Pudendal nerve entrapment happens when the pudendal nerve, which runs through the pelvis and supplies sensation to the genitals, perineum, and rectum, gets compressed or pinched along its path. The most common cause is compression between two ligaments deep in the pelvis, but cycling, childbirth, pelvic surgery, chronic straining, and muscle problems can all trigger it. The condition affects up to 1% of the population, with women more than twice as commonly affected as men.
Where the Nerve Gets Trapped
The pudendal nerve travels a winding route through the pelvis, and there are specific pinch points where compression tends to happen. Understanding these helps explain why so many different activities and injuries can lead to the same problem.
The most common site is where the nerve passes between two ligaments called the sacrospinous and sacrotuberous ligaments, near a bony landmark called the ischial spine. This is classified as Type II entrapment, and it accounts for the majority of cases. The nerve threads through a narrow gap between these two tough bands of tissue, and anything that causes swelling, scarring, or tightening in this area can squeeze it.
The second major site is the entrance to a small tunnel called the Alcock canal (or pudendal canal), which runs along the inner wall of the pelvis. Type III entrapment occurs here, often linked to spasm or swelling in a nearby muscle called the obturator internus, which forms part of the canal wall. When that muscle is inflamed or in spasm, the canal narrows and the nerve has nowhere to go.
Cycling and Prolonged Sitting
Cycling is one of the best-documented causes of pudendal nerve compression. When you sit on a bicycle saddle, your body weight presses the perineum (the area between the sit bones) against the hard, narrow seat. The nerve gets sandwiched between the saddle and the pubic bones, cutting off blood flow and compressing the nerve directly.
A forward-leaning posture, common in road cycling, makes this worse by pressing the perineum forward against the ischial spine. Triathlon-style handlebars shift the body even further forward, increasing perineal pressure. An upward-tilted seat also concentrates more force on the nerve. Over time, repeated compression causes scarring (fibrosis) within the pudendal canal and the surrounding ligaments, turning temporary irritation into a chronic problem.
The duration of compression matters. Research suggests that if the nerve loses blood flow for less than six hours, the blockage in nerve signaling reverses quickly. But if that ischemic period extends beyond eight hours, recovery can take weeks. For cyclists, some authors recommend standing on the pedals for 20 to 30 seconds every 20 minutes to relieve pressure. Prolonged sitting on any hard surface, not just a bike seat, can produce similar effects over time.
Childbirth Trauma
Vaginal delivery is a recognized cause of pudendal nerve injury. During childbirth, the baby’s head passes through the pelvic floor, stretching the pudendal nerve beyond its normal limits. The nerve is particularly vulnerable where it wraps around the ischial spine, the same bony point where Type II entrapment occurs. The combination of sustained pressure and stretching during a prolonged or difficult labor can damage the nerve directly or trigger inflammation and scarring that leads to entrapment later.
This mechanism helps explain why women are disproportionately affected by the condition. In one study of 81 patients with pudendal neuralgia, 53 were female and 28 were male. While not every case in women traces back to childbirth, it remains one of the most significant risk factors specific to this population.
Pelvic Surgery and Mesh Implants
Surgical procedures in the pelvis can injure the pudendal nerve directly or create scar tissue that traps it afterward. Vaginal mesh surgery is a particularly notable culprit. Cases have been documented where patients developed severe, persistent pelvic pain after rectocele repair using mesh and after tension-free vaginal tape sling procedures. The mesh can cause mechanical distortion of the nerve or trigger a fibrotic response that slowly tightens around it.
Other pelvic surgeries, including procedures for pelvic fractures and hip operations, carry similar risks. The nerve’s location deep in the pelvis, close to bone and ligament, means that any surgical hardware, sutures, or scar tissue in the area can encroach on it. The resulting pain can appear weeks to months after surgery, making it harder to connect cause and effect.
Muscle Spasm and the Obturator Internus
The obturator internus muscle, which lines part of the inner pelvic wall and forms one boundary of the Alcock canal, plays a direct role in some cases. When this muscle goes into chronic spasm, swells, or develops fibrosis, it compresses the nerve within the canal. Case reports have documented pudendal neuropathy caused by edema (swelling) of the obturator internus, confirmed on MRI imaging.
Pelvic floor muscle dysfunction more broadly can contribute. Chronic tightness in the muscles surrounding the nerve creates sustained pressure. This is why pelvic floor physical therapy is often part of treatment: releasing muscle tension can relieve the mechanical compression driving the symptoms.
Chronic Straining and Constipation
Repetitive straining during bowel movements is an underappreciated cause. In women with chronic constipation and abnormal perineal descent (where the pelvic floor drops lower than normal during straining), researchers found progressive nerve damage that worsened over time. Patients with a longer history of straining showed more severe neurogenic damage to the external anal sphincter and its pudendal nerve supply than those with a shorter history.
The mechanism is cumulative. Each episode of heavy straining pulls the pelvic floor downward, stretching the pudendal nerve where it’s anchored at the ischial spine. Over months and years, this repeated traction causes gradual denervation, weakening the muscles the nerve controls and producing the burning, stabbing pain characteristic of pudendal neuralgia.
Pelvic Fractures and Direct Trauma
A fracture of the pelvis can damage the pudendal nerve through direct impact, displacement of bone fragments, or the swelling and scarring that follow. Falls onto the buttocks, particularly onto hard surfaces, are a common scenario. Even without a fracture, a heavy fall can bruise or stretch the nerve at its vulnerable points near the ischial spine.
How Entrapment Is Identified
Because pudendal nerve entrapment mimics many other pelvic pain conditions, clinicians use a specific set of criteria known as the Nantes criteria to make the diagnosis. All five must be present: pain in the territory the pudendal nerve supplies, pain that worsens with sitting, pain that does not wake you from sleep at night, no measurable loss of sensation on examination, and improvement after a nerve block injection that numbs the pudendal nerve.
The “not woken at night” criterion is particularly useful. It distinguishes nerve entrapment from inflammatory or tumor-related pain, which tends to persist regardless of position. Entrapment pain is position-dependent: sitting compresses the nerve, lying down relieves it. If your pain follows this pattern and matches the nerve’s territory (genitals, perineum, rectum), entrapment becomes a strong possibility. MRI can sometimes reveal the structural cause, such as muscle swelling or scarring around the nerve, though imaging is normal in many confirmed cases.