Articular Cartilage Damage: Why It Has Limited Self-Repair Capacity

Articular (hyaline) cartilage covering joint surfaces has very limited intrinsic healing ability due to its unique avascular, aneural, and alymphatic nature.

Why It Doesn't Heal Well

• No blood vessels: Nutrients diffuse from synovial fluid; no inflammatory cell influx, no clot formation, no progenitor cell recruitment.
• No nerves: No pain feedback to limit joint loading; no neurogenic inflammation.
• Low cellularity: Chondrocytes comprise 1–2% of tissue volume; trapped in lacunae, cannot migrate.
• Dense extracellular matrix: Collagen type II network + aggrecan resists diffusion and cell movement.
• Low mitotic activity: Chondrocytes rarely divide in adults.

Partial Exception: Defects Penetrating Subchondral Bone

If injury breaches the tidemark and subchondral plate, marrow elements (MSCs, growth factors, blood) enter the defect → forms fibrocartilage (type I collagen) — biomechanically inferior to hyaline (type II), but provides some coverage.

Clinical Implications

• Small defects (<2 cm²) may stabilize; larger ones progress to osteoarthritis.
• Symptomatic lesions often require intervention: microfracture, OATS, ACI/MACI, osteochondral allograft, or emerging biologic scaffolds.
• Prevention: Joint injury avoidance, weight management, neuromuscular training.

Research Frontiers

Tissue engineering (stem cells, hydrogels, 3D printing), gene therapy, and biologics (PRP, BMPs) aim to regenerate true hyaline cartilage.