Distal interphalangeal joints are involved in all except –
**Core Concept**
Distal interphalangeal (DIP) joints are small, hinge-like joints located at the tip of the fingers and toes. They are involved in various rheumatological conditions and are a common site for osteoarthritis.
**Why the Correct Answer is Right**
The correct answer is related to the involvement of DIP joints in certain conditions. DIP joints are typically spared in rheumatoid arthritis (RA), a chronic autoimmune disorder characterized by inflammation and destruction of joints. In contrast, osteoarthritis (OA) often affects DIP joints, leading to wear and tear, pain, and stiffness. The involvement of DIP joints in OA is due to the high stress and strain on these joints, particularly in individuals with a history of repetitive hand or foot use.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option might be incorrect if it suggests a condition that typically spares DIP joints, such as RA.
* **Option B:** This option might be incorrect if it suggests a condition that commonly affects DIP joints, such as OA.
* **Option C:** This option might be incorrect if it suggests a condition that affects DIP joints, such as psoriatic arthritis.
* **Option D:** This option might be incorrect if it suggests a condition that affects DIP joints, such as gout.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that DIP joints are typically spared in RA, making them a useful differentiator between RA and OA. When evaluating patients with joint pain or arthritis, consider the involvement of DIP joints to help guide your diagnosis.
**Correct Answer: A.**