Coccyx Location
The coccyx (tailbone) is located at the terminal caudal end of the spine, below the sacrum and above the anus, positioned in the midline of the body. 1, 2
Anatomical Position and Relationships
The coccyx occupies a specific anatomical position with several key relationships:
Craniocaudal position: The coccyx sits immediately inferior to the sacrum, representing the most distal segment of the vertebral column 3, 1
Relationship to gluteal anatomy: The coccyx lies below an imaginary line connecting the tops of the two gluteal cleft forks, positioned at the base of the gluteal cleft 4, 5
Surface anatomy: In the seated position, the coccyx forms one leg of a weight-bearing tripod along with the two ischial tuberosities, supporting body weight during sitting 1
Pelvic location: The coccyx is situated in the midline perineal region, with pain in this area typically localized below the sacrum and above the anus 2
Developmental Context
Understanding coccyx location requires knowledge of spinal development:
Embryological formation: The coccyx and structures below S2 are formed through secondary neurulation from the caudal cell mass, occurring beneath fully formed skin 6
Spinal cord relationship: While the spinal cord extends from cervical through S2 levels, the coccyx itself lies below the termination of the spinal cord 6
Clinical Significance of Location
The coccyx's anatomical position has important clinical implications:
Distinguishing normal from pathologic findings: Dimples or tracts located at or below the line connecting the tops of the gluteal cleft forks (on the coccyx) are innocent and require no imaging, while those located cranial to this line on the flat part of the sacrum are pathologic and require surgical evaluation 4, 5
Functional anatomy: The coccyx serves as an insertion site for multiple muscles, ligaments, and tendons, making its location critical for pelvic floor function 1