Gout and pseudogout are both crystal arthritis, meaning sudden, intensely painful joint inflammation caused by crystals, but the crystals are different, and so is nearly everything downstream. Gout is caused by uric acid (monosodium urate) crystals and classically strikes the big toe; pseudogout is caused by calcium pyrophosphate (CPP) crystals and favors the knee and wrist. Gout has a definitive long-term fix (lowering uric acid); pseudogout doesn’t, but it does have effective flare treatment and, importantly, a short list of underlying conditions worth checking for. Because the flares can look identical, even experienced physicians can’t reliably tell them apart without testing. The Side-by-Side Comparison Feature Gout Pseudogout (CPPD) Crystal Monosodium urate (uric acid) Calcium pyrophosphate (CPP) Classic joint Big toe (also ankle, midfoot, knee) Knee (also wrist, shoulder, ankle) Typical age Men 30s-50s; women after menopause Mostly over 60; very common over 80 Flare onset Explosive, often overnight Rapid, but often somewhat slower to peak Blood clue Elevated uric acid (usually) None specific; normal uric acid X-ray clue Erosions in long-standing disease Chondrocalcinosis: cartilage calcification Definitive test Needle-shaped urate crystals in joint fluid Rhomboid CPP crystals in joint fluid Long-term fix Yes: lower uric acid below 6 mg/dL No crystal-dissolving therapy yet Linked conditions Kidney disease, metabolic syndrome, diuretics Hyperparathyroidism, hemochromatosis, low magnesium, hypothyroidism Flare treatment Colchicine, NSAIDs, steroids Essentially the same big toe in a middle-aged man with high uric acid, think gout. Knee or wrist in a patient over 70 with calcification on X-ray, think pseudogout. But the …
Gout vs. Pseudogout: How to Tell the Difference
Gout and pseudogout are both crystal arthritis, meaning sudden, intensely painful joint inflammation caused by crystals, but the crystals are different, and so is nearly everything downstream. Gout is caused by uric acid (monosodium urate) crystals and classically strikes the big toe; pseudogout is caused by calcium pyrophosphate (CPP) crystals and favors the knee and wrist. Gout has a definitive long-term fix (lowering uric acid); pseudogout doesn’t, but it does have effective flare treatment and, importantly, a short list of underlying conditions worth checking for. Because the flares can look identical, even experienced physicians can’t reliably tell them apart without testing.
The Side-by-Side Comparison
| Feature | Gout | Pseudogout (CPPD) |
|---|---|---|
| Crystal | Monosodium urate (uric acid) | Calcium pyrophosphate (CPP) |
| Classic joint | Big toe (also ankle, midfoot, knee) | Knee (also wrist, shoulder, ankle) |
| Typical age | Men 30s-50s; women after menopause | Mostly over 60; very common over 80 |
| Flare onset | Explosive, often overnight | Rapid, but often somewhat slower to peak |
| Blood clue | Elevated uric acid (usually) | None specific; normal uric acid |
| X-ray clue | Erosions in long-standing disease | Chondrocalcinosis: cartilage calcification |
| Definitive test | Needle-shaped urate crystals in joint fluid | Rhomboid CPP crystals in joint fluid |
| Long-term fix | Yes: lower uric acid below 6 mg/dL | No crystal-dissolving therapy yet |
| Linked conditions | Kidney disease, metabolic syndrome, diuretics | Hyperparathyroidism, hemochromatosis, low magnesium, hypothyroidism |
| Flare treatment | Colchicine, NSAIDs, steroids | Essentially the same |
big toe in a middle-aged man with high uric acid, think gout. Knee or wrist in a patient over 70 with calcification on X-ray, think pseudogout. But the overlap is large enough that joint-fluid analysis remains the gold standard.
What Each Disease Actually Is
Gout develops when uric acid stays above its saturation point (about 6.8 mg/dL) long enough for crystals to form in joints. Flares occur when the immune system attacks those crystals. Uric acid levels are largely driven by genetics and kidney handling, which is why gout runs in families and why diet alone rarely fixes it.
