Which structure serves as an attachment site for ligaments that stabilize the sacroiliac joints?

Which structure serves as an attachment site for ligaments that stabilize the sacroiliac joints?

• A. Base
• B. Promontory
• C. Sacral tuberosity
• D. Median sacral crest

Answer: (C)

The key idea is where the strong ligaments that stabilize the sacroiliac joints anchor on the sacrum. The sacral tuberosity is the rough, lateral area on the posterior sacrum where the interosseous sacroiliac ligaments attach to the sacrum (and to the ilium on the opposite side). These ligaments fill the space between the sacrum and ilium and provide most of the vertical stability for the SI joints, so this site is the primary anchor point for the ligaments that keep the joints steady. Other sacral landmarks don’t serve this primary stabilizing attachment. The base is the superior end that meets L5 and isn’t a major anchor for SI ligaments. The promontory is the anterior edge of the first sacral vertebra and isn’t the key attachment site for SI-stabilizing ligaments. The median sacral crest is a midline, posterior ridge formed by fused spinous processes and doesn’t function as the primary attachment point for these ligaments.

The key idea is where the strong ligaments that stabilize the sacroiliac joints anchor on the sacrum. The sacral tuberosity is the rough, lateral area on the posterior sacrum where the interosseous sacroiliac ligaments attach to the sacrum (and to the ilium on the opposite side). These ligaments fill the space between the sacrum and ilium and provide most of the vertical stability for the SI joints, so this site is the primary anchor point for the ligaments that keep the joints steady.

Other sacral landmarks don’t serve this primary stabilizing attachment. The base is the superior end that meets L5 and isn’t a major anchor for SI ligaments. The promontory is the anterior edge of the first sacral vertebra and isn’t the key attachment site for SI-stabilizing ligaments. The median sacral crest is a midline, posterior ridge formed by fused spinous processes and doesn’t function as the primary attachment point for these ligaments.