Okay, let's tackle this question about ankylosing spondylitis. The question is asking which joint is the last to be involved. First, I need to recall the typical progression of ankylosing spondylitis. I remember that it's a type of spondyloarthritis that primarily affects the axial skeleton, starting in the sacroiliac joints. So the sacroiliac joints are usually the first to be affected.

Now, the progression moves upward. The spine is involved next, especially the lumbar region. Then it can affect the thoracic and cervical spine. But the question is about the last joint. Wait, maybe it's about peripheral joints? Ankylosing spondylitis can also involve peripheral joints, but those are usually later in the course. Common peripheral joints affected include the hips, knees, and shoulders. But which one is the last?

I think the hips are often involved in the later stages. But wait, the sacroiliac joints are first. Then the spine, and then maybe the hips? Or is there another joint? The question is a bit tricky. Let me think. The sacroiliac joints are first, then the spine, and the hips can become involved later. But maybe the last joint is the hip? Or perhaps the cervical spine? Wait, cervical spine involvement can lead to atlanto-axial subluxation, which is a serious complication. That might be considered a late finding.

But the options here are not listed, so I have to assume the correct answer is the hip joint. Wait, the user mentioned that the correct answer is C, but the options are not provided. Wait, the user's correct answer is missing in the input. Let me check again. The user provided the correct answer as ". " but the options are A, B, C, D without text. Hmm, maybe there was a formatting error. Wait, the original question's options are empty, but the correct answer is given as C? Or maybe there was a mistake in the input. Wait, the user's question says "Correct Answer: . " but the options are A-D with no text. This is confusing. How can I proceed without knowing the options?

Wait, perhaps the user made a mistake in the input. The question is about the last joint involved in ankylosing spondylitis. The correct answer is usually the hip joint. But let me confirm. In ankylosing spondylitis, the sacroiliac joints are the first to be affected. Then the spine, and the peripheral joints, such as hips, knees, and shoulders, are involved later. The hip joint is a common site of involvement in the later stages. So if the options included hip, that would be the correct answer. Alternatively, the cervical spine is involved later. But the question is about the last joint. So maybe the hip is the last. Alternatively, maybe the knee. But I need to verify.

Another thought: ankylosing spondylitis typically starts in the sacroiliac joints and ascends the spine. Peripheral joints can be involved, but the hips are often affected in later stages. So if the options included the hip joint, that would be the correct answer. Therefore, assuming that the correct answer is the hip joint, the explanation would focus on the progression from sacroiliac to spine to hips. The other joints like

✓ Correct Answer: B. Temporo mandibular joint