Structure is considered to be the base of the triangle. Structure deals not only with obvious factors such as slipping and twisting of joints and muscles but also deals with structural instability and consequent joint involvement such as osteoarthritis, joint strains and irritation of the nerve roots as they exit the spinal canal.
Direct trauma is often what brings a patient to a doctor specializing in structure. If the problem is an acute trauma, such as a lifting injury or a fall, which has affected the various joints and muscles of the body it can be corrected via the appropriate structural treatment.
However, it is important to note that many times a person's chief complaint may appears to be structural in nature but it can actually originate from the other sides of the triad, nutrition/chemical and/or emotional/spiritual.