Figure 9.

Chronic patellar osteomyelitis with abscess and sequestrum. A: Sagittal proton-density-weighted image of the right knee shows an abscess cavity in the patella (solid arrow) with a central low-density focus consistent with a sequestrum (dashed arrow). There is also disruption of the anterior cortex with spread of infection into the prepatellar bursa (arrowhead); B: Sagittal T2-weighted image with fat suppression again shows the intraosseous abscess (solid long arrow) with central T2 hypointense sequestrum (dashed arrow) and extension of infection into the prepatellar soft tissues (arrowhead). A knee joint effusion is more apparent on this image (solid short arrow); C: Sagittal T1-weighted post-contrast image shows enhancement of the synovium (solid short arrow) indicative synovitis, likely from intra-articular extension of infection.