Is the Meniscus a Type of Cartilage?
Yes, the meniscus is specifically a type of fibrocartilage, distinct from hyaline cartilage found elsewhere in the knee joint. 1, 2, 3
Meniscus Structure and Composition
The menisci are a pair of semilunar (crescent-shaped) fibrocartilaginous structures located in the knee joint that play essential roles in:
- Joint stability
- Weight bearing and load distribution
- Shock absorption
- Improving joint congruity between femur and tibia 3, 4
Composition Characteristics
The meniscus has a unique biochemical composition that distinguishes it from other cartilage types:
- Primary collagen type: Type I collagen (approximately 90% of total collagen) 5
- Secondary collagen type: Type II collagen (in smaller amounts) 5
- Structural organization: Complex network of circumferential fibers enwrapped by a second organizational fibrillar system 5
- Cell population: Metabolically active cells responsive to growth factors, cytokines, and inflammatory mediators 3
Anatomical Distribution
The knee contains two menisci:
- Medial meniscus: More firmly attached at both horns and midbody, making it more susceptible to injury 4
- Lateral meniscus: More mobile with fewer attachments 4
Differences Between Cartilage Types
Understanding the differences between cartilage types helps clarify the meniscus's unique properties:
| Feature | Meniscal Fibrocartilage | Hyaline Articular Cartilage |
|---|---|---|
| Primary collagen | Type I | Type II |
| Collagen organization | Organized network with circumferential fibers | Diffuse without identifiable spatial organization |
| Vascularity | Peripheral zone contains blood vessels | Avascular |
| Function | Weight bearing, stability, shock absorption | Smooth articulating surface |
Clinical Significance
The fibrocartilaginous nature of the meniscus has important clinical implications:
Limited healing capacity: Natural meniscal healing is limited, particularly in avascular zones 6
Degenerative changes: The meniscus is susceptible to matrix fraying and splitting similar to fibrillation seen in hyaline cartilage 2
Imaging considerations: Different cartilage types require specific imaging approaches for proper evaluation 1
Surgical considerations: Recovery after meniscectomy typically takes 2-6 weeks, with weight-bearing restrictions in the first week 7
Understanding that the meniscus is a specialized type of fibrocartilage helps explain its unique biomechanical properties and guides appropriate clinical management of meniscal injuries and degeneration.