title: Expansile subchondral degenerative bone cyst secondary to osteoarthritis.
abstract: A 53-year-old man known to have osteoarthritis of the left knee was examined because of a soft-tissue swelling overlying the pes anserinus tendon. Plain radiography and computed tomography revealed an expansile subchondral cyst of the proximal tibia. The cyst was multiloculated, had a sclerotic margin and an extraosseous soft-tissue component, and interrupted the cortex. Proof of a degenerative cyst was obtained by open biopsy. Such presentation in the knee is rare. Awareness of the possible aggressive behaviour of such degenerative cysts should help avoid confusion with neoplasm.
authors.affiliation: Department of Radiology, O.E. Ospedali Galliera, Genoa, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Bianchi
authors.forename: I F
authors.initials: IF
authors.lastname: Abdelwahab
authors.forename: A
authors.initials: A
authors.lastname: Zwass
authors.forename: F
authors.initials: F
authors.lastname: Rettagliata
authors.forename: E
authors.initials: E
authors.lastname: Federici
authors.forename: G
authors.initials: G
authors.lastname: Ricci
mesh_terms: D001845:Bone Cysts / Q000000981:diagnostic imaging / Q000209:etiology*; D003937:Diagnosis, Differential; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D010003:Osteoarthritis / Q000150:complications* / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed