Crystal arthritis most commonly refers to which condition?

• A. Gout
• B. Osteoarthritis
• C. Psoriatic arthritis
• D. Rheumatoid arthritis

Answer: (A)

Crystal arthritis refers to inflammatory arthritis driven by crystal deposition in a joint. The most common crystal involved is monosodium urate, which forms when uric acid is elevated, leading to gout. This condition typically presents as a sudden, extremely painful, swollen joint—most famously the big toe. Under polarized light microscopy, the urate crystals appear needle-shaped and negatively birefringent, which helps confirm the diagnosis. While there are other crystal-related arthritides, such as calcium pyrophosphate deposition disease (pseudogout), gout is by far the most common. Other autoimmune inflammatory arthritides like rheumatoid arthritis and psoriatic arthritis are not defined by crystal deposition, making gout the go-to reference for crystal arthritis.