Flat bone
Also called: flat bones
What it means
A flat bone is a thin, broad, often curved bone—like the skull, ribs, sternum, or pelvis—built from a layer of spongy bone between two layers of dense bone.
Flat bones like the pelvis and ribs are common fracture sites and contain marrow, so their shape and structure matter for overall skeletal and blood health.
Flat bones are one of the basic shapes of bone found in the skeleton, alongside long bones, short bones, and sesamoid bones. Rather than being long and cylindrical like the femur, flat bones are thin, broad, and usually curved. Common examples include the skull bones, sternum, ribs, scapula, and parts of the pelvis like the ilium.
Structurally, flat bones are made of a layer of spongy trabecular bone sandwiched between two layers of denser cortical bone, sometimes called a 'sandwich' design. This gives them strength while keeping them relatively lightweight. Many flat bones, like the sternum and pelvis, also contain red bone marrow, which is important for making blood cells.
For bone health, flat bones matter mainly because sites like the pelvis and ribs can be affected by fragility fractures, and because marrow-containing flat bones are sometimes involved in conditions like multiple myeloma or bone metastases. Understanding bone shape helps explain why different bones respond differently to loading and disease.
Flat bones like the pelvis and ribs combine spongy and dense layers, and they're common fracture and marrow sites.
Where this leads
WordThe pelvis is one of the flat bones you just read about. Curious why keeping this weight-bearing bone strong matters so much.
Related words
A long bone is a bone that's longer than it is wide, like the femur or humerus, with a shaft and two ends. These…
A short bone is a roughly cube-shaped bone, like those in the wrist and ankle, that's about as wide as it is long.
A sesamoid bone is a small bone embedded inside a tendon, usually near a joint, that helps reduce friction and…
Trabecular bone is the spongy, honeycomb-like bone found inside structures like your spine and hip, providing…
Cortical bone is the dense, hard outer layer of bone that forms a protective shell and resists bending and twisting…
The pelvis is the large, bowl-shaped bone structure that connects your spine to your legs and supports your body weight.
Education only, not medical advice. Decisions about tests, medications and treatment belong with your own doctor. OsteoStrong does not diagnose, treat or cure any disease.
