The coccyx is the most terminal bone of the spine, and its alignment is such that it connects to the sacrum above and slowly bends to the posterior side in a curved hook-like fashion below. The coccyx differs from the other vertebrae of the spine in that there is no arch or canal. The lower end of the coccyx is a point and the upper end is the base, while the oval articular surface of the base of the coccyx can form a joint with the sacral point, and the depression above the posterior part of the coccyx can form the sacrococcygeal space with the connected part of the sacrum. The posterior edge of the base of the coccyx is higher than the anterior edge but is oriented downward, with the anterior edge slightly concave and smooth and the posterior edge prominent and rough. The shape of the coccyx is affected by the pulling of the surrounding muscles, ligaments, and other soft tissues, so the shape of the coccyx is variable, and there can be asymmetry between the two sides, as well as forward bending of the curvature of the coccyx.