Table 4 Joint motion surplus to end-range in quartiles. The quartiles of pro-directional surplus flexion and extension motion for joints C0/C1 to C6/C7. The motions were divided into quartiles of end-range motion, with the smallest end-range motion in quartile 1 and the largest end-range motion in quartile 4. Each quartile shows the pro-directional surplus motion in degrees and as a percentage of the associated end-range motion. The first column from the left shows quartiles, the second column shows motion direction, degrees and percentages and the next seven columns show joints C0/C1, C1/C2, C2/C3, C3/C4, C4/C5, C5/C6 and C6/C7, the last two columns show upper cervical joints C0/C3 and lower cervical joints C3/C7. The table is divided in two, with the upper half showing flexion motion and a lower half showing extension motion. The number of joints in each quartile is given in the bottom row of each half. The calculations for flexion of C5/C6 and C6/C7 included only 8 and 5 joints respectively. The smallest number of joint observations in the extension table was eight, seen at C0/C1

From: The global end-ranges of neck flexion and extension do not represent the maximum rotational ranges of the cervical intervertebral joints in healthy adults - an observational study