why is cartilage pliable while the bone is rigid

Cartilage is made up of specialized cells known as chondroblasts. These cells secrets large amount of extracellular matrix that contain collagen fibers, substances rich in proteoglycan and elastin fibers that make cartilag soft and flexible. When chondroblasts get embedded in the extracellular matrix they are called as chondrocytes. Chondrocytes and matrix all together form a cartilage.
Bone is made up of osteons, calcium phosphate and some collagen. Calcium phosphate is responsible for its rigidity.