What are the differences between coarse, creaking, snowball, and soft crepitus in terms of clinical presentation and underlying causes?

Crepitus Terminology in Medical Imaging

The terms "snowball" and "soft" crepitus refer to specific MRI lesion patterns in neurological conditions, not joint sounds, while "coarse" and "creaking" crepitus describe audible joint phenomena in musculoskeletal disease.

Snowball Crepitus (MRI Lesion Pattern)

"Snowball" lesions are multifocal, rounded brain lesions centrally located in the corpus callosum that are pathognomonic for Susac syndrome, not a type of joint crepitus. 1

• These appear as discrete, round T2-hyperintense lesions with a characteristic "snowball-like" appearance on MRI 1
• They represent a "red flag" finding that distinguishes Susac syndrome from multiple sclerosis 1
• This terminology has nothing to do with joint examination or audible crepitus

Soft Crepitus (Subcutaneous Emphysema)

"Soft" crepitus refers to the palpable crackling sensation felt over soft tissues when subcutaneous air is present, typically from infection, trauma, or post-surgical complications. 2

• The American College of Radiology identifies soft tissue gas-forming infections as a primary cause of soft crepitus 2
• Palpable crepitus in the absence of recent surgery, trauma, or puncture wound is a reliable indicator of infection requiring urgent evaluation 2
• Gas in deep fascial planes indicates necrotizing fasciitis and requires immediate surgical intervention 2
• CT is the most sensitive modality for detecting the extent and compartmental location of soft tissue gas 2

Coarse Crepitus (Joint Examination Finding)

"Coarse" crepitus describes a loud, grinding, or crackling sound during joint movement that is both audible and palpable, most commonly associated with advanced osteoarthritis. 3, 4, 5

• Coarse crepitus in knee osteoarthritis is associated with osteophytes at the patellofemoral and lateral tibiofemoral joints 3
• The pooled prevalence of knee crepitus in osteoarthritis is 81%, compared to 36% in pain-free persons 5
• Coarse crepitus carries a more than threefold increased odds of radiographic OA diagnosis (OR 3.79,95% CI 1.99 to 7.24) 5
• Frequent crepitus predicts incident symptomatic knee OA with adjusted odds ratios increasing from 1.5 (rarely) to 3.0 (always) based on frequency 6

Creaking Crepitus (Joint Examination Finding)

"Creaking" crepitus describes a higher-pitched, squeaking sound during joint movement, often associated with early cartilage changes or scapulothoracic disorders. 7

• Scapulothoracic creaking crepitus produces a grinding or snapping noise with scapular motion and may be accompanied by pain 7
• This type may be due to pathologic changes in bone or soft tissue between the scapula and chest wall 7
• When soft-tissue lesions cause scapulothoracic creaking, conservative treatment with postural and scapular strengthening exercises is highly effective 7

Clinical Implications and Pitfalls

The presence of crepitus should be interpreted in context with functional limitations and pain rather than as an isolated finding. 8, 4

• Individuals with knee crepitus have 3-11% lower self-reported function and quality of life, but no difference in objective function tests 4
• The American College of Radiology recommends focusing on functional limitations rather than crepitus alone in elderly patients 8
• Overreacting to crepitus without considering functional status can lead to unnecessary imaging and interventions 8
• Meniscal tears are often incidental findings in older patients, with the majority over 70 having asymptomatic tears 8

Common pitfall: Confusing imaging terminology ("snowball" lesions) with physical examination findings (audible/palpable crepitus) leads to diagnostic errors and inappropriate management.