A deviated septum is a condition in which the nasal septum — the bone and cartilage that divide the nasal cavity of the nose in half — is significantly off center, or crooked, making breathing difficult. Most people have some sort of imbalance in the size of their breathing passages. In fact, estimates indicate that 80% of people, most unknowingly, have some sort of misalignment to their nasal septum. Only the more severe imbalances cause significant breathing problems and require treatment.Some people are born with a deviated septum. Other people develop a deviated septum after injury or trauma to the nose.