About This Page
This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
The Bottom Line
- Caused by calcium pyrophosphate dihydrate (CPPD) crystal deposition in articular cartilage
- Typically affects the KNEE (most common joint) in ELDERLY patients — contrast gout which affects 1st MTP in younger men
- Positively birefringent RHOMBOID-shaped crystals on polarised light microscopy (contrast: gout = negatively birefringent needle-shaped)
- X-ray: chondrocalcinosis (calcification of articular cartilage — especially menisci of knee, triangular fibrocartilage of wrist)
- Treatment of acute attack: NSAID, colchicine, or intra-articular/oral corticosteroid. No equivalent of allopurinol for pseudogout
Overview
Pseudogout (acute CPP crystal arthritis) is caused by deposition of calcium pyrophosphate dihydrate (CPPD) crystals in articular cartilage (chondrocalcinosis) and periarticular tissues. Crystal shedding into the joint space triggers an acute inflammatory response clinically resembling gout or septic arthritis. CPPD is classified as: acute CPP crystal arthritis (pseudogout), chronic CPP crystal inflammatory arthritis (resembling RA), and OA with CPPD. It is distinct from gout and requires different crystal identification on microscopy.
Epidemiology
CPPD prevalence increases with age — chondrocalcinosis is found in up to 30% of those over 85 years (often asymptomatic). Risk factors include advanced age (strongest factor), osteoarthritis, prior joint injury, metabolic conditions (hyperparathyroidism, hypomagnesaemia, haemochromatosis, hypophosphatasia, Wilson disease), and familial/hereditary CPPD (younger onset).
Clinical Features
Symptoms
Acute onset of hot, swollen, painful joint — typically the KNEE (most common site)
May also affect wrist, ankle, shoulder, hip, and small joints
Attacks often triggered by intercurrent illness, surgery, or trauma
Fever and systemic upset may occur (mimicking septic arthritis)
Chronic form may mimic RA with persistent joint inflammation
Signs
Acute monoarthritis: warm, swollen, tender, erythematous joint with effusion
Large joint effusion (especially knee)
Cannot clinically distinguish from septic arthritis — always aspirate if septic arthritis is possible
Investigations
First-line
Joint aspirationPositively birefringent rhomboid-shaped crystals under polarised light microscopy. Also send for MC&S to exclude septic arthritis
X-ray of affected jointChondrocalcinosis: linear calcification within articular cartilage (menisci of knee, triangular fibrocartilage of wrist, pubic symphysis)
Second-line
Metabolic screenCalcium, PTH (hyperparathyroidism), magnesium (hypomagnesaemia), ferritin and transferrin saturation (haemochromatosis), phosphate — especially if young onset or recurrent
BloodsFBC, CRP (raised), U&Es, LFTs
Specialist
UltrasoundMay show hyperechoic bands within articular cartilage (distinguishes from gout where crystals deposit on cartilage surface — double contour sign)
1
Acute attack
- Joint aspiration: therapeutic (relieves pressure) and diagnostic
- NSAID (naproxen 500 mg BD) or colchicine 500 mcg BD — similar to gout flare treatment
- Intra-articular corticosteroid injection (triamcinolone) — effective for monoarthritis
- Oral prednisolone 30 mg/day for 5–7 days if NSAID/colchicine contraindicated
- Ice, rest, elevation
2
Long-term management
- No equivalent of allopurinol for pseudogout — no proven disease-modifying therapy for CPPD
- Treat underlying metabolic cause if identified (hyperparathyroidism, haemochromatosis, hypomagnesaemia)
- Low-dose colchicine 500 mcg OD may reduce flare frequency (off-label)
- Manage coexistent OA
Complications
- Recurrent attacks: Common — no disease-modifying therapy available
- Chronic CPPD arthropathy: Progressive joint destruction resembling OA
- Crown dens syndrome: CPPD deposition around the odontoid process — causes acute neck pain and stiffness
- Missed septic arthritis: Clinical presentation overlaps — always aspirate and send for MC&S
UKMLA Exam Tips
- 1Pseudogout = positively birefringent RHOMBOID crystals. Gout = negatively birefringent NEEDLE crystals
- 2Pseudogout typically affects the KNEE in ELDERLY patients. Gout affects the 1st MTP in middle-aged men
- 3Chondrocalcinosis on X-ray (meniscal/cartilage calcification) = classic finding of CPPD
- 4If young patient with pseudogout: screen for hyperparathyroidism, haemochromatosis, hypomagnesaemia, Wilson disease
- 5No allopurinol equivalent for pseudogout — treat acute attacks symptomatically
- 6Triggered by intercurrent illness or surgery — common post-operative cause of acute monoarthritis in elderly
practicetest your knowledge on pseudogoutApply what you've learnt with UKMLA-style questions from the iatroX Q-Bank — musculoskeletal and beyond.
open q-bank