Wolff’s Law states that bone grows and remodels in response to the forces that are placed upon it in a healthy person. After an injury to a bone, placing specific stress in specific directions to the bone can help it remodel and become normal, healthy bone again. Your physical therapist should understand Wolff's law to help guide your rehabilitation after a fracture or broken bone.
How Wolff's Law Applies to Physical Therapy
Wolff’s Law applies to physical therapy in the treatment of osteoporosis and after a fracture. If you have osteoporosis, your bones may be brittle and weak. This can lead to pathologic fracture, most commonly in the spine or hip.
Weight-bearing and strength exercises are usually recommended as a non-medicinal treatment for osteoporosis. Putting gradual and progressive weight through a bone can help it grow into healthy bone.
If you have suffered a fracture, bone healing occurs while you have been immobilized with a cast or splint. After immobilization, a gentle range of motion and stress can help improve the overall strength of your bone. This can help ensure that your bone is able to tolerate the loads and stresses that you may encounter during normal functional activities.
How Necessary Stress Is Safely Applied to Bones in PT
In physical therapy, the single best way to increase stress through your bones is through exercise. But after a fracture, your bones may not be able to tolerate vigorous exercise; too much stress during the healing process can actually re-injure your broken bone. That is why you typically wear a cast or brace after a fracture. You must protect your fractured bone as it heals.
But what if you have been immobilized in a cast or sling after a fracture? How can you safely start applying the right stress to your injured bone to promote optimal healing? That's where the skilled services of your physical therapist come in.
Your PT can help guide you by prescribing the right exercises for you to do that will add gradual and progressive stress to your injured bone. For example, after an ankle fracture, your doctor may order that you remain non-weight bearing for a few weeks immediately after the injury. During this time, there may be some benefit of early mobilization for your ankle. Your physical therapist can prescribe safe exercises that you can do that will place gentle stress on your bone while helping you maintain mobility.
Once some healing has taken place after your fracture, your PT can help progress that amount of stress through your healing bone. He or she can prescribe partial weight-bearing exercises and help you progress them to full weight-bearing exercises. By controlling this progression, your PT can ensure that you safely return to optimal function quickly and safely.
Specific Stress Equals Specific Adaptations to Bones
The SAID principle is one that comes into play here. SAID is an acronym for specific adaptations to implied demands. That means that your body will adapt to the demands that you place upon it every day.
If you practice rowing, the muscles and joints specific to rowing will be worked regularly, and they will adapt to help you become a better rower. In the case of bone remodeling, specific loads to the injured bone will help it adapt to tolerate futures loads and stresses. This is the basis for Wolff's Law.
Although your physical therapist may not talk with you about Wolff's Law, the basic tenets of the law help guide your rehab.
Your physical therapist can help you with strategies to start applying stress to your bone after injury and fracture or if you have osteoporosis. This can ensure that proper healing takes place and that you return to normal function quickly and safely.
A Word From Verywell
A broken bone can be a painful and scary experience. It may leave you feeling like basic functional tasks are difficult. Your physical therapist is an expert in helping you regain mobility after a fracture. One important rule to follow during your rehab is Wolff's Law: bones grow and remodel in response to the stress you put on them. A well-rounded PT and rehab program can ensure you get back to your normal lifestyle quickly and safely.