What is the differential diagnosis and recommended evaluation and management for a left sternoclavicular (SC) joint that appears more prominent and produces crepitus?

Prominent Left Sternoclavicular Joint with Crepitus: Differential Diagnosis and Management

The most likely diagnosis is degenerative osteoarthritis of the sternoclavicular joint, which should be initially evaluated with plain radiographs followed by CT if radiographs are inconclusive, while maintaining vigilance for inflammatory arthropathies and infection based on clinical context. 1, 2

Differential Diagnosis

The prominent left SC joint with crepitus has several potential etiologies that must be systematically considered:

Most Common: Degenerative Osteoarthritis

• Osteoarthritis is the most frequent cause of SC joint swelling and crepitus, particularly in patients over age 40, with 53% of individuals over 60 showing moderate to severe radiographic changes. 3, 4
• Degenerative changes typically affect the inferior portion of the clavicular head and may be bilateral with mild asymmetry. 4
• Crepitus results from cartilage loss, subchondral sclerosis, and osteophyte formation. 5, 4
• Female gender and presence of subchondral cysts on CT are significantly associated with degenerative disease. 6

Inflammatory Arthropathies (Critical Not to Miss)

• Spondyloarthritis and SAPHO syndrome frequently involve the SC joint and present with pain, often bilaterally. 7, 1, 8
• Bone scintigraphy demonstrates 100% sensitivity for detecting SC joint inflammation in patients with spondyloarthritis presenting with anterior chest wall pain. 7, 1, 8
• CT findings in inflammatory arthritis include erosions (44%), sclerosis (77.3%), and hyperostosis (41%). 7, 1
• Look for associated features: inflammatory back pain, psoriasis, HLA-B27 positivity, or other joint involvement. 2

Septic Arthritis (Must Rule Out)

• Joint capsule distention ≥10 mm extending over both clavicle and sternum is highly suggestive of infection. 6
• Additional red flags include: elevated ESR, fever, bone marrow edema on MRI, and unilateral presentation. 6
• Average joint distention with infection is 14 mm (range 10-20 mm) versus 5 mm (range 3-8 mm) with degeneration. 6

Other Considerations

• Primary bone/cartilage tumors and metastases can present similarly and must be excluded. 3
• Chronic non-bacterial osteitis (CNO) should be considered if bone marrow edema is present on MRI. 2

Recommended Evaluation Algorithm

Step 1: Clinical Assessment

Evaluate for:

• Fever, elevated inflammatory markers (ESR, CRP), and systemic symptoms suggesting infection. 6
• Inflammatory back pain, psoriasis, or other joint involvement suggesting spondyloarthritis. 2
• Age and gender: degenerative disease more common in older patients and females. 6, 4
• Degree of joint swelling and tenderness: marked distention suggests infection. 6

Step 2: Initial Imaging - Plain Radiographs

• Start with conventional radiography (plain X-rays) of the SC joints as the first-line imaging modality. 1, 2
• Look for: joint space narrowing, osteophytes, subchondral sclerosis, and cysts characteristic of osteoarthritis. 4
• Radiographs have limited sensitivity for early changes and soft tissue pathology. 2

Step 3: Advanced Imaging - CT Chest

• Proceed to CT when plain radiographs are inconclusive or fail to demonstrate expected pathology. 1
• CT provides superior characterization of osseous involvement, cortical erosion, and disease extent. 7, 2
• CT shows higher sensitivity (92.3%) and specificity (64.3%) for differentiating tumors from inflammatory conditions. 7
• Subchondral cysts on CT favor degenerative disease over infection. 6

Step 4: MRI (When Indicated)

• Consider MRI when soft tissue characterization is needed or to detect early inflammatory changes. 1
• MRI is superior for detecting bone marrow edema, which suggests inflammatory or infectious processes. 7, 2, 6
• Bone marrow fluid signal on MRI is significantly associated with infection. 6
• MRI has 62.5% sensitivity for detecting SC joint involvement in spondyloarthritis. 7

Step 5: Nuclear Medicine (Selective Use)

• Bone scintigraphy should be considered only when other imaging is negative but inflammatory arthritis is strongly suspected. 1
• 100% sensitivity for detecting SC joint inflammation in spondyloarthritis, but lacks specificity. 7, 1

Management Approach

For Degenerative Osteoarthritis (Most Likely)

• Conservative management is first-line: activity modification, NSAIDs, and physical therapy. 5, 9
• Corticosteroid injections may be considered for refractory cases. 8, 9
• Joint resection reserved for persistent symptoms unresponsive to conservative treatment. 5

For Inflammatory Arthropathies

• NSAIDs remain first-line pharmacologic therapy for CNO or SAPHO syndrome. 2, 8
• Systemic therapies (bisphosphonates or biologics) may be considered for progressive symptomatic disease. 2
• Avoid overlooking systemic inflammatory conditions that may require disease-modifying treatment. 2

For Suspected Infection

• Joint aspiration or biopsy is mandatory when infection cannot be excluded by imaging. 2, 3
• Empiric antibiotics should not be started until cultures are obtained unless patient is septic. 6

Critical Pitfalls to Avoid

• Do not dismiss SC joint swelling as purely degenerative without thorough evaluation, as serious conditions like septic arthritis or neoplasia may present similarly. 3
• Do not perform routine bone biopsy unless there is concern for infection or malignancy that cannot be excluded by imaging. 2
• Do not use systemic corticosteroids for isolated SC joint pathology without establishing the diagnosis, as this could worsen infection. 8
• Do not overlook bilateral involvement or systemic symptoms that suggest inflammatory arthropathy requiring different management. 2, 8