In a study of 200 patients with acute gouty arthritis in an urban Indian hospital, the most common site of initial presentation was identified. Which joint is the most common site of first attack in primary gout?

Explanation

## Most Common Site of Gout: First Metatarsophalangeal Joint **Key Point:** The first metatarsophalangeal joint (hallux or "big toe") is affected in the first attack of gout in approximately 50% of patients and is the most common site overall. ### Anatomical and Pathophysiological Basis #### Why the First MTP Joint? 1. **Lowest temperature in the body** - Peripheral joints are cooler than central joints - Monosodium urate (MSU) crystals have decreased solubility at lower temperatures - First MTP joint is the most distal and coldest major joint 2. **Highest mechanical stress** - Bears significant weight during walking and standing - Repetitive microtrauma predisposes to crystal deposition - Foot is in constant motion, creating local inflammation 3. **Synovial fluid characteristics** - Lower pH in peripheral joints favors MSU crystallization - Reduced blood flow in distal joints = slower urate clearance 4. **Anatomical factors** - Smaller joint space with limited volume - Cartilage composition favors crystal nucleation ### Frequency of Involvement by Site | Joint | Frequency in First Attack | Frequency Overall | |-------|---------------------------|-------------------| | First MTP (hallux) | ~50% | ~70% | | Ankle | ~20% | ~30% | | Knee | ~10% | ~25% | | Wrist | ~5% | ~10% | | Other joints | ~15% | Variable | **Clinical Pearl:** The term **"podagra"** specifically refers to gout of the foot (first MTP joint), and is the classic presentation. A patient presenting with acute monoarticular arthritis of the hallux with elevated serum uric acid should raise immediate suspicion for acute gout. ### Mnemonic for Gout Sites: **"ANKLES"** - **A**nkle - **N**eck (wrist) - **K**nee - **L**ower extremity (foot/hallux) — **MOST COMMON** - **E**lbow - **S**houlder (rare) **High-Yield:** While any joint can be affected (polyarticular gout in chronic disease), the **first MTP joint is the pathognomonic initial site** and should be the first to examine in a patient with suspected gout. ### Clinical Presentation - Sudden onset of severe pain, swelling, erythema, and warmth - Often nocturnal onset - Severe enough to prevent weight-bearing - Resolves spontaneously in 7–10 days even without treatment - Recurrence rate: ~62% within 1 year if uric acid not controlled [cite:Harrison 21e Ch 297; Park 26e Ch 3]