What's the difference between a "stress reaction" and a "stress fracture"? The orthopedic surgeon is trying to decide if I have a stress reaction of the navicular bone in my left foot.

Let's look at what's the same about these two problems. The key thing they have in common is that the injury occurs in response to repetitive overloading of the bone. This is most common in athletes involved in sports activity. Long-distance runners, military recruits, track and field athletes, and gymnasts are the most likely to suffer a navicular fracture.

The navicular bone is located in the midfoot. The tarsal bone rests on top of the calcaneal (heel) bone. The navicular bone is just in front of the tarsal bone on the same side as the big toe.

The difference between a 'reaction' and 'fracture' is a matter of degree. Both suggest a disruption of the bone metabolism. Fracture can be seen on most imaging studies (X-ray, MRI, CT scan), whereas a stress reaction only shows up as increased bone activity on a bone scan.

Both injuries cause midfoot pain and swelling. Weight-bearing (walking, running) make it worse; resting makes it better. Both should be treated with six weeks of casting with nonweightbearing.