Makindo Medical Notes

💎 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.