Infrasternal Angle
Definition
The angle formed by the left and right costal margins where they meet at the xiphoid process. Normal infrasternal angle is approximately 80-90 degrees. A wide infrasternal angle (greater than 90 degrees) indicates rib cage external rotation (flare). A narrow angle (less than 80 degrees) indicates rib cage depression.
Clinical Significance
The infrasternal angle is one of the fastest clinical indicators of rib cage position and respiratory mechanics. A wide angle is associated with extension-based postures, anterior pelvic tilt, and loss of the zone of apposition. A narrow angle is associated with flexion-based postures and thoracic kyphosis. The angle determines whether the primary intervention should be rib cage depression (wide) or rib cage expansion (narrow).
How AKMI Assesses This
AKMI measures the infrasternal angle through direct observation and photographic analysis in standing. The measurement is correlated with pelvic tilt, thoracic kyphosis, and breathing pattern findings to determine the rib cage contribution to the overall structural presentation.
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