The ‘knee’ pattern in spirometry flow-volume curves in children: Does it relate to tracheomalacia?

•In this study, we found that the ‘knee’ in spirometry flow-volume curves was often associated with an airway condition in children.•Tracheomalacia diagnosed by flexible bronchoscopy was found in 65% of children with the ‘knee’ pattern.•A scoop before plateau of the ‘knee’ was significantly associated with tracheomalacia diagnosed by flexible bronchoscopy.