Articular Cartilage Defects of the Knee

Overview

  • From trauma, osteochondritis dissecans or instability
  • Surrounding cartilage and alignment preserved, unlike diffuse osteoarthritis
  • Hyaline cartilage has very limited healing capacity
  • Assess size, depth (ICRS), location, alignment, menisci and stability
  • Debridement, microfracture, OAT, osteochondral allograft, ACI or MACI
  • Size, age and demand guide choice, correcting malalignment or instability at the same time

Pathology

Articular Cartilage Defects of the Knee, histology of the zones of articular cartilage
Histology of the zones of articular cartilage. Image by Catherine A. Bautista, Hee Jun Park, Courtney M. Mazur, Roy K. Aaron, Bahar Bilgen, Wikimedia Commons, CC0.
  • Partial thickness defects do not heal
  • Full thickness defects fill with type I collagen fibrocartilage, inferior to type II hyaline cartilage

Classification

Outerbridge

GradeDescription
ISoftening
IIFissuring under 1.3 cm
IIIFissuring over 1.3 cm
IVErosion to subchondral bone

Original publication Outerbridge RE. The etiology of chondromalacia patellae. J Bone Joint Surg Br. 1961;43-B:752-7.

ICRS

GradeDescription
1Superficial
2Under half depth
3Over half depth
4Through subchondral bone

Original publication Brittberg M, Winalski CS. Evaluation of cartilage injuries and repair. J Bone Joint Surg Am. 2003;85-A Suppl 2:58-69.

Investigations

  • Weight bearing Rosenberg view and standing long leg films
  • Cartilage specific MRI for size, depth and subchondral bone

Management

  • Correct malalignment, instability, meniscal deficiency and maltracking first or simultaneously
  • Under 2 cm squared and low demand, debridement, chondroplasty or microfracture
  • Small defects in high demand patients, OATS or mosaicplasty, providing hyaline cartilage and bone
  • 2 to 4 cm squared, microfracture if low demand, or OATS, MACI or allograft if high demand
  • Over 4 cm squared, MACI, or osteochondral allograft with bone loss
  • Patellofemoral defects suit cell based techniques with maltracking correction
  • ACI is two stage, under a periosteal patch (first generation), collagen membrane (second) or on matrix (third)
  • Bipolar lesions, established OA and older age favour arthroplasty

Prognosis

  • Microfracture fibrocartilage deteriorates after several years, especially in large lesions and older patients
  • Osteochondral and cell based grafts last longer in large defects in young patients

Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 10 October 2026.