A high-yield, exam-focused clinical summary for diagnosing and managing CPPD crystal arthritis in the AMC MCQ.
3/2/2026 · 6 min read
Tags: PSEUDOGOUT, CPPD, RHEUMATOLOGY, HIGH YIELD, CLINICAL GUIDE
Note: This article is an educational resource for AMC MCQ preparation and does not replace clinical judgement or local specialist advice.
1. The Basics
Pseudogout is an acute inflammatory arthritis caused by calcium pyrophosphate dihydrate (CPPD) crystal deposition.
- Classic Patient: Older adult (>60 years).
- Classic Joint: Knee (>50% of cases), followed by the wrist and ankle.
- Classic X-ray Finding: Chondrocalcinosis (linear calcification in the cartilage/menisci).
2. Presentation & Diagnosis (The "AMC Step-by-Step")
Important AMC Rule: A hot, swollen, acutely painful joint is Septic Arthritis until proven otherwise.
Step 1: Joint Aspiration (The most important first step)
You must aspirate the joint before giving intra-articular steroids or assuming it is just a flare.
- Crystals: Rhomboid-shaped (or rod-shaped), weakly positively birefringent. Under polarized light, they appear blue when parallel.
- WCC (White Cell Count): Inflammatory range (2,000 - 50,000 cells/µL), mostly neutrophils.
- Gram Stain/Culture: Negative (unless co-infection is present).
Step 2: Imaging (Ancillary test)
X-Ray: Look for chondrocalcinosis (calcification of the knee menisci, triangular fibrocartilage of the wrist, or pubic symphysis).
Note: A normal X-ray does not rule out pseudogout.
3. Secondary Causes (When to investigate?)
If a patient is young (<55 years) or has recurrent/atypical polyarticular flares, the AMC expects you to screen for metabolic triggers.
Remember the "H"s:
- Haemochromatosis (Screen with Iron studies / ferritin)
- Hyperparathyroidism (Screen with Calcium, PO4, PTH)
- Hypomagnesaemia (Screen with Magnesium)
- Hypothyroidism (Screen with TSH)
- Hypophosphatasia (Screen with ALP - characteristically low)
4. High-Yield Differential Diagnosis
| Feature | Pseudogout (CPPD) | Gout | Septic Arthritis | Osteoarthritis | |---|---|---|---|---| | Typical Joint | Large joints (Knee, Wrist) | 1st MTP (Podagra), Foot | Single large joint (Knee) | Weight-bearing (Knee/Hip), Hands | | Patient Profile | Elderly (>60), OA history | Middle-aged men, Metabolic syndrome | Immunosuppressed, post-op, prosthetic joint | Elderly with chronic pain | | Crystals | Rhomboid, weakly positive | Needle, strongly negative | None (but can coexist with crystals) | None | | WCC (Synovial) | 2,000 - 50,000 | 2,000 - 50,000 | >50,000 | <2,000 (Non-inflammatory) | | X-Ray / Imaging | Chondrocalcinosis | Erosions with overhanging edges ("rat bite") | Normal early, destructive later | Joint space narrowing, osteophytes |
5. Acute Management
Always rule out septic arthritis first. Treatment depends on the number of joints and the patient's medical history (renal, GI, cardiac).
1st Line Options:
Intra-articular (IA) Corticosteroids (e.g., cortisone injection)
- Best for: 1-2 affected joints.
- Why? Rapid relief, avoids systemic side effects (especially important in elderly patients with CKD, HF, or peptic ulcers).
- Prerequisite: Infection must be excluded via aspiration.
NSAIDs (e.g., Ibuprofen, Indometacin)
- Best for: Polyarticular flares or patients refusing injection.
- Avoid in: Chronic Kidney Disease (CKD), Heart Failure, Peptic Ulcer Disease, elderly/frail patients, patients on anticoagulants.
Colchicine
- Best for: Systemic alternative to NSAIDs, provided it can be given early (ideally within 12-24 hours of flare onset; efficacy drops significantly after 36 hours).
- Avoid in: Severe renal impairment (eGFR <10), or patients taking strong CYP3A4 inhibitors (e.g., clarithromycin).
- Dose reduction required: Moderate-to-severe renal impairment (eGFR <50). Do not use standard dosing.
2nd Line (Systemic):
Oral Corticosteroids (e.g., Prednisolone)
- Best for: Polyarticular flare where NSAIDs and Colchicine are contraindicated (e.g., CKD patient with peptic ulcer).
