Which joint is most commonly affected in pseudogout –
**Core Concept**
Pseudogout, also known as calcium pyrophosphate deposition disease (CPPD), is a type of arthritis that occurs due to the accumulation of calcium pyrophosphate dihydrate crystals within the joint. This condition is characterized by sudden, severe joint pain and swelling, often mimicking the symptoms of gout. The **knee joint** is particularly susceptible to pseudogout due to its large size and weight-bearing function.
**Why the Correct Answer is Right**
The knee joint is the most commonly affected joint in pseudogout, accounting for approximately 50% of all cases. This is because the knee joint is subject to high levels of stress and strain, making it more prone to crystal deposition. The **menisci** and **cartilage** within the knee joint can also contribute to the formation of calcium pyrophosphate dihydrate crystals.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because, while other joints can be affected, they are less commonly involved than the knee.
**Option B:** Similarly, this option is incorrect as it is not the most frequently affected joint in pseudogout.
**Option D:** This option is also incorrect as the knee is the primary joint affected.
**Clinical Pearl / High-Yield Fact**
Pseudogout often presents with sudden, severe joint pain and swelling, and can be differentiated from gout by the presence of calcium pyrophosphate dihydrate crystals in the joint fluid. A key point to remember is that pseudogout can be associated with **hyperparathyroidism** and **hemochromatosis**.
**Correct Answer:** D. Knee.