If something interferes with the capacity of either facet to close normally, restriction of backward bending will occur. For example, if a right facet does not close normally, but the left does close normally, left sidebending will be possible but right sidebending will be restricted in the backward bent position. In the cervical spine during flexion/extension, sidebending and rotation are coupled movements in the same direction. Therefore, rotation will also be affected by facet joint dysfunction. If the right facet does not close normally, we would expect to encounter abnormal resistance with right to left translation in the backward bent position. The segment is said to be restricted in extension, rotation right, and sidebending right. The positional diagnosis is FRSleft, and the motion restriction is ERSright.
For example, while monitoring a typical cervical segment at the articular pillars, you extend the cervical segment by gently lifting it. You notice that the finger you have placed upon the left articular pillar moves slightly inferior and posterior, but the finger monitoring the right articular pillar does not move (or if it does move, it moves less than the left side). You also notice that you encounter abnormal resistance when you translate the segment from right to left. When you flex the patients cervical spine, you note that both fingers monitoring the articular pillars move symmetrically, slightly anterior and superior, and that you encounter normal translational resistance in both directions. We know that in flexion the facets are supposed to open, and that in extension the facets are supposed to close.