The Outerbridge classification is a grading system for joint cartilage breakdown in the patella.

Outerbridge Grade 0 cartilage - normal patellar cartilage

Normal joint cartilage of femur (below) and patella (above) in the knee joint. Grade 0 on the Outerbridge scale

Outerbridge Grade I - Chondromalacia or softening of the patellar cartilage

Grade I - softening of the patellar cartilage, which can be dimpled with a rounded probe.

Outerbridge Grade IV - patellar cartilage fibrillated with exposure of underlying bone in the tibia

Grade III damage of the patella on the same grading system. The patellar cartilage has become fibrillated and note that the tibia is showing exposed yellowish bone, which would be a grade IV.


Grading joint cartilage damage (Outerbridge)

By recording the Grade, the surgeon will have a simple record for later comparison in case of deterioration or improvement in the joint cartilage.

  • Grade 0 - normal
  • Grade I - cartilage with softening and swelling
  • Grade II - a partial-thickness defect with fissures on the surface that do not reach subchondral bone or exceed 1.5 cm in diameter
  • Grade III - fissuring to the level of subchondral bone in an area with a diameter more than 1.5 cm
  • Grade IV - exposed subchondral bone

What is chondromalacia?

This word causes a lot of confusion in the literature.



The Outerbridge Classification Predicts the Need for Patellar Resurfacing in TKA. Rodríguez-Merchán EC and Gómez-Cardero P. Clin Orthop Relat Res. 2010 May; 468(5): 1254–1257.

Imaging of articular cartilage. Paunipagar BK and Rasalkar DD. Indian J Radiol Imaging. 2014 Jul-Sep; 24(3): 237–248.

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

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