Which thin layer of hard tissue sits between the hyaline articular cartilage and the subchondral bone?

The thin layer of hard tissue that sits between the hyaline articular cartilage and the subchondral bone is called the calcified cartilage. This specialized tissue acts as a transitional zone that provides a smooth interface between the articular cartilage, which covers the ends of the bones in a joint, and the subchondral bone, the layer of bone just below the cartilage.

Calcified cartilage is crucial for the stability and function of joints. It often has a unique matrix composition that includes mineralized collagen fibers, providing both strength and resilience. This layer helps to transfer loads from the cartilage to the underlying bone, facilitating the distribution of stress during joint movements.

Moreover, the presence of calcified cartilage can play a vital role in the overall health of the joint. It aids in preventing the erosion of articular cartilage and supports the maintenance of proper joint function by contributing to the biomechanical properties of the cartilage and bone interface. Any disturbances or abnormalities in this layer can lead to joint-related diseases, such as osteoarthritis.