Callus (bone)
Also called: fracture callus, bony callus
What it means
A bone callus is the new tissue, soft at first and then hardened, that forms around a fracture to join the broken bone ends back together.
Knowing how a callus forms helps you understand why fractures take weeks to heal and why your doctor checks healing before you return to full activity.
A bone callus is the tissue your body builds to bridge and repair a fracture. After a break, the periosteum (the tissue covering the outside of bone) and nearby cells rush in to form a soft, then hardening, bridge of new tissue around and between the broken ends. Over weeks, this soft callus gradually mineralizes into a firmer, bony callus that stabilizes the fracture.
This process is a natural part of fracture healing stages: inflammation, soft callus formation, hard (bony) callus formation, and finally remodeling, where the extra bony bulge is gradually reshaped and smoothed down closer to the bone's original contour. The periosteum is especially important here, since it's the main source of the cells that build new bone during this repair.
Understanding callus formation helps explain why healing takes time and why follow-up X-rays are used to confirm bone union before resuming full weight-bearing or activity. If a callus doesn't form properly, it can lead to delayed union, nonunion, or malunion, which your doctor may monitor or treat differently depending on the fracture.
How sure is this?
Graded Established Science: Supported by broad scientific consensus and decades of research. Read each study with its grade in mind. One study is a piece of the picture, not the whole of it.
A soft-to-hard callus rebuilds the fracture site, which is why healing and return to activity take weeks.
Where this leads
WordCurious what happens before and after the callus forms? See the full staged process your bone follows to heal.
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
Fracture healing is the body's natural, staged process of repairing a broken bone, moving from initial bleeding and…
The periosteum is the thin membrane that covers the outside of your bones, carrying blood vessels and nerves into…
Bone union means a broken bone has fully healed and the two ends have knit back together with new bone, restoring…
A nonunion is a broken bone that has stopped healing and won't knit back together on its own, even months after the…
A malunion is a broken bone that healed, but in a crooked, shortened, or misaligned position instead of its normal…
Delayed union is when a fracture takes longer than usual to heal, though it's still making progress toward healing.
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.
