What are the differential diagnoses and treatment options for elbow swelling?

Differential Diagnoses for Elbow Swelling

Elbow swelling requires systematic evaluation starting with plain radiographs to differentiate between infectious, inflammatory, traumatic, and neoplastic etiologies, with the most critical distinction being septic arthritis versus other causes due to implications for urgent treatment. 1

Key Differential Diagnoses

Infectious Causes

• Septic arthritis: Joint effusion with systemic signs of infection, requires urgent aspiration and culture 1
• Soft tissue infection/cellulitis: Effacement of fat planes, soft tissue swelling without intra-articular involvement 1
• Osteomyelitis: Periosteal reaction and erosions in acute cases (<14 days may show only soft tissue swelling); bone sclerosis in chronic cases 1
• Tuberculous arthritis: Rare but presents with chronic swelling, may mimic septic arthritis initially 2, 3

Inflammatory/Rheumatologic Causes

• Rheumatoid arthritis: Synovitis with joint effusion; clinical examination shows only fair agreement with ultrasound findings (kappa 0.371) 4
• Olecranon bursitis: Localized posterior elbow swelling
• Medial or lateral epicondylitis: Soft tissue swelling with tendon pathology 5, 6
• MTX-related lymphoproliferative disorder: Consider in RA patients on methotrexate presenting with severe joint swelling 7

Traumatic Causes

• Fractures: Radial head, olecranon, coronoid process, or epicondylar fractures with associated soft tissue swelling 1
• Ligament/tendon injuries: UCL tears, lateral collateral complex injuries with joint effusion 1, 8
• Elbow dislocation: Associated with ligamentous disruption and significant swelling 1

Other Causes

• Osteochondral defects: Particularly in adolescent athletes; chronic swelling should raise suspicion 9
• Intra-articular loose bodies: May cause mechanical symptoms with intermittent swelling 1
• Heterotopic ossification: Can present with swelling and limited range of motion 1
• Pigmented villonodular synovitis: Rare cause of chronic swelling 3
• Hemophilic arthropathy: In patients with bleeding disorders 3
• Tumors: Must be excluded with initial imaging 1

Diagnostic Approach

Initial Evaluation

• Plain radiographs are mandatory first-line imaging to exclude fractures, tumors, intra-articular bodies, heterotopic ossification, osteochondral lesions, and soft tissue calcification 1
• Look for joint effusion, soft tissue swelling, ulcers, effacement of fat planes, gas, and foreign bodies 1
• Comparison views with the contralateral elbow are often useful 1, 8

When Radiographs Are Normal or Nonspecific

For suspected septic arthritis or soft tissue infection:

• Image-guided aspiration is essential when imaging cannot distinguish infected from noninfected fluid collections; culture identifies the organism and directly affects treatment 1
• CT with IV contrast can assess soft tissue extent and differentiate cellulitis, myositis, tenosynovitis, abscess, and septic arthritis 1
• Ultrasound may improve diagnostic accuracy for effusion detection compared to clinical examination alone 4

For suspected tendon/ligament injury:

• MRI without IV contrast is appropriate for evaluating UCL injuries, lateral collateral complex injuries, and tendinous pathology 1, 6
• MRI has high inter- and intraobserver reliability for epicondylalgia, showing intermediate to high T2 signal within tendons and paratendinous edema 6

For suspected intra-articular pathology:

• MRI or MR arthrography for loose bodies (sensitivity 100%, specificity 67% for MR arthrography), osteochondral lesion stability, and synovial abnormalities 1
• CT or CT arthrography for heterotopic ossification and loose bodies (sensitivity 93%, specificity 66%) 1

Treatment Approach by Etiology

Septic Arthritis (URGENT)

• Immediate arthrocentesis with culture 1
• Empiric antibiotics after culture obtained
• Surgical debridement if indicated

Inflammatory Conditions

• NSAIDs for pain relief 5, 8
• Rest and activity modification: Avoid repetitive wrist flexion and forearm pronation for medial epicondylitis 5
• Cold therapy: 20-30 minutes, 3-4 times daily (avoid direct ice contact with skin) 8
• Functional rehabilitation preferred over immobilization for sprains 8
• Corticosteroid injections for persistent symptoms despite first-line treatment, though use with caution due to potential complications 5, 8

Traumatic Injuries

• Compression wrap for comfort without compromising circulation 8
• Semirigid supports superior to elastic bandages for protection 8
• Progressive strengthening exercises after acute phase 8
• Surgical consultation for refractory cases or unstable fractures 1, 8

Critical Pitfalls to Avoid

• Chronic swelling in adolescent athletes warrants investigation for osteochondral defects, even when soft tissue injury seems apparent 9
• Do not rely solely on clinical examination for detecting joint effusion in RA patients; ultrasound significantly improves accuracy 4
• Consider tuberculous arthritis in patients not improving with standard septic arthritis treatment 2, 3
• MTX-LPD should be in the differential when RA patients on methotrexate develop severe joint swelling 7
• Overreliance on corticosteroid injections without addressing underlying biomechanical issues is a common management error 5