Bone healing or fracture healing is the process by which your body repairs a fracture. The healing process is very complex and depends on the coordinated interactions of many biologic events in your body. But we will try to cover everything you need to know about the process of bone healing in this article.

You should know that bones heal in one of two different ways. The first way is called primary or direct healing, which is further classified as either contact healing or gap healing. Primary bone healing requires complete immobilization throughout the repair process. The far more common, second way is called secondary or indirect healing. Since this is the most common process by which most fractured bones heal, the rest of this article will describe the complex process of indirect fracture healing.1,2

Four stages of indirect bone healing
The indirect bone healing process consists of four main phases:

  1. Acute inflammatory response
  2. Production of a soft callus
  3. Production of a hard callus
  4. Bone remodeling

The acute inflammatory phase
The acute inflammatory phase is the first stage in the process of indirect bone healing. This phase occurs immediately after you incur the injury that led to the bone fracture. The fracture triggers a brief inflammatory response, which is critical for the regeneration of healthy bone tissue. Cells that have the ability to differentiate into new bone cells, called mesenchymal stem cells, begin to move to the site of the bone fracture during the acute inflammatory phase. About 48 hours after the injury that caused the bone fracture, blood vessels that were torn by the fracture release blood at the ends of the broken bone and form a clot, called a fracture hematoma. The clot may disrupt blood flow to the bone, causing some bone cells around the fracture to die. The acute inflammatory phase lasts approximately one week.

Production of a soft callus
The initial production of new bone tissue begins a few days after you experience a fracture. It starts when the clotted blood, formed during the acute inflammatory phase, is replaced with fibrous tissue and cartilage. This tissue, also known as a soft callus, is formed in between the two ends of the broken bone.1,3 This phase lasts about 2 weeks.4

Production of a hard callus
The next phase begins with the resorption of the soft callus tissue, which is replaced with hard callus tissue, also called a bony callus. The lattice structure of the newly formed bone is also called spongy bone or trabecular bone. Calcium is deposited in this new bone lattice in a process called ossification. The hard callus continues to grow, bridging the gap in the broken bone, until the two ends meet. The function of the hard callus is to stabilize the fracture by adding a rigid structure and strength. The hard callus phase may last between 4 and 16 weeks.1,3,4

Bone remodeling phase
The remodeling phase is the final stage in the process of indirect bone healing. At this stage, solid bone replaces the spongy bone created during the hard callus phase. This replacement of trabecular bone with solid, lamellar bone takes about 3 to 4 weeks. However, completion of the remodeling phase may take months to years, depending on the health status of the patient and the presence of any fracture complications.1,4

Healing time
Now that we know what happens during the overall process of indirect bone healing, let’s talk about healing time. A broken bone may heal in as little as 6 to 8 weeks or take months to fully heal. In general, children’s bones tend to heal faster than those of adults. The good news is most people stop feeling pain long before the process of bone healing is fully completed. However, your treating physician will let you know when your healed bone is ready for regular activity, and when you may put your body weight on the area, if the broken bone was in one of your limbs.3,4

Variables that influence the bone healing process
The bone healing process is not the same for everyone. There are many variables that may increase the time it takes for your broken bone to heal.

Patient factors that may prolong the healing time include:

  • Older age
  • Chronic conditions that impair blood flow to the fracture site, such as diabetes or hypertension
  • Use of medications that suppress the inflammatory response, such as nonsteroidal anti-inflammatory drugs (NSAIDs) or corticosteroids
  • Poor nutrition
  • Tobacco smoking, which may impair blood flow

Broken bone factors that may prolong the healing time include:

  • The type of fracture (open versus closed)
  • The extent of the trauma (multiple traumatic injuries)
  • Presence of complications, such as infection at the site of the fracture

Any of these factors may increase the risk for prolonged healing, called a delayed union, or for a failure of the bone to heal, called a nonunion.4

Try EXOGEN if you want to speed up the healing process
EXOGEN is an FDA-approved device that helps to speed up the process of bone healing in just 20 minutes a day. It takes place in your home, and at your convenience. With EXOGEN, you get a safe, painless treatment that amplifies your natural bone-healing power. This facilitates faster healing of certain broken bones,* and restores healing to fractures that have failed to heal on their own.

Just make sure you use the simple-to-operate device on a daily basis. This is essential for EXOGEN to work. The internal usage monitor automatically records each treatment, so you can track your daily progress.

Read more about how EXOGEN´s bone stimulator works here, and find out if it’s right for you!


  1. Sousa CP, Dias IR, Lopez-Pena M, et al.  Bone turnover markers for early detection of fracture healing disturbances: A review of the scientific literature. An Acad Bras Cienc.2015;87(2):1049-61.  doi: 10.1590/0001-3765201520150008.
  2. Fractures (broken bones). Last updated: October 2012.
  3. Silva JC. What to know about bone fracture repair. Last updated July 10, 2018.
  4. Brazier Y. (2019). What is a fracture? Last updated December 14, 2017.
  5. NYU Langone Health. Diagnosing nonhealing fractures. Accessed 7 Oct. 2019.