- Caution: Uncontrolled diabetes, existing infection.
Unlike Gout (where Allopurinol is used), there is no specific urate-lowering or crystal-depleting therapy for CPPD. Long-term management involves optimizing secondary causes, weight loss, and rarely, prophylactic low-dose colchicine.
6. AMC MCQ Practice Cases
Case 1: The Classic Presentation & Next Step
Scenario: A 75-year-old male is 3 days post-total hip replacement. He develops a sudden, hot, swollen right knee and a fever of 38.4°C. X-ray shows linear calcific densities in the meniscus. What is the most important next step?
Correct Answer: Joint aspiration for microscopy and culture.
Explanation: Despite the classic X-ray finding of chondrocalcinosis, a hot swollen joint in a post-op patient is septic arthritis until proven otherwise. You must aspirate before injecting steroids.
Case 2: The Younger Patient
Scenario: A 45-year-old male presents with recurrent episodes of red, hot, swollen knees and wrists. Joint aspiration confirms rhomboid, positively birefringent crystals. His magnesium and TSH are normal. What other investigations are indicated?
Correct Answer: Iron studies and Serum Calcium / PTH.
Explanation: CPPD in a patient <55 years old should prompt investigation for secondary causes like Haemochromatosis (Iron studies) and Hyperparathyroidism (Ca/PTH).
Case 3: Choosing the Right Treatment
Scenario: An 82-year-old female presents with an acute afebrile flare of pseudogout in her left knee, confirmed by aspiration (Gram stain negative). She has Stage 4 Chronic Kidney Disease (eGFR 22 mL/min) and a past history of a bleeding gastric ulcer. What is the best treatment?
Correct Answer: Intra-articular corticosteroid injection.
Explanation: The patient has isolated monoarthritis. NSAIDs are absolutely contraindicated due to CKD and ulcer history. Colchicine is inappropriate at eGFR <30. IA steroids are the safest and most effective choice here.
Case 4: Polyarticular Flare with Comorbidities
Scenario: A 70-year-old male presents with acute pain and swelling in both knees and his right wrist. Aspiration of the knee shows CPPD crystals and negative culture. He has a history of congestive heart failure and chronic kidney disease (eGFR 40 mL/min). What is the preferred systemic treatment?
Correct Answer: Oral prednisolone (short course) OR dose-adjusted colchicine.
Explanation: NSAIDs are contraindicated due to heart failure (fluid retention) and CKD. Because multiple joints are involved, IA injections might be less practical. A short course of oral corticosteroids (or carefully dose-adjusted colchicine) is preferred.
Case 5: Long-Term Management & The "Gout Trap"
Scenario: A 72-year-old male with recurrent pseudogout flares presents for long-term management advice. His recent flares have been debilitating. He asks if there is a medication to "lower his crystal levels" like his brother takes for gout. What is the most appropriate long-term management strategy?
Correct Answer: Lifestyle modification and prophylactic low-dose colchicine.
Explanation: This is a very common exam trap. Unlike gout, there is no urate-lowering or crystal-depleting therapy (like Allopurinol) for CPPD. Long-term management focuses on reducing flare frequency with prophylactic low-dose colchicine (dose-adjusted for renal function if needed) and optimizing joint biomechanics (weight loss, physiotherapy).
7. References
- EULAR Recommendations for Calcium Pyrophosphate Deposition: Part II - Management (2011)
- Medicine Today - Crystal arthritis: Managing gout and calcium pyrophosphate deposition disease (2024)
- RACGP - My knee is swollen (2008)
- UCSF Hospital Handbook - Gout and Pseudogout
- UpToDate - Gout: Treatment of Flares (2025)
- Arthritis Australia - Gout
- Arthritis Australia - Osteoarthritis
- Arthritis Australia - Colchicine
- Rheumatology Australia - Allopurinol
- Rheumatology Australia - Colchicine
- Safer Care Victoria - Gout and Pseudogout (2019)
- Medcast - Gout: Clinical Essentials and MCQ
- Medcast - Gout Treatment Algorithm
- Medical Republic - Treating Pseudo-Pseudogout (2022)
- NPS - Management of acute gout (2004)
- RACGP - The Management of Gout: Much Has Changed (2016)
- Australian Prescriber - The Management of Gout (2016)
- Pharmaceutical Society of Australia - Gout Quick Reference Guide (2024)