The sacral area forms a fundamental part of the lower back and pelvis, acting as a central connection point in the human skeletal system. This region, often overlooked, plays a significant role in body mechanics and stability. Understanding the sacral area is important for comprehending how the spine connects to the lower limbs and supports everyday movements. It has various functions integral to physical well-being.
Locating the Sacral Area
The sacral area is located at the very bottom of the spine, directly above the tailbone. This triangular-shaped region is positioned between the two large hip bones at the back of the pelvis. It forms the posterior aspect of the pelvic girdle. You can feel it by running your hand down your lower back until you reach a flattened, bony area just above the cleft of the buttocks.
Anatomy of the Sacrum
The sacral area is defined by the sacrum, a single, triangular bone. This bone develops from the fusion of five individual vertebrae, specifically S1 through S5. The sacrum connects superiorly with the last lumbar vertebra (L5) at its base, forming a crucial joint for spinal mobility. Laterally, it articulates with the ilium, which are parts of the hip bones, at the L-shaped sacroiliac (SI) joints. These joints are reinforced by strong ligaments, contributing to pelvic stability.
The sacrum also features several openings, known as sacral foramina, which allow for the passage of sacral nerves and blood vessels. Internally, the sacral canal runs through the center of the sacrum, housing the lower fibers of the cauda equina, a bundle of spinal nerves.
Functions of the Sacral Region
The sacral region bears and transmits the weight of the upper body to the lower limbs. The sacrum’s robust structure provides significant stability to the pelvis and spine. Its connections to the hip bones via the sacroiliac joints are important for this stability. The sacral area also protects the sacral nerves that pass through its foramina, which are essential for sensation and movement in the lower extremities and for pelvic organ function. Numerous muscles and ligaments attach to the sacrum, contributing to posture, movement, and overall spinal support.
Common Sacral Area Conditions
Several conditions can affect the sacral area, often leading to discomfort or pain. One common issue is sacroiliac (SI) joint dysfunction, which involves abnormal movement—either too much or too little—in the SI joints. This dysfunction can cause pain in the lower back, buttocks, hips, and sometimes radiate down the leg, mimicking sciatica. Sacroiliitis, which is inflammation of the SI joint, is another condition that can cause similar pain, often worsened by prolonged sitting or standing.
Causes for sacral pain and sacroiliitis can include trauma from falls or accidents, arthritis (such as osteoarthritis or ankylosing spondylitis), pregnancy due to hormonal changes and added weight, and infection. Symptoms can vary, ranging from a dull ache to sharp, stabbing pain, and may also include stiffness or a feeling of instability in the pelvis.