Illustration of the Outerbridge classification of chondrosis. The diagram demonstrates the classification on patellar cartilage for ease of concept demonstration due to cartilage thickness, but it applies elsewhere as well.
- grade 0 - normal
- grade 1 - cartilage signal abnormality, but appears architecturally intact
- grade 2 - surface fraying or focal defects involving less than 50% of cartilage thickness
- grade 3 - defects involving more than 50% of cartilage thickness, without bone edema
- grade 4 - full-thickness cartilage defect/loss with associated bone marrow edema