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 applies elsewhere as well. The classification was initially devised for chondromalacia patella grading.

• 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