CorpusHuman Anatomy
SkeletalCartilage

Articular cartilage

Cartilago articularis

Also known as: joint cartilage

A layer of hyaline cartilage, 2–4 mm thick in large joints, covering the articular surfaces of synovial joints. It provides a smooth, almost frictionless, load-distributing bearing surface.

Long Bone — Structure Synovial Joint — Structure

Overview

Thickness (knee, hip)≈2–4 mm (patella up to ≈6–7 mm)
Water content≈70–80%
Friction coefficient≈0.001–0.01

Articular cartilage is a specialised hyaline cartilage with no perichondrium, blood vessels, lymphatics or nerves. Its matrix is ≈70–80% water held by large proteoglycan aggregates (aggrecan bound to hyaluronan), which give it compressive stiffness through their fixed negative charges, and a meshwork of type II collagen that resists tension. It is organised in zones: a superficial (tangential) zone with flattened cells and fibres parallel to the surface (resists shear; lubricin-coated surface), a middle (transitional) zone, a deep (radial) zone with columns of cells and vertical fibres, and the calcified cartilage layer separated from the deep zone by the tidemark and anchored to subchondral bone.

Chondrocytes are nourished by diffusion from synovial fluid, aided by intermittent loading. Because it is avascular and its chondrocytes divide very little, articular cartilage has a very limited capacity for repair: full-thickness defects heal only with mechanically inferior fibrocartilage. In the temporomandibular and sternoclavicular joints the articular surfaces are covered by fibrocartilage instead.

Location

Articular surfaces of bones in synovial joints.

Parts & subdivisions

  1. Superficial (tangential) zone
    Flattened chondrocytes; collagen parallel to the surface; resists shear.
  2. Middle (transitional) zone
    Rounded cells, oblique collagen; resists compression.
  3. Deep (radial) zone
    Columns of cells, vertical collagen; highest proteoglycan content.
  4. Tidemark and calcified cartilage
    Mineralised layer anchoring cartilage to subchondral bone.

Anatomy

Arterial supply

Avascular — nourished by diffusion from synovial fluid (and, in children, from subchondral vessels).

Histology

Hyaline cartilage without perichondrium; chondrocytes in lacunae, often in isogenous groups; type II collagen, aggrecan.

Function

  • Provides a smooth, low-friction articular surface
  • Distributes loads and reduces peak stresses on subchondral bone
  • Acts as a shock absorber through fluid pressurisation

Clinical significance

Osteoarthritis

Proteoglycan loss and collagen network damage lead to fibrillation, fissuring and eventual exposure of eburnated subchondral bone, with osteophytes and subchondral cysts.

Osteochondritis dissecans

A fragment of articular cartilage and subchondral bone separates — classically the lateral part of the medial femoral condyle in adolescents — causing locking.

Compiled from standard anatomy and physiology references — see the Skeletal System sources. For education only; not medical advice.