Knee cartilage is primarily made of a specialized extracellular matrix (ECM) containing a sparse distribution of cells called chondrocytes. The ECM is a complex structure that gives cartilage its unique properties.
Components of Knee Cartilage:
The key components that make up knee cartilage can be broken down as follows:
Extracellular Matrix (ECM)
The ECM is the main structural component of cartilage. It provides the strength, resilience, and flexibility needed for joint function. The ECM consists primarily of:
- Water: Cartilage has a high water content, which is crucial for its ability to withstand compression and distribute load.
- Collagen: Primarily type II collagen, it forms a network of fibers that provide tensile strength and structure to the cartilage.
- Proteoglycans: These molecules attract and retain water, giving cartilage its hydrated nature and compressive resilience. They also act as lubricants, reducing friction within the joint.
- Noncollagenous Proteins and Glycoproteins: These are present in lesser amounts but contribute to the overall structure and function of the cartilage matrix.
Chondrocytes
Chondrocytes are specialized cells that are sparsely distributed within the ECM. They are responsible for:
- Synthesizing and maintaining the ECM: Chondrocytes produce and regulate the components of the extracellular matrix, ensuring its health and function.
- Repairing damaged cartilage: Chondrocytes play a crucial role in cartilage repair, although their capacity for regeneration is limited.
Detailed Breakdown:
| Component | Function |
|---|---|
| Water | Provides hydration, facilitates nutrient exchange, and helps with compressive resilience. |
| Collagen | Provides tensile strength, forms the structural framework. |
| Proteoglycans | Attract and retain water, giving cartilage its hydrated nature and compressive strength, reduce friction. |
| Chondrocytes | Maintain and repair the extracellular matrix, produce collagen and proteoglycans. |
| Other proteins/glycoproteins | contribute to the overall structural and functional integrity of the ECM |
Practical Insight:
Understanding the composition of knee cartilage is essential for comprehending its function and how it is affected by injury and disease. Damage to the ECM, or dysfunction of the chondrocytes, can lead to conditions like osteoarthritis, where the cartilage breaks down causing pain and stiffness.
