[A man with a swelling of the knee]. / Een man met een zwelling in zijn knieholte.

A 72-year-old male presented with a dorsomedial swelling of the knee. X-rays showed isolated ossificated cartilage particles. The particles, which were found to be in a popliteal cyst, were surgically removed and analyzed by the pathologist. The diagnosis was synovial osteochondromatosis . Isolated synovial osteochondromatosis inside a popliteal cyst is uncommon.