In as many as 80% of cases, doctors don’t find the exact reason for a curved spine. Scoliosis without a known cause is what doctors call “idiopathic.”
Some kinds of scoliosis do have clear causes. Doctors divide those curves into two types -- structural and nonstructural.
In nonstructural scoliosis, the spine works normally, but looks curved. Why does this happen? There are a number of reasons, such as one leg’s being longer than the other, muscle spasms, and inflammations like appendicitis. When these problems are treated, this type of scoliosis often goes away.