Endosteum
Also called: endosteal surface
What it means
The endosteum is the thin layer of cells lining the inner surface of bone, next to the marrow cavity.
This is where a lot of age-related inner bone thinning happens, which can weaken bone even if its outer width looks normal on a scan.
The endosteum is a thin layer of cells that lines the inside of your bones, facing the hollow marrow cavity. It's the mirror image of the periosteum, which covers the outer surface of bone. Both layers contain cells that can build or break down bone, but they tend to behave differently depending on your age and what's happening in your body.
As people get older, the endosteal surface tends to become the main site of bone loss. Cells there remove bone from the inner wall of the cortex, a process called endocortical resorption, which can make the bone's outer shell thinner over time even as the overall width of the bone may stay the same or increase slightly.
This matters because a standard DEXA scan measures bone density as a flat, two-dimensional picture and can't separate what's happening at the endosteum from what's happening at the periosteum. So two people with similar-looking scan results might have very different patterns of bone change happening on the inside versus the outside of the bone.
Inner bone thinning often starts at the endosteum, weakening bone even if outer width looks normal.
Where this leads
WordEndosteum sits right next to the marrow cavity. See how changes in this hollow space affect overall bone strength as you age.
Where the Academy teaches it
This page is the short version. The lessons teach it in full, with the context around it and a quiz to lock it in.
Related words
The periosteum is the thin membrane that covers the outside of your bones, carrying blood vessels and nerves into…
Cortical bone is the dense, hard outer layer of bone that forms a protective shell and resists bending and twisting…
Endosteal resorption is the thinning of bone from the inner surface outward, which widens the hollow space inside…
Bone remodeling is the lifelong cycle where cells called osteoclasts remove old bone and osteoblasts build new bone…
A DEXA scan is a low-radiation X-ray test that measures how much mineral is in your hip and spine bones, giving you…
The marrow cavity is the hollow, central space inside a long bone that holds bone marrow.
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.
