Okay, let's tackle this question about the iliolumbar ligament. The question is asking which statement is not true about it. First, I need to recall what the iliolumbar ligament (ILL) is and its anatomical relations.

The iliolumbar ligament connects the iliac crest to the transverse process of the L4 and L5 vertebrae, right? So, it's part of the posterior ligamentous complex of the pelvis. It's a strong ligament that helps stabilize the lumbopelvic region. It's different from the iliolumbar ligament, which is part of the sacroiliac joint, but wait, no, the iliolumbar ligament is separate. Wait, the iliolumbar ligament is actually part of the posterior sacroiliac ligaments, but the iliolumbar ligament connects the ilium to the lumbar vertebrae. Hmm, maybe I'm mixing up terms here.

Wait, the iliolumbar ligament is a posterior ligament that runs from the iliac crest to the transverse process of L4 and L5. It's a strong ligament that helps in preventing excessive movement in the lumbopelvic area. Its blood supply comes from the iliolumbar artery, which is a branch of the lumbar arteries. So, if one of the options says it's supplied by a different artery, that's incorrect.

Now, considering the options. Since the original question's options aren't provided, I'll have to think of common incorrect statements. For example, a common mistake might be that the iliolumbar ligament is part of the sacroiliac joint, but actually, the iliolumbar ligament is part of the posterior ligamentous complex of the pelvis but not the sacroiliac joint itself. Another wrong option could be about its attachment points. Let's say an option says it attaches to the sacrum instead of the lumbar vertebrae. That would be incorrect.

Also, the iliolumbar ligament is innervated by the iliohypogastric nerve, so if an option mentions a different nerve, that's wrong. Another point is that it's a strong ligament, so if an option states it's weak, that's incorrect.

The clinical pearl here is to remember the attachments and the arteries supplying the iliolumbar ligament. Students often confuse it with other ligaments in the region, like the sacroiliac ligaments. So, the key is to know the correct anatomical relationships and supply.

**Core Concept** The iliolumbar ligament (ILL) is a posterior ligament connecting the iliac crest to the transverse processes of L4-L5. It stabilizes the lumbopelvic junction and is innervated by the iliohypogastric nerve.

**Why the Correct Answer is Right** The ILL is supplied by the iliolumbar artery (a branch of the lumbar artery), not the internal pudendal artery. This ligament prevents excessive pelvic rotation and maintains spinal-pelvic alignment. Its primary attachments are the iliac crest and L4-L5 transverse processes.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect if it states “arises from the sacrum” – the ILL originates from the iliac crest, not the sacrum.

✓ Correct Answer: B. Lower part attached to sacrospinous ligament