**Core Concept**
Rheumatoid arthritis (RA) is a chronic autoimmune disorder characterized by inflammation and destruction of joints, leading to characteristic radiographic changes. The X-ray findings of RA are crucial for diagnosis and monitoring disease progression.

**Why the Correct Answer is Right**
The correct answer is one of the options that does not represent a typical X-ray finding of RA. RA is associated with joint space narrowing, subchondral bone erosions, and periarticular osteopenia. These changes occur due to inflammation and destruction of the joint cartilage and underlying bone. The characteristic "joint space narrowing" is a result of cartilage destruction, while "subchondral bone erosions" are a consequence of bone resorption by inflammatory cells.

**Why Each Wrong Option is Incorrect**
* **Option A:** Joint space narrowing is a common finding in RA, resulting from cartilage destruction. This is a characteristic X-ray feature of the disease.
* **Option B:** Periarticular osteopenia is a common finding in RA, resulting from decreased bone density in the surrounding bone due to inflammation and decreased bone turnover. This is a characteristic X-ray feature of the disease.
* **Option C:** Subchondral bone erosions are a common finding in RA, resulting from bone resorption by inflammatory cells. This is a characteristic X-ray feature of the disease.

**Clinical Pearl / High-Yield Fact**
In RA, the presence of subchondral bone erosions on X-ray is a hallmark of disease progression and a predictor of poor prognosis. Early detection of erosions is crucial for timely intervention and management.

**Correct Answer:** D