Crepitus

Crepitus (/ˈkrɛpɪtəs/; also termed crepitation) is a medical term to describe the grating, crackling or popping sounds and sensations experienced under the skin and joints or a crackling sensation due to the presence of air in the subcutaneous tissue.

Various types of crepitus that can be heard in joint pathologies are:

• Bone crepitus: This can be heard when two fragments of a fracture are moved against each other.
• Joint crepitus: This can be obtained when the affected joint is passively moved with one hand, while the other hand is placed on the joint to feel the crepitus.
• Crepitus of bursitis: This is heard when the fluid in the bursa contains small, loose fibrinous particles.
• Crepitus of tenosynovitis

Causes

The sound can be created when two rough surfaces in an organism's body come into contact—for example, in osteoarthritis or rheumatoid arthritis when the cartilage around joints erodes and the surfaces in the joint grind against one another, or when the fractured surfaces of two broken bones rub together. Crepitus is a common sign of bone fracture.

Crepitus can easily be created and observed by exerting a small amount of force on a joint, thus 'cracking it'. This is caused by bubbles of nitrogen forming in the synovial fluid bursting. Almost every joint in the body can be 'cracked' in this way, but the joints which require the least amount of effort include the hallux, knuckles and neck joints.

In soft tissues, crepitus can be produced when gas is introduced into an area where it is normally not present.

The term can also be used when describing the sounds produced by lung conditions such as interstitial lung disease—these are also referred to as "rales". Crepitus is often loud enough to be heard by the human ear, although a stethoscope may be needed to detect instances caused by respiratory diseases.

In times of poor surgical practice, post-surgical complications involved anaerobic infection by Clostridium perfringens strains, which can cause gas gangrene in tissues, also giving rise to crepitus.

Subcutaneous crepitus (or surgical emphysema) is a crackling sound resulting from subcutaneous emphysema, or air trapped in the subcutaneous tissues.

See also

Look up crepitus in Wiktionary, the free dictionary.

• Cracking joints
• Screamer, a bird whose flesh is filled with crackling gas bubbles

Further reading

• Richards RR, McKee MD (October 1989). "Treatment of painful scapulothoracic crepitus by resection of the superomedial angle of the scapula. A report of three cases". Clinical Orthopaedics and Related Research (247): 111–6. PMID 2791379. doi:10.1097/00003086-198910000-00019. 
• Jiang CC, Liu YJ, Yip KM, Wu E (1993). "Physiological patellofemoral crepitus in knee joint disorders". Bulletin. 53 (4): 22–6. PMID 8829591. 
• Kuhn JE, Plancher KD, Hawkins RJ (1998). "Symptomatic scapulothoracic crepitus and bursitis". The Journal of the American Academy of Orthopaedic Surgeons. 6 (5): 267–73. PMID 9753753. 
• Dennis DA, Kim RH, Johnson DR, Springer BD, Fehring TK, Sharma A (January 2011). "The John Insall Award: control-matched evaluation of painful patellar Crepitus after total knee arthroplasty". Clinical Orthopaedics and Related Research. 469 (1): 10–7. PMC 3008897 . PMID 20706813. doi:10.1007/s11999-010-1485-3. 
• O'Connor, Anahad (December 15, 2014). "Why Do My Knees Make Noise When I Squat?". Ask Well. The New York Times.