How do broken bones heal?

Your body is working hard to repair a broken bone from the moment an injury occurs. See more bodily feat pictures. Brown

If you experience engine trouble, you take your car to a mechanic. If your pipes leak, you call a plumber. And if you fracture a leg, the usual course of action is to visit a doctor. But unlike other things that may break in life, bones begin healing on their own before you even set foot in a waiting room.

The human body possesses amazing healing powers that enable it to bounce back from a vast array of illnesses and injuries. Sometimes broken bones can heal so thoroughly within a few months that even an x-ray can't determine the original fracture line.


Doctors often play a vital, sometimes lifesaving, role in a bone's healing process. But, these experts basically help the body heal itself. Doctors provide optimal conditions for bone repair and healing to take place. The rest is up to your cells.

But how does this amazing biological process work? How can a fractured limb grow back to its former strength? To understand, you first have to take a closer look at just what bones are made of and how alive they really are.


How Broken Bones Repair Themselves

When a bone breaks, your body already has a plan for how to fix it. Sass

It's easy to think of our bones as solid, lifeless matter where all of our living tissue just sits. But your skeleton is as much a living part of your being as your softer tissues and organs. The body stores minerals in the hard, compact bone. It produces red blood cells in the inner red marrow and stores fat in the yellow marrow.

It's important to remember that your bones are constantly changing. Cells called osteoclasts constantly break down old bone so that osteoblasts can replace it with new bone tissue -- a process called bone remodeling. Another type of cell called a chondroblast forms new cartilage. These are three of the primary cells responsible for bone growth -- and not just the bone growth you experience early in life. This constant bone remodeling gradually replaces old bone tissue with new tissue during the course of months.


Almost immediately after the break, the body begins to try and put itself back together again. Doctors often divide the overall process into four phases:

  1. When a bone breaks, the fissure also severs the blood vessels running down the length of the bone. Blood leaks out of these veins and quickly forms a clot called a fracture hematoma. This helps to stabilize the bone and keep both pieces lined up for mending. The clot also cuts off the flow of blood to the jagged bone edges. Without fresh blood, these bone cells quickly die. Swelling and inflammation follow due to the work of cells removing dead and damaged tissue. Tiny blood vessels grow into the fracture hematoma to fuel the healing process.
  2. After several days, the fracture hematoma develops tougher tissue, transforming it into a soft callus. Cells called fibroblasts begin producing fibers of collagen, the major protein in bone and connective tissue. Chondroblasts then begin to produce a type of cartilage called fibrocartilage. This transforms the callus into a tougher fibrocartilaginous callus, which bridges the gap between the two pieces of bone. This callus generally lasts for about three weeks.
  3. Next, osteoblasts move in and produce bone cells, transforming the callus into a bone callus. This hard shell lasts three to four months, and it provides necessary protection and stability for the bone to enter the final stage of healing.
  4. At this point, the body establishes the position of the bone within the flesh, begins reabsorbing bits of dead bone, and creates a hard callus to bridge the gap between the two pieces of bone. However, this bulge of tissue needs a lot of work before the bone can take any strain. Osteoclasts and osteoblasts spend months remodeling bone by replacing the bone callus with harder compact bone. These cells also decrease the callus bulge, gradually returning the bone to its original shape. The bone's blood circulation improves and the influx of bone-strengthening nutrients, such as calcium and phosphorus, strengthen the bone.

But even in the best of cases, fractures often require medical attention to heal as smoothly as possible. Did Humpty Dumpty just need the help of a talented orthopedist? Learn how doctors help broken bones heal properly on the next page.


Medical Treatment for Broken Bones

Two surgeons examine an x-ray of a broken leg.­
Reza Estakhiran/Photographer's Choice/Getty Images

Various complications can occur with fractures depending on the bone, the severity of the break and the person's age. Children are susceptible to additional forms of fractures, but their bones tend to heal faster and more completely than those of adults.

­Infection poses a threat to any compound fracture, as the break in the skin can allow germs to enter. Broken ribs can potentially pierce internal organs, and the healing process itself can inadvertently harm other organs or tissues. In compartment syndrome, a fracture's injured muscle swells so tightly that oxygen can't enter the high-pressure tissue. Without sufficient oxygen, the muscle tissue can continue to swell until injury and muscle death ensue. Pulmonary embolism occurs when a fracture's blood clotting breaks loose and blocks a lung artery. This condition is particularly common with hip and pelvis fractures, accounting for an estimated one-third of hip-fracture deaths [source: The Merck Manuals Online Medical Library Home Edition].


With all of these possibilities in mind, a doctor approaches a suspected fracture by following several steps to ensure the bone heals properly.

  • Diagnosis: The first step involves the doctor determining whether a fracture occurred and, if so, the severity of the injury. The following steps of treatment depend on the physician knowing exactly what he or she is dealing with. Doctors generally accomplish this by examining the patient and inspecting the x-ray of the damaged area.
  • Immobilization: Just as the body does its part to line up broken bones and limit mobility, a doctor must ensure this alignment. He or she further immobilizes the affected area with a splint, cast, brace or sling. Because a fracture may require further alignment, a patient might need anything from a local anesthetic to spinal anesthesia to temporarily lessen the pain.
  • Traction: Simple immobilization isn't always enough to ensure proper bone healing. In the case of more complex factures, a system of weights, ropes and pulleys constantly pull on fractured limbs to maintain alignment.
  • Surgery: Most fractures can be treated without surgery. However, some injuries require doctors to aggressively treat the damaged bone. Sometimes doctors perform surgery to remove foreign materials or bone fragments. The best way to stabilize certain fractures is to go in and align the bones with metal rods, implanted screws and pins. Some fractures, such as those to the hip and joints, require artificial replacements.
  • Rehabilitation: The same immobilization that keeps stress off the healing bone also leaves the surrounding muscles with little to do. This leads to the loss of muscle mass, strength and flexibility. Special exercise regimes allow individuals to gradually rehabilitate their newly healed limbs without risking re-injury.

To learn more about the human skeletal system and how to keep your bones healthy, visit the links on the next page.


Lots More Information

Related HowStuffWorks Articles

More Great Links

  • BoneFixator.Com. "Fractures and Healing." 2007. (April 23, 2008)
  • "Bone Healing." Jan. 29, 2008. (April 23, 2008)
  • The Merck Manuals Online Medical Library. "Fractures." February 2003. (April 23, 2008)
  • Tortora, Gerard J. and Sandra Reynolds Grabowski. "Principles of Anatomy and Physiology, Ninth Edition." John Riley & Sons. 2000.
  • U.S. National Library of Medicine and the National Institutes of Health. "Osteoblast and chrondroblast differentiation." PubMed. Aug. 17, 1995. (April 23, 2008)