Obturator internus

Scientific basis

The obturator internus lines part of the lateral wall of the pelvis. Its tendon leaves the pelvis through the lesser sciatic notch before reaching the femur. Alcock's canal is classically described as a canal formed by a splitting of the obturator internus fascia. A recent cadaver study (Chikazawa et al., 2026) instead places the pudendal nerve within a fascia derived from the sacrotuberous ligament, without it passing through the obturator internus fascia proper — an anatomical refinement that adds to the classical description rather than replacing it.

Blue Portance / SBNFA™ reading

This anatomical relationship illustrates an important principle of the SBNFA™: muscle, fascia and nerve do not function as independent elements. Variations in tension, shape, movement, hip position and pelvic mobility can change the mechanical environment of neighboring structures.

Contribution to the analysis of sitting

The position of the hips and pelvis influences the organization of the obturator region. Seating analysis can therefore take into account both external pressures and the relationships between joint movements and deep structures.

Not to be confused with

Alcock's canal, classically associated with its fascia; piriformis, another deep muscle of the pelvic region.

Sources and scope

• Ziouziou et al. (2013): obturator internus fascia and Alcock's canal
• Hough et al. (2003): the pudendal canal and its relationship to the obturator internus muscle
• Chikazawa et al. (2026): distinguishing the obturator internus fascia from the pudendal nerve fascia
• StatPearls (2026): pudendal pathway and entrapment syndrome