The calcified-noncalcified cartilage interface: the tidemark

Area of Science:

• Biochemistry
• Histology
• Orthopedics

Background:

• The tidemark is an interface between calcified and non-calcified cartilage layers.
• It forms due to chondrocyte activity in areas of loading or pulling.
• Its appearance in articular cartilage is linked to skeletal maturation.

Purpose of the Study:

• To define the tidemark using biochemical methods.
• To understand its origin and relationship to mineralization fronts.
• To explore its changes in articular cartilage and transitional zones.

Main Methods:

• Biochemical analysis of cartilage interfaces.
• Histological examination of hyaline and fibrous cartilage.
• Chondrocyte activity assessment.

Main Results:

• The tidemark is better defined biochemically than morphologically.
• It originates from chondrocyte activity between cartilage layers.
• Chondrocytes near the tidemark show positive alkaline phosphatase activity, extending to the periosteum.

Conclusions:

• The tidemark is a specific instance of a broader calcification/mineralization front.
• Its changes reflect the remodeling of the calcified cartilage layer.
• The alkaline phosphatase positivity suggests a continuous biochemical process from the tidemark to the periosteum.