Curiosity Challenge: How Do Bones Heal When They Break?

By Paola Salazar

So, how do bones heal when they break? I’m actually super excited you asked! Bone healing is very fascinating stuff.

When you break a bone, as soon as it happens, your body starts working up a storm to fix it. The first in the line of duty is your blood: it begins to cluster around the location of the break and forms a blood clot, where cells called phagocytes then begin cleaning the area of any unwanted bacteria and germs that may have gotten in through the break and injury. This all happens in the first few hours after the injury.

After a few days or 2-3 weeks, a soft callus made by cells known as chondroblasts forms around the site of injury. Towards the end of the 2^nd week, a harder callus gets formed by osteoblasts, cells that actually create new bone material.

The last team of bone experts to hit the scene comes in at around the 5^th or 6^th week. These are the osteoclasts, which are cells that focus on remodeling the bone around the fracture by breaking down excess bone until the site has been weaned back to its original shape. These guys are perfectionists though, and this stage can sometimes take even more than a decade!

An osteoclast working its way across bone! PC: PathologyOutlines.com

The timeliness of when your bone heals varies so much because when you get an injury like a bone fracture, how quickly you heal depends on several factors—namely, how old you are and where exactly you broke your bone.

The younger you are, the more quickly your body is able to fix you up. As you get older, it takes longer, because your body is getting slower and slower at producing the materials needed for wound healing, while the osteoclasts (the perfectionists), are sometimes still removing bone.

Where you break your bone also matters because it can influence the type of bone fracture that you have—and obviously, the simpler the break, the faster it heals!

Paola is a Boston-based science journalist with a background in social and life sciences.