Milwaukee shoulder syndrome
💎 Milwaukee Shoulder is a rare, destructive shoulder arthropathy caused by deposition of hydroxyapatite crystals.
✅ The definitive diagnosis is made by identifying these crystals in synovial fluid.
It is often under-recognised and can mimic end-stage arthritis or infection.
📖 About Milwaukee Shoulder
- Rare, rapidly progressive destruction of the glenohumeral joint due to basic calcium phosphate (BCP) crystal deposition (not urate like gout, nor CPPD like pseudogout).
- Most commonly affects the shoulder, though knee and hip may occasionally be involved.
- Often leads to significant disability, especially in older women.
🧪 Pathophysiology
- BCP crystals (mainly hydroxyapatite) accumulate in periarticular tissues and synovial fluid.
- These crystals activate proteolytic enzymes (e.g., collagenase, protease) that destroy articular cartilage and surrounding structures.
- Progression is much more rapid than typical osteoarthritis ➝ “destructive arthropathy”.
🩺 Clinical Features
- Gradual, insidious onset shoulder pain ➝ worsens after minor trauma or repetitive use.
- Marked joint dysfunction with stiffness, swelling, and often effusion containing debris (“rice bodies”).
- Classically seen in elderly women (post-menopausal).
- Loss of active movement is profound, but pain may paradoxically reduce in late disease due to joint destruction.
- Gross deformity of the shoulder in advanced cases.
🔍 Key Differential Diagnoses
- 🦴 End-stage avascular necrosis (AVN)
- 🦠 Chronic septic arthritis
- 🧠 Neuropathic (Charcot) joint (esp. in diabetes)
🧾 Investigations
- 🩻 X-rays: Rapid joint space loss, osteolysis, fragmentation, soft tissue calcification, “disappearing shoulder”.
- 💉 Joint aspiration: Non-inflammatory synovial fluid with hydroxyapatite crystals (require special stains/electron microscopy; not birefringent like gout/CPPD).
- 🧪 Bloods: FBC, U&E, LFTs, CRP usually normal ➝ helps rule out infection.
- 🧫 Culture: Negative, confirming non-infective cause.
⚕️ Management
- 💊 Analgesics: NSAIDs or paracetamol to control pain.
- 💉 Intra-articular steroids: Short-term relief of inflammation and pain.
- 🏋️ Physical therapy: Maintain range of motion, prevent contractures, preserve function.
- 🦾 Surgery: Severe cases often require joint replacement due to massive bone and cartilage destruction.
🌟 Key Point
Unlike gout (urate) and pseudogout (CPPD), Milwaukee Shoulder is due to hydroxyapatite crystals.
Diagnosis is frequently delayed because crystals are small and non-birefringent ➝ electron microscopy or special stains are needed.
Always consider in an elderly woman with rapid shoulder destruction but normal inflammatory markers.
