Two days ago, I fell hard while running up some steps and hurt my wrist. I was told I might have a hairline fracture of my wrist, but no x-rays were done and I didn't get a cast. What exactly is a hairline fracture, and what's the difference between a fracture and a broken bone? - Kelly

The medical term for any break in a bone is a fracture. There are hundreds of terms to describe fractures and their locations, but a few of the more important ones for patients to know are open, displaced, and non-displaced.

Open fractures are where a bit of jagged broken bone has poked through the skin. They can be prone to infection, and often require a surgical washout and repair.

Displaced fractures are where the cracked edges of broken bone don't line up. The more severe ones will need to be pushed into alignment. They will need a cast, and some may need surgery with plates and screws to hold the bones in alignment.

Non-displaced fractures are where a crack occurs, but everything still lines up normally. Hairline fractures are a type of non-displaced fracture. On an x-ray, the bone can appear to have an extremely thin crack in it. But many times nothing abnormal shows up on the initial x-ray. The patient may have pain and tenderness, but the first x-ray may be perfectly normal.

If the pain persists, getting a repeat x-ray in seven-10 days usually shows a hairline fracture. The initially invisible line becomes visible as the body heals itself, absorbing damaged bone at the fracture site. By 14 days, a whiter line (the new bone) is visible.

Sometimes doctors feel that the chance of a "real" fracture is so low that they don't get an x-ray but just choose to wait and see. Most hairline fractures will heal fine with minimal treatment, so some doctors may just place a splint and see how it goes.

There are a few exceptions; hairline fractures in some bones, like the tiny scaphoid bone in the wrist, often heal badly, and need a special cast. Stress fractures of the weight-bearing bones of the leg or foot, may be prone to recurrence and may need more of a plan than just wait-and-see. But in general, hairline fractures most often do come right.