Epidemiology
More common in children and adolescents, especially in the proximal humerus and proximal femur. It is often found after a fracture of the proximal humerus or proximal femur, so the mechanical risk matters more than the diagnosis on its own.
Basic features
A fluid-filled cavity within the bone; it may first appear as a pathologic fracture.
Usual treatment
Observation if the risk is low. Injection, curettage, grafting, or fixation if there is a risk of fracture or an established fracture.
Outcomes and prognosis
It can recur while the skeleton is still growing —recurrence is more frequent in young children and active cysts—, but many lesions become inactive with maturity. It does not become malignant.