**Core Concept:** Rheumatic fever is a post-infectious inflammatory condition that results from uncontrolled Streptococcus pyogenes infection, primarily affecting the heart, joints, skin, and central nervous system. It is classified based on clinical criteria, including the Jones criteria.

**Why the Correct Answer is Right:** Option C ("Arthritis in the same joint on both sides") is NOT a major criterion for rheumatic fever because it is not specific for this condition. Arthritis can be present in various other conditions like septic arthritis, gout, or even normal post-infectious transient joint inflammation.

**Why Each Wrong Option is Incorrect:**

A. **Carditis:** This is a major criterion for rheumatic fever as it represents inflammation of the heart valves, leading to heart disease.
B. **Psychosis:** This is not a criterion for rheumatic fever, as psychosis is not a part of the clinical picture for this condition.
D. **Arthritis in the same joint on both sides:** As mentioned above, this is not a major criterion for rheumatic fever due to its overlap with other conditions.

**Clinical Pearl / High-Yield Fact:** The Jones criteria, proposed in 1944, are essential to diagnose rheumatic fever. These criteria include major and minor criteria; the major criteria are carditis (heart involvement), polyarthritis (>5 joints), subacute bacterial endocarditis (SBE) prodrome, chorea (stiff-person movement disorder), and echocardiographic evidence of carditis. A minimum of 4 out of 5 major criteria or 4 out of 9 major and minor criteria are required for the diagnosis of rheumatic fever.

**Correct Answer:** C. **Arthritis in the same joint on both sides** is NOT a major criterion for rheumatic fever because it lacks specificity for the condition.