Pseudogout, formally calcium pyrophosphate deposition disease (CPPD), develops when CPP crystals form in cartilage. Deposition increases sharply with age: cartilage calcification is present in a large share of people over 80, though most never flare. When crystals do shed into the joint, the resulting attack is clinically indistinguishable from gout, hence the name. CPPD wears other masks too: it can smolder like rheumatoid arthritis (“pseudo-RA”) or accelerate osteoarthritis in unusual joints, which is why it’s nicknamed rheumatology’s “great mimic.”
How Doctors Tell Them Apart
- Joint aspiration, the gold standard. Fluid drawn from the joint is examined under polarized microscopy: needle-shaped, negatively birefringent crystals mean gout; rhomboid, weakly positively birefringent crystals mean CPPD. Aspiration also rules out the third and most dangerous look-alike, joint infection, which can mimic both and is an emergency.
- Imaging. X-rays showing chondrocalcinosis (thin calcium lines in cartilage of the knee or wrist) support CPPD; ultrasound and dual-energy CT can visualize urate deposits in gout.
- Blood work. Uric acid supports gout when elevated, but it can be misleadingly normal during a flare, so it never settles the question alone. There is no blood test for pseudogout.
- Pattern over time. Joint distribution, age, triggers (pseudogout flares classically follow surgery, injury, or acute illness), and treatment response all inform the picture.
Why the Distinction Changes Your Care
- Gout has a long-term cure-adjacent strategy; pseudogout doesn’t. Confirmed gout means urate-lowering therapy can dissolve the crystal burden and end the disease’s progression. No equivalent exists for CPP crystals. Prescribing allopurinol for “gout” that’s actually pseudogout treats nothing.
- Pseudogout triggers a metabolic checklist. New CPPD, especially under age 60 or in unusual severity, should prompt screening for hyperparathyroidism, hemochromatosis (iron overload), hypomagnesemia, and hypothyroidism. Finding and treating one of these is a genuine win that generic “arthritis” care misses.
- Recurrent pseudogout has a prevention option. Low-dose daily colchicine can reduce flare frequency in repeat offenders.
- Both deserve confirmation before decades of treatment. Committing a patient to lifelong medication, or dismissing recurrent “gout” that never responds, warrants crystal-level certainty.
Frequently Asked Questions
It can be. Pseudogout flares cause the same swollen, hot, exquisitely tender joint. Patients and physicians cannot reliably distinguish the two by pain alone. Gout flares tend to peak slightly faster, but the overlap is substantial.
Yes. Both become more common with age and can even coexist in the same joint. This is another argument for joint-fluid analysis when flares behave unexpectedly or don’t respond to treatment as predicted.
Flares often follow joint injury, surgery (including unrelated procedures), or acute medical illness, and sometimes occur without any identifiable trigger. Underlying contributors include hyperparathyroidism, hemochromatosis, low magnesium, and hypothyroidism, which is why new pseudogout warrants metabolic screening.
No. Allopurinol lowers uric acid, which has no role in calcium pyrophosphate deposition. Pseudogout treatment centers on controlling flares (NSAIDs, colchicine, or steroids), plus prophylactic colchicine for frequent attacks and treatment of any underlying metabolic condition.
Get Crystal-Level Certainty. See Dr. Dhillon by Video This Week.
Recurrent joint attacks deserve a definitive answer, not a decade of treating the wrong crystal. Dr. Dhillon, a board-certified rheumatologist, sees new patients by secure video visit from your home, usually within the same week, with records reviewed before every visit. No referral required. Video visits are available to patients located in California; joint aspiration and in-person care are available in Beverly Hills.
Book a Video Visit, or call for a 15 minute discovery call at +1 (949) 209-4716.
This article is for educational purposes and is not a substitute for personalized medical advice, diagnosis, or treatment. A hot, swollen joint with fever may indicate infection. Seek immediate care.
