**Question:** Structure crossing the dorsal surface of ischial spine are A/E:

A. Sacral nerve roots
B. Sacroiliac joint
C. Sacrospinous ligament
D. Sacrotuberous ligament

**Core Concept:** The ischial spine is a bony projection of the pelvic ring, located on the posterior aspect of the sacrum. The dorsal surface of the ischial spine is crossed by several important structures involved in the anatomy and function of the pelvic region.

**Why the Correct Answer is Right:**

Correct Answer: D. Sacrotuberous ligament

The sacrotuberous ligament (Figure 1) is a strong, dense band of connective tissue that connects the ischial spine to the tuberosity of the ischium on one side and the iliac crest on the other side. It plays a crucial role in the stability of the pelvic region, particularly in maintaining the integrity of the pelvic girdle.

**Why Each Wrong Option is Incorrect:**

A. Sacral nerve roots: The sacral nerve roots (S1, S2, S3) are located beneath the sacrum, not on the dorsal surface of the ischial spine. They primarily innervate the lower limbs and genitalia.

B. Sacroiliac joint: The sacroiliac joint is a synovial joint connecting the sacrum to the ilium and is located more laterally, not on the dorsal surface of the ischial spine. The sacroiliac joint is a major joint involved in the mobility and stability of the pelvic girdle.

C. Sacrospinous ligament: The sacrospinous ligament (Figure 2) is a strong, dense band of connective tissue that connects the ischial spine to the spinous process of the coccyx. It is located more ventrally (below) on the ischial spine, not on the dorsal surface.

**Clinical Pearl:**

The sacrotuberous ligament is an essential structure for maintaining pelvic stability and helping to support the weight of the upper body when we stand upright. Injuries to this structure can lead to instability and pain in the lower back and pelvis, which is crucial to recognize and understand for proper diagnosis and treatment planning. In clinical practice, physicians should consider the role of the sacrotuberous ligament when examining patients with low back pain, pelvic pain, or instability complaints.

**Why to Memorize:**

Understanding the anatomy and function of the sacrotuberous ligament is essential for:

1. Diagnosing patients with low back pain, pelvic pain, or instability complaints.
2. Formulating an appropriate treatment plan for these patients, including exercises, physical therapy, or referral to a specialist when necessary.
3. Recognizing the importance of the sacrotuberous ligament in maintaining pelvic stability and understanding its potential injuries.