While correction of a crooked nose may often require both a septoplasty & rhinoplasty, this is not always the case. Sometimes, for example, after a relatively recent fracture of the nasal bones (within the last several years), it will be a bony deformity that causes the crookedness rather than any deviation of the nasal septum on the inside. In this case, a rhinoplasty will be required instead of a septoplasty to straighten the crooked nasal bones.
Commonly in more long-standing nasal deformities, the cartilage of the nasal septum is also involved. A nasal septum problem may be identified in one of two ways. One, deviation of the nasal septum inside the nasal airway often contributes to nasal airway obstruction. While this obstruction, which causes difficulty breathing, may be on both sides of the nose, a deviated septum will often produce obstruction on one side only. Hence, nasal airway obstruction would be a very good indicator of the need for a septoplasty as well as a rhinoplasty to straighten a crooked nose.
Secondly, if the crookedness is closer to the tip of the nose, by looking in a mirror you can often quite easily see the crookedness of the cartilaginous divider in the middle of the nose, contributing to that crookedness. In this case, a septoplasty will certainly need to be combined with a rhinoplasty to correct the problem. A septoplasty alone, however, will rarely correct a crooked nose all by itself.