Makindo Medical Notes

Milwaukee shoulder is a rare and severe form of shoulder arthropathy caused by the deposition of hydroxyapatite crystals. The definitive diagnosis is made through identifying these crystals in the synovial fluid.

About Milwaukee Shoulder

• A rare condition characterized by rapid and progressive destruction of the shoulder joint due to hydroxyapatite crystal deposition.
• Primarily affects the shoulder, often leading to significant joint degeneration and disability.

Pathophysiology

• Caused by the extensive deposition of basic calcium phosphate (BCP) crystals, including hydroxyapatite, in large joints.
• The accumulation of these crystals activates enzymes like collagenase, which degrade cartilage and accelerate joint destruction.
• This process leads to more rapid joint degeneration compared to typical osteoarthritis.

Clinical Features

• Gradual onset of shoulder pain, which may be triggered or worsened by minor injuries or overuse.
• More common in women, especially post-menopausal women.
• Symptoms include severe pain, significant joint dysfunction, and progressive destruction of the shoulder joint.
• Patients may also experience reduced range of motion, swelling, and visible deformities in the shoulder.

Key Differential Diagnoses

• End-stage avascular necrosis (AVN)
• Chronic septic arthritis
• Neuropathic (Charcot) joint

Investigations

• X-rays: Show joint space narrowing, osteophyte formation, and soft tissue calcifications.
• Joint Aspiration: Non-inflammatory synovial fluid analysis reveals the presence of BCP crystals, cartilage fragments, and often large crystal aggregates.
• Blood Tests: Full blood count (FBC), urea & electrolytes (U&E), liver function tests (LFT), and C-reactive protein (CRP) are usually normal, ruling out infection.
• Synovial Fluid Culture: Typically negative, supporting a non-infectious cause of the joint damage.

Management

• Analgesics: NSAIDs or other pain relievers to manage pain and inflammation.
• Intra-articular Glucocorticoid Injections: Temporarily reduce inflammation and alleviate pain.
• Physical Therapy: Helps to maintain joint mobility and function, reducing long-term disability.
• Surgery: In severe cases, joint replacement may be necessary due to extensive joint damage from crystal deposition.