**Core Concept**
Rheumatoid arthritis (RA) is a chronic autoimmune disorder characterized by inflammation of the synovial joints, leading to pain, swelling, and eventually, joint destruction. The disease involves a complex interplay between genetic and environmental factors, resulting in the production of autoantibodies and the activation of various inflammatory pathways.

**Why the Correct Answer is Right**
C-reactive protein (CRP) is a marker of inflammation that is often elevated in patients with active RA. However, high levels of CRP are associated with a poor prognosis, as they indicate active inflammation and joint damage. In contrast, patients with lower levels of CRP tend to have a better prognosis, as they are less likely to experience severe joint damage and other complications. This is because CRP is a marker of the body's inflammatory response, and high levels indicate ongoing inflammation and tissue damage.

**Why Each Wrong Option is Incorrect**
**Option A:** Anti-IgG antibodies, specifically rheumatoid factor (RF), are commonly found in patients with RA and are used as a diagnostic marker. However, not all patients with RA are positive for RF, and some individuals without RA may also test positive.

**Option B:** Juxta-articular osteoporosis is a common feature of RA, resulting from the inflammatory process and the subsequent loss of bone density. This occurs due to the increased activity of osteoclasts, which break down bone tissue, and the decreased activity of osteoblasts, which form new bone tissue.

**Option C:** Morning stiffness is a characteristic symptom of RA, lasting for more than an hour and improving with movement. This occurs due to the inflammatory process and the subsequent swelling of the synovial joints, which leads to stiffness and limited range of motion.

**Clinical Pearl / High-Yield Fact**
It's essential to note that patients with RA who have a low titer of rheumatoid factor (RF) or are RF-negative are more likely to have a better prognosis and respond well to treatment.

**✓ Correct Answer: D. C Reactive protein indicates better prognosis**