Talk about interstitial growth of cartilage.

Obsereved in fetus and post-natal growth of long bones, chondroblasts and chondrocytes are divided by mitosis and two or more daughter cells are remained in same lacuna, ensuring expansion of internal mass and synthesis of ECM gets daughter cells apart. May be linear (same direction mitosis axial isogenic group) and increase in size (epiphyseal group) or circular (radial isogenic group) and increases in girth. rare in adults.