Diagnosis of knee joint invasion in patients with osteosarcoma: the value of direct and indirect MRI findings.

Joint invasion by osteosarcoma can reliably be assessed on preoperative MR images with high sensitivity and specificity.

Particularly direct visualization of intrasynovial tumor tissue, capsular insertion invasion, and destruction of intraarticular bone and cartilage, a combination of highly specific direct signs was valuable, while indirect signs were less predictive and specific.