscus is more commonly torn in isolation compared to the lateral meniscus." This is **false**. The lateral meniscus is torn more frequently in isolation because of its greater mobility and loose capsular attachments. The medial meniscus is more often torn as part of a multi-ligamentous injury complex. [cite:Clinically Oriented Anatomy 8e Ch 6]
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