The pudendal nerve in females runs deep within the pelvis, originating from the lower spine and traveling a looping path through the buttock region before reaching the perineum, the area between the vaginal opening and the anus. It passes closest to the surface near a bony landmark called the ischial spine, which sits along the back wall of the pelvis on each side. Understanding where this nerve sits helps explain why certain types of pelvic pain, bladder issues, or sexual dysfunction occur, and why prolonged sitting can make them worse.
Where It Starts: The Lower Spine
The pudendal nerve forms from three nerve roots that exit the spinal cord at the sacrum, the triangular bone at the base of your spine. These roots come from levels S2, S3, and S4. They merge together along the lateral wall of the pelvic cavity to form a single nerve trunk. Because it draws from multiple spinal levels, the pudendal nerve carries both sensory fibers (allowing you to feel touch, pressure, and pain) and motor fibers (controlling specific muscles in the pelvic floor).
The Looping Path Through the Pelvis
What makes the pudendal nerve unusual is that it doesn’t travel in a straight line. After forming inside the pelvis, it exits through the greater sciatic notch, a gap in the back of the pelvis near the piriformis muscle in the buttock. It then immediately hooks around the ischial spine, a small bony projection you can think of as a knob on the inner wall of the pelvis, and re-enters the pelvic region through the lesser sciatic notch.
During this U-turn, the nerve passes through a tight corridor between two ligaments: the sacrospinous ligament and the sacrotuberous ligament. This “clamp” between the ligaments is one of the most clinically important spots along the nerve’s path because it’s a common site where the nerve gets compressed or irritated.
The Pudendal Canal
Once the nerve re-enters the pelvis, it travels forward through a tunnel called the pudendal canal (sometimes called Alcock’s canal). This canal is a tube-like space formed by a split in the tissue covering the obturator internus muscle, one of the deep hip rotator muscles that lines the inner sidewall of the pelvis. The canal begins near the ischial spine and extends forward toward the front of the pelvis, running along the outer wall of the fat-filled space beside the rectum.
Inside this canal, the nerve is accompanied by the internal pudendal artery and vein. The canal provides a protected passageway, but it’s also another potential compression point. Spasm of the obturator internus muscle can squeeze the nerve within the canal, producing pain and tenderness deep in the pelvis.
Three Branches and What They Reach
As the pudendal nerve travels through and beyond the canal, it splits into three terminal branches, each serving a different part of the perineum and pelvic floor:
- Inferior rectal nerve: This branch supplies sensation to the skin around the anus and provides motor control to the external anal sphincter, the muscle you consciously tighten to control bowel movements.
- Perineal nerve: The largest branch, it provides sensation to the labia, the lower vagina, and the skin of the perineum. It also controls several pelvic floor muscles involved in urinary continence and vaginal support.
- Dorsal nerve of the clitoris: This purely sensory branch runs forward along the inner surface of the pubic bone to reach the clitoris. It is the primary nerve responsible for clitoral sensation and plays a central role in sexual arousal and orgasm.
Together, these three branches mean the pudendal nerve is involved in nearly everything happening in the female perineum: bladder and bowel control, sexual sensation, and the ability to contract or relax the pelvic floor muscles.
Key Landmark: The Ischial Spine
The ischial spine is the single most important landmark for locating the pudendal nerve. In a clinical setting, a provider can feel the ischial spine by pressing along the posterolateral wall of the vagina. The nerve consistently passes immediately behind and just medial to the tip of this bony point, though its exact position varies slightly from person to person.
This is why nerve blocks for pelvic pain target a spot roughly 1 centimeter medial and slightly below the ischial spine. The sacrospinous ligament, which attaches to the spine, serves as a secondary guide. If the ischial spine itself is hard to feel, a provider can trace the firm band of the sacrospinous ligament from the sacrum outward until it reaches the spine. The nerve sits in loose tissue just behind the ligament at this level.
Where the Nerve Gets Trapped
The pudendal nerve’s winding path creates four distinct sites where compression can occur, classified as types I through IV. Type II, at the ischial spine between the sacrospinous and sacrotuberous ligaments, is the most common. Type I involves entrapment as the nerve exits below the piriformis muscle and is often linked to piriformis spasm. Type III occurs at the entrance of the pudendal canal, typically related to obturator internus muscle spasm. Type IV affects the terminal branches further along.
Common triggers for entrapment include prolonged sitting (especially cycling), childbirth trauma, pelvic fractures, and prior pelvic surgery. Each site produces a slightly different pattern of tenderness. Entrapment near the greater sciatic notch causes tenderness over that area in the buttock. Compression at the ischial spine produces pain felt medially, deep to the sit bone. Entrapment within the pudendal canal causes obturator internus spasm and tenderness along the inner pelvic wall.
How Its Location Relates to Symptoms
Because the pudendal nerve serves such a wide territory, problems along any point of its path can produce symptoms that seem unrelated at first glance. Pain or burning in the vulva, difficulty holding urine, pain with sitting that improves when standing, numbness around the anus, or reduced clitoral sensation can all trace back to the same nerve. The specific combination of symptoms often points to where along the nerve’s course the problem is occurring.
Sitting worsens symptoms in most cases because body weight compresses the nerve against the ischial spine and within the pudendal canal. This is why people with pudendal nerve issues often report relief when sitting on a toilet seat, which removes direct pressure from the perineum, or when using a cushion with a cutout in the center.