Bone Healing (Fracture Healing)

Bones are strong, but they can break, or “fracture,” if hit hard enough or put under too much stress. When a bone breaks, the body immediately begins a natural healing process to fix the damage. Bone healing is important to get back to normal movement and function. Healing happens in three main stages: the inflammatory phase, the reparative phase, and the remodeling phase (Figure 1). Each stage plays a key role in helping the bone recover and become strong again.

Bone Healing Phase 1: Inflammatory Phase

The first stage is the inflammatory phase, which starts right after the bone breaks. Blood vessels within the bone are damaged at the time of the fracture, which causes bleeding and swelling around the fracture site. The body sends special cells to clean up the area and begin the healing process. These cells remove damaged tissue and prepare the bone for repair. This inflammatory phase usually lasts a few days to a week. The fracture site will be painful and swollen, but it’s a sign the body is starting to heal.

Bone Healing Phase 2: Reparative Phase

Next comes the reparative phase, which usually starts around a week or two after the injury. During this time, the body starts building new bone. First, a soft callus made of collagen forms around the break. Then, over several weeks, this soft callus is slowly replaced with a hard callus made of bone. This helps stabilize the fracture and keep the bone together. This reparative phase can last several weeks to a few months, depending on the injury and the person’s health.

Bone Healing Phase 3: Remodeling Phase

The final stage is the remodeling phase. This phase begins as soon as the hard callus forms and typically lasts months to years. In this remodeling phase, the body reshapes the bone to make it look and work like it did before the break. It removes extra bone and strengthens the healed area. Over time, the bone becomes just as strong as it was before the injury, or sometimes even stronger.

Nonunion: Failure of a Bone to Heal

Sometimes, bone healing doesn’t go as planned. A nonunion is when a broken bone or an attempted joint fusion fails to heal properly or doesn’t heal at all. Several things can increase the risk of a nonunion. These include smoking, which reduces blood flow, vitamin D deficiency, poor nutrition, and too much movement at the fracture site. Medical conditions like diabetes can also slow down healing.

Bone Healing in Joint Fusions

In some joints that have severe arthritis treatment may involve fusing the arthritis joint. Joint fusion commonly is done to treat ankle, midfoot, great toe, and many other joints affected by severe arthritis. A joint fusion aims to create a solid bony fusion across the joint, thereby eliminating the pain from arthritis. The bone healing process that occurs in a joint fusion is identical to that seen in fracture healing. Similarly, a known complication of an attempted joint fusion is a nonunion.

Stimulating Bone Healing

Certain actions can help bones heal better. Immobilizing the bone with a cast, brace, or surgery helps keep it stable which can improve bone healing. A healthy diet that includes calcium and vitamin D is also important. Getting enough rest and following the doctor’s advice are also key steps to help the bone healing go well. In situations where a nonunion has previous occurred, or the bone healing is expected to be difficult electrical stimulation may be used to encourage healing. Running a small electrical current through the fracture site has been shown to induce the bone forming cells (osteoblasts) to divide and grow, ultimately producing more new bone.

The Importance of Rehabilitation following a Fracture

When a bone breaks, it’s not just the bone that suffers. Muscles nearby will often weaken (atrophy) from not being used. Nearby joints may get stiff and lose their range of motion. Nerves can also be affected, especially those that help with proprioception—the sense of body position and movement. For these reasons rehabilitation following a fracture is essential. A rehabilitation program usually includes exercises to regain strength, flexibility, and balance.

In summary, bone healing is an amazing natural process that happens in three stages: inflammation, repair, and remodeling. Most bones heal well with the right care, but some may need extra help. A healthy lifestyle and proper treatment give bones the best chance to heal strong. And remember—healing isn’t just about the bone; the whole body needs to recover!

Edited by Stephen Pinney MD, April 20th 2025