What is “Force Closure”?

In case the concept of Force Closure still seems illusive this picture and brief explanation should elucidate further.

The lumbodorsal fascia (LF) forms a mechanical link between the gluteus maximus (GM) on one side and the latissimus dorsi on the other. The force transmitted across the pelvis will act to press the surfaces of the left-hand side SIJ closer together. In this way, the bilateral effects of this linkage may be to stabilize the SIJs by the mechanism of ‘Force Closure’.

The action of muscle-contraction generating force vectors link the bony surfaces into contiguous, single motion entities capable of the enormous loads the human frame is capable of lifting.

We ‘supplement’ “Form Closure” (the unique bony shapes of the surfaces) via external-bracing or compression as a therapeutic device to judge the extent an impaired motion is not directly compression on a disc. Adding contraction/bracing; Force Closure further demonstrates the non-compression aspect of the problem and the likelihood stabilization via exercise will result in improved motion.