**Core Concept**
The question is testing the understanding of the early radiological changes in Rheumatoid Arthritis (RA), a chronic autoimmune disorder characterized by inflammation and destruction of joints. The earliest changes in RA are subtle and often overlooked, but recognizing them is crucial for early diagnosis and treatment.

**Why the Correct Answer is Right**
The correct answer is related to the earliest radiological change in RA, which is **periarticular erosions**. These erosions occur due to the inflammatory process and are often seen as small, well-defined defects in the cortical bone. They are typically seen in the metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints. The inflammation in RA causes the release of various cytokines and chemokines, which lead to the activation of osteoclasts, resulting in bone resorption and erosion.

**Why Each Wrong Option is Incorrect**
* **Option A:** Soft tissue swelling is an early feature of RA, but it is not the earliest radiological change.
* **Option B:** Joint space narrowing is a later feature of RA, which occurs due to cartilage destruction.
* **Option C:** Osteopenia is a feature of chronic inflammation, but it is not the earliest radiological change in RA.

**Clinical Pearl / High-Yield Fact**
It is essential to recognize that the earliest radiological changes in RA can be subtle and may not be present in the initial stages. Therefore, a high index of suspicion and a careful clinical examination, along with laboratory tests, are crucial for early diagnosis.

**Correct Answer: C. Osteopenia.**