**Core Concept**
Gout is a form of inflammatory arthritis characterized by the deposition of monosodium urate crystals in the joints, leading to the formation of tophi, which are deposits of uric acid crystals and calcium pyrophosphate dihydrate crystals. Tophi are typically found in the soft tissues and are a hallmark of chronic gout.

**Why the Correct Answer is Right**
Tophi are the result of the accumulation of monosodium urate crystals in the soft tissues, which can occur in response to chronic hyperuricemia. The deposition of these crystals can lead to the formation of tophi, which are typically found in the skin, cartilage, and synovial membranes. The pathogenesis of tophus formation involves the precipitation of uric acid crystals in the presence of high levels of uric acid, which can occur in patients with chronic gout.

**Why Each Wrong Option is Incorrect**
**Option A:** Osteoarthritis - Osteoarthritis is a degenerative joint disease characterized by the breakdown of cartilage and the formation of bone spurs, but it is not associated with the formation of tophi.

**Option B:** Rheumatoid Arthritis - Rheumatoid arthritis is an autoimmune disease characterized by the inflammation of the joints, but it is not associated with the formation of tophi.

**Option C:** Pseudogout - Pseudogout is a form of arthritis characterized by the deposition of calcium pyrophosphate dihydrate crystals in the joints, but it is not associated with the formation of tophi.

**Clinical Pearl / High-Yield Fact**
Tophi are typically found in the skin, cartilage, and synovial membranes, and can be seen as yellowish or whitish nodules. They can also be found in other areas, such as the cartilage of the ears and the helix of the ear.

**Correct Answer: C. Pseudogout is not correct; the correct answer is actually Gout.**