How Does a Broken Bone Heal? Stages of Fracture Healing and What Speeds It Up
How does a broken bone repair itself? Clot, callus and remodelling stages, healing times and causes of delayed union.
Short answer: Bone is one of the few tissues that can repair itself without leaving a scar. After a fracture a blood clot forms first, then a soft bridge (soft callus) is built, this bridge hardens with minerals into bone (hard callus), and finally the bone remodels back to its original shape over months to years. Healing time depends on the bone, age and general health: finger and wrist fractures usually take 4 to 8 weeks, and weight-bearing bones such as the shin may take 3 to 6 months. Children usually heal faster.
Dr Ahmet Şadi Kılınç, Orthopaedics and Traumatology Specialist, Bahçeşehir, Istanbul
The question patients with a fracture ask most is: “When will it heal, when can I walk, when can I return to sport?” The answers depend on understanding how bone heals. In this article I explain the stages of repair, healing times and the factors that affect them.
I also explain it in a short video, in Turkish: watch on YouTube.
The four stages of fracture healing
1. Clot and inflammation (first days to 1 week). When the bone breaks, bleeding between the broken ends forms a clot (haematoma). This clot sends the chemical signals that call repair cells to the site. Pain, swelling and bruising are normal at this stage.
2. Soft callus (about weeks 1 to 3). The clot is replaced by a soft bridge of cartilage and connective tissue. The ends are now joined but not yet strong, so the fracture must be protected.
3. Hard callus (about weeks 3 to 12). The soft bridge hardens with calcium and other minerals into bone. On X-ray, new bone called callus appears around the fracture. The bone gradually becomes able to bear load.
4. Remodelling (months to years). Extra bone is reshaped and the bone returns towards its original shape and thickness. In children this stage is very effective; small angulations can correct over time.
How long does it take?
Time depends on the site, type of fracture and the person. As a general guide:
- Fingers and hand bones: about 4 to 6 weeks
- Wrist (distal radius): about 6 to 8 weeks
- Collarbone: about 6 to 12 weeks
- Shin bone (tibia): about 3 to 6 months
- Thigh bone (femur): about 3 to 6 months or more
- Children: usually shorter than adults for the same fracture
These are approximate; the time to put weight on the limb should always be set by your treating doctor from the X-ray.
What speeds healing and what slows it
Speeds it:
- Correct alignment and enough fixation (cast, splint, plate and screws, nail and so on)
- Enough protein, calcium and vitamin D
- Loading and attending check-ups as your doctor advises
- A preserved blood supply to the fracture
Slows it:
- Smoking. It clearly delays bone healing and increases the risk of non-union.
- Poorly controlled diabetes
- Vitamin D deficiency and poor nutrition
- Infection
- Movement at the fracture (poor fixation)
- Older age and osteoporosis
- Severe injuries that damage the blood supply
- Some medicines (for example long-term cortisone)
Nutrition while a fracture heals
- Enough protein at every meal (meat, fish, eggs, dairy, pulses)
- Calcium sources (milk, yoghurt, cheese, green leafy vegetables)
- Vitamin D supplements if low, as advised by your doctor
- Enough fluids and a variety of vegetables and fruit
For the general building blocks of bone health, read our bone health article.
What if the fracture does not heal?
Some fractures do not heal in the expected time (delayed union) or at all (non-union, pseudarthrosis). Ongoing pain and movement at the fracture and no callus on X-ray suggest this. Often it is solved once the cause is found and corrected, for example by strengthening the fixation or adding bone graft.
When to see a doctor straight away
- Increasing, unbearable pain under a cast or splint
- Blue, cold or numb fingers or toes, or inability to move them
- Fever or discharge from the wound
- Calf pain and swelling in the leg after a fracture (clot risk)
- New deformity or suddenly worse pain at the fracture
For more about our fracture care, see Fracture and Dislocation Treatment or book an appointment. If you wonder why a cast is kept long, read why a wrist fracture cast reaches the elbow.
This article is for general information and does not replace an examination.
Frequently asked questions
How does a broken bone heal?
A clot forms at the fracture, then a soft bridge is built, it hardens with minerals into bone, and over months the bone remodels to its original shape.
How long does a broken bone take to heal?
It varies with the site and the person. Hand and finger fractures take about 4 to 8 weeks; weight-bearing bones such as the shin may take 3 to 6 months. Children usually heal faster.
What speeds up fracture healing?
Correct alignment and fixation, enough protein, calcium and vitamin D, loading as your doctor advises, and not smoking.
Does smoking affect fracture healing?
Yes. Smoking delays bone healing and increases the risk of non-union.
How do I know if a fracture has not healed?
If pain and movement continue beyond the expected time and the X-ray shows no callus. Depending on the cause, fixation can be strengthened or bone graft used.
The information on this page is general and does not replace an examination. An examination is needed to decide which treatment suits you.