The knee is joint affected most after the hip.

Risk factors includes steroid use, alcohol abuse, and inflammatory diseases.

Young people, lateral femoral condyle.

80% bilateral, 80% multifocal.

Mechanism is vessel occlusion.

Extension to epiphysis and diaphysis.

MRI is the gold standard.

Rx for joint collapse and monitoring.

Pre-collapse phase: conservative treatment and joint preserving surgery are recommended.

Post-collapse phase: joint arthroplasty.