In medical terminology, what is a geode most accurately described as?

• A. A subchondral cyst
• B. A soft tissue cyst adjacent to joint
• C. A fracture fragment within bone
• D. A fluid-filled cavity in the bone marrow

Answer: (A)

A geode is a subchondral cyst—a cavity in the bone just beneath the articular cartilage of a joint. It forms when joint degeneration allows synovial fluid to seep through cartilage fissures into the subchondral bone, creating a fluid-filled space that’s often lined by fibrous tissue. On imaging, you’d see a radiolucent area directly under the joint surface. This distinguishes it from soft tissue cysts that sit outside the bone near the joint, from fracture fragments that are pieces of bone, and from cavities within the bone marrow, which are not located directly beneath the cartilage. So the defining description is a subchondral cyst.