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Portrait of Articular cartilage

Anatomy · Joints & cartilage

Articular cartilage

Glassy, smooth and avascular

Joints · bone ends

Articular cartilage is the smooth, glassy hyaline cartilage that covers the ends of the bones in synovial joints. Only a few millimetres thick, it has a very low friction surface and spreads load, and is lubricated and nourished by synovial fluid. It has no blood vessels, nerves or lymphatics, so it heals poorly, and its wear and tear is the hallmark of osteoarthritis.

How to spot them

  • ▸A thin, smooth, white-blue layer capping the bone ends inside a joint
  • ▸No blood vessels, nerves or lymphatics: it feeds by diffusion from synovial fluid
  • ▸Chondrocytes in lacunae within a matrix of type II collagen and proteoglycan
  • ▸Wears in osteoarthritis, exposing bone (eburnation)

What to know

A glassy covering, a few millimetres thick, on the ends of bones inside a joint

Articular cartilage — hyaline cartilage, from Greek hyalos, glass.

It has no blood supply and no nerves, so once damaged it heals poorly and damage is not itself painful

Articular cartilage — avascular, aneural, alymphatic.

It is nourished by fluid from the joint cavity, not by blood

Articular cartilage — nutrition by diffusion from synovial fluid.

Its wearing away is the hallmark of the commonest form of arthritis

Articular cartilage — osteoarthritis.

Its cells sit in small cavities within a matrix rich in type II collagen and proteoglycans

Articular cartilage — chondrocytes in lacunae.

Key ideas

  • Type II collagen provides tensile strength; negatively charged proteoglycans hold water and resist compression.
  • Repair techniques include microfracture and autologous chondrocyte implantation.

Quick-fire facts

  • •It is a form of hyaline cartilage; its cells are chondrocytes.
  • •Typically about 2 to 4 mm thick, varying by joint and site.
  • •About 65 to 80 per cent of it is water.
  • •Its matrix is mostly type II collagen and the proteoglycan aggrecan.
  • •Cartilage has no nerves, so damage is not felt until underlying bone or the synovium is involved.
  • •Loading pumps fluid in and out: movement is essential to nourish it.
  • •Osteoarthritis: gradual loss of articular cartilage, with bone remodelling and osteophytes.
  • •Unlike the meniscus or intervertebral disc, articular cartilage is hyaline, not fibrocartilage.

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