Focal periphyseal edema zones, also known as FOPE zones, are regions of bone marrow edema seen on MRI that are principally located at the physes about the knee. They are thought to represent potentially painful manifestations of physiologic physeal fusion 1.
FOPE zones are seen in both sexes. They are typically seen in females around the ages of 11-12 and in males around the ages of 13-14 (around the time of expected skeletal maturation) 1.
Clinically, patients may present with pain, with or without a history of acute injury 1.
The exact cause of FOPE zones is unknown. A suggested etiology relates these findings as part of the normal physiologic process of physeal fusion. As the physis of a long bone begins to close, osseous bridging occurs. In some bones that undergo endochondral ossification, it occurs with small bony bars before fusing completely 2,3,5. These may act as anchors to the surrounding bone and alter the local mechanics, producing small amounts of vascular damage and bleeding in physically active adolescents 1.
They have been reported at the distal physis of the femur and at the proximal physis of the femur and tibia 1.
Plain films are unremarkable. These are best seen on MRI. They demonstrate focal regions of increased signal on fluid-sensitive sequences, adjacent to the physis of long bones.
Treatment and prognosis
This entity requires no invasive diagnostic procedure and does not need imaging follow-up 1.
Imaging differential considerations include:
- 1. Zbojniewicz AM, Laor T. Focal Periphyseal Edema (FOPE) zone on MRI of the adolescent knee: a potentially painful manifestation of physiologic physeal fusion?. AJR Am J Roentgenol. 2011;197 (4): 998-1004. doi:10.2214/AJR.10.6243 - Pubmed citation
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