Force Closure: An increase in joint stability via compressive forces resulting from muscular contraction and increased tension in fascial structures (1, 2). This term is most often used in reference to core intrinsic stabilizers, the thoracolumbar fascia, and the sacroiliac joint. For example, the stability of the sacroiliac joint is due to the muscles supporting it (force closure), and the shape of the sacrum and ilium (form closure)