When you fracture a bone, the injury sets off a very intricate and lengthy healing process. Bones are tough, but they’re not able to heal from a fracture in a day, a week, or even a month. It takes time and there are steps that must unfold for healing to happen.

One important part of that process is the development of a bone callus, or a fibrocartilaginous callus, at the site of the fracture after the inflammation from the initial injury begins to wane.

This article will take a closer look at bone calluses, how they form and appear, and what you can do to promote healing.

You might wonder why bone calluses form during the bone healing process.

It may help to think about it as a transition: a transition that helps the fractured bone move from the first phase of healing (the inflammatory phase), toward the next phase when the repair work begins.

An illustration of a bone callus, showing how it develops after a bone fracture.  Share on Pinterest
Illustrated by Jason Hoffman

According to the American College of Foot and Ankle Surgeons, there are three phases of fracture healing, which we’ll look at in more detail below.

Inflammatory phase

The inflammatory phase is the first phase of the bone healing process. It begins as soon as the bone is fractured and lasts for several days.

Blood collects at the site of the fracture, causing inflammation and a blood clot to form.

Reparative phase

The second phase of the healing process is the reparative phase, which is sometimes called the bone production phase.

During this phase, a soft, thick callus composed of fibrous tissues and cartilage replaces the blood clot at the fracture site. This callus holds the pieces of fractured bone together, but it’s vulnerable. It’s not strong enough to be used in the way that bone would be used.

The formation of this soft callus occurs somewhere between 2 and 6 weeks after the fracture occurs, according to a 2017 review of bone fracture healing.

Eventually, as healing continues, the soft callus develops into a hard callus. The hard callus is actually bone, but it’s still softer than regular bone.

Bone remodeling phase

Bone remodeling is actually a lifelong process that happens over and over in your body. Old bone tissue is removed and replaced by new bone tissue.

Bone remodeling also happens after a fracture occurs: the callus goes through the remodeling process. Special cells call osteoclasts chip away at the old bone, and other cells called osteoblasts form new bone in its place.

It’s a process that takes many months or even years, and during that time, the bone becomes compact and resumes its original shape.

A bone callus is a normal and temporary development on the road to healing. Ultimately, the callus becomes bone, which hardens and strengthens over time.

The entire healing process can take as long as a year, according to the American Academy of Orthopaedic Surgeons (AAOS). However, the healing timeframe can vary, based on the type and severity of the fracture. And in some cases, the final phase may slowly unfold over the course of a few years.

However, if your doctor is concerned that a bone fracture is not healing properly, or it’s healing more slowly than expected, your doctor may recommend the following to help improve the healing process:

  • immobilizing your fractured bone for a longer period of time
  • trying bone stimulation
  • undergoing surgery with a bone graft or bone growth proteins

After you break a bone, your doctor’s job is to properly align the bone fragments so they can heal correctly. After that, it’s up to you to carefully follow your doctor’s advice and recommendations. It’s also important to avoid activities or behaviors that could slow down the healing process.

You can help promote bone healing by taking the following steps:

  • Follow immobilization instructions: You could inadvertently impede the healing process if you don’t follow the instructions for keeping your broken bone immobilized. If your doctor tells you to stay off a broken leg and not put any weight on it for 6 weeks, it’s important to follow those instructions exactly. If you resume weight-bearing activities too soon on a weakened bone, it could set back your progress.
  • Eat a healthy, balanced diet: Give your body the nutrients it needs to promote healing by eating well. Think lean protein, fruit, and vegetables. Consider including foods rich in vitamin D, calcium, and protein to help with the healing process. Ask your doctor if you need a vitamin D or calcium supplement.
  • Try to stop smoking: Smoking can slow down the healing process. In fact, a 2021 review of multiple studies found that smoking is associated with fractures that don’t heal, as well as deep surgical site infections.
  • Limit or avoid alcohol: Some research suggests that alcohol creates a kind of oxidative stress that can disrupt bone healing.
  • Participate in physical therapy: Your doctor may recommend that you begin physical therapy at some point. These sessions can help you regain your strength and range of motion. Physical therapy can also help you learn how to adapt your movements and move safely so you don’t re-injure yourself or put unnecessary stress on a healing fracture.

Recovering from a bone fracture takes time and patience. One important part of the healing process is the development of a bone callus. It develops at the site of the fracture, around 2 to 6 weeks after the bone is broken.

A bone callus first starts off as soft fibrous tissue and cartilage. As healing continues, the callus becomes bone, which hardens and strengthens over time.

The entire healing process for a bone fracture can take as long as a year, but depending on the severity and type of fracture it can take longer.