What Causes Crepitus?
Crepitus occurs due to mechanical friction between joint surfaces, structural pathology within joints (particularly osteophytes and meniscal tears), or the presence of gas in soft tissues from infection or trauma.
Joint-Related Crepitus
Knee Crepitus Mechanisms
The primary structural causes of knee crepitus include:
- Osteophytes (bone spurs) are the most consistently associated structural finding, particularly at the patellofemoral and lateral tibiofemoral compartments 1
- Meniscal tears show the strongest association with general knee crepitus across the entire joint 1
- Cartilage damage paradoxically shows a negative association with crepitus at the medial tibiofemoral compartment, suggesting the grinding sound requires some preserved cartilage surface for friction 1
- Medial collateral ligament pathology contributes to crepitus at the medial compartment 1
Prevalence Context
Crepitus is extremely common and does not necessarily indicate serious pathology:
- 41% of the general population experiences knee crepitus 2
- 36% of pain-free individuals have knee crepitus, demonstrating it can be a benign finding 2
- 81% of those with osteoarthritis experience crepitus, representing a more than threefold increased odds (OR 3.79) of radiographic OA diagnosis 2
The sound represents mechanical grinding between joint surfaces when structural changes create irregular contact patterns during movement 1, 2.
Soft Tissue Crepitus (Subcutaneous Emphysema)
Sternum and Chest Wall
The American College of Radiology identifies distinct pathologic causes:
- Sternal osteomyelitis creates crepitus from bone destruction and associated gas formation 3
- Post-sternotomy complications including sternal dehiscence or nonunion (gap >3mm) produce mechanical crepitus from bone instability 3
- Gas-forming soft tissue infections (necrotizing fasciitis) create palpable crepitus from subcutaneous gas—this is a reliable indicator of infection in the absence of recent trauma or puncture wound 3, 4
- Subcutaneous emphysema from trauma or pneumothorax causes air to track through tissue planes 3
Critical pitfall: Crepitus without recent surgery, trauma, or puncture wound should raise immediate concern for infection requiring urgent evaluation 4.
Scapulothoracic Region
- Bone or soft tissue pathology between the scapula and chest wall creates grinding sounds with shoulder movement 5
- Scapulothoracic bursitis produces both crepitus and pain from inflamed bursae 5
- Altered scapulothoracic congruence from scoliosis or thoracic kyphosis changes the articulation mechanics 5
Clinical Significance
When to Be Concerned
The presence of crepitus alone has limited clinical significance:
- Individuals with knee crepitus show only slightly lower self-reported function (small effect size 0.17-0.41) compared to those without crepitus 6
- No difference in objective function (20-m walk test, chair-stand test) or knee strength exists between those with and without crepitus 6
- Most people with crepitus do not cease exercise, though some modify movements 7
Red Flags Requiring Urgent Evaluation
- Soft tissue crepitus without trauma history indicates gas-forming infection 3, 4
- Crepitus with systemic signs (fever, elevated inflammatory markers) suggests infection 3
- Post-surgical sternal crepitus may indicate dehiscence or osteomyelitis 3
Diagnostic Approach for Pathologic Crepitus
When infection or serious pathology is suspected: