There are three types of cartilage:

Hyaline, or articular, cartilage covers the ends of bones to create a low-friction environment and cushion at the joint surface. When cartilage in the joint is healthy, it effectively allows fluid bending/straightening motions and protects the joint against weight-bearing stresses.

Cartilage and Bone are specialised forms of connective tissue. They are both made up of cells embedded in an extracellular matrix. Cartilage is thin, avascular, flexible and resistant to compressive forces. Bone is highly vascularised, and its calcified matrix makes it very strong.

As the cartilage cells die, a group of cells that have surrounded the cartilage model differentiate into osteoblasts. The ostoblasts begin forming bone matrix on the partially degraded cartilage (Bruder and Caplan 1989; Hatori et al. 1995). Eventually, all the cartilage is replaced by bone.

A ligament is an elastic band of tissue that connects bone to bone and provides stability to the joint. Cartilage is a soft, gel-like padding between bones that protects joints and facilitates movement.

• Hyaline – most common, found in the ribs, nose, larynx, trachea. Is a precursor of bone.
• Fibro- is found in invertebral discs, joint capsules, ligaments.
• Elastic – is found in the external ear, epiglottis and larynx.

Physicians have long known conditions associated with unusually dense bones. One, referred to as osteopetrosis (literally, “rock bones”), is typically diagnosed in infants and small children. In osteopetrosis, though, despite being dense, the bones are also unusually brittle.

Your bone density is considered normal. Your score is a sign of osteopenia, a condition in which bone density is below normal and may lead to osteoporosis. Your bone density indicates you likely have osteoporosis.

petrous bone