What Is Crepitus?

What Crackling Sounds in the Joints or Lungs Mean

Knee pain and crepitus
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Crepitus is the abnormal popping or crackling sound in either a joint or the lungs, which may be faint or loud enough for people to hear. It is often accompanied by a popping or crunching sensation that may sometimes be uncomfortable or painful. Crepitus in the joints is typically related to joint damage or the formation of tiny bubbles in the fluids surrounding the joint. Crepitus in the lungs is caused when the air sacs abruptly collapse as the lungs fill with fluid.

Crepitus is not so much a condition but rather a descriptive characteristic that doctors use to pinpoint the source of the problem. The term "crepitus" is derived from the Latin for "rattling" or "creaking."

Crepitus of the Joints

Crepitus may occur in tandem with a joint disorder or entirely on its own. As a symptom, it is not inherently problematic. Cracking your knuckles, for example, is a form of crepitus wherein tiny nitrogen bubbles in a joint suddenly pop with strenuous movement.

It is generally only a problem when the popping is progressive or is accompanied by symptoms of joint damage, injury, or infection.

Joint Damage

Crepitation can occur when the roughened surfaces of two joints rub together, causing the physical grating of cartilage and/or bone. This can occur when the meniscus (the fibrous cartilage between the surfaces of joints) is gradually worn down or damaged. Repetitive stress can cause cartilage fibers to fray or form tiny crevasses. As the joint moves, these crevasses can "catch" and create popping sounds, often without causing pain.

If pain is felt, it is typically related to advanced joint damage and/or the compression of nerves between narrowed joint spaces. It is at this stage that the joint may begin show signs of injury, including swelling, redness, reduced range of movement, and malformation.

Osteoarthritis ("wear-and-tear arthritis") is the most common cause of this, although crepitus can occur with other forms of arthritis, including rheumatoid arthritis, psoriatic arthritis, gout, and juvenile idiopathic arthritis. It can affect any joint of the body but is most common in the knees, hands, feet, lower back, hips, and shoulders.

Joint Inflammation or Injury

Crepitus can also occur when a facet of the joint is inflamed or injured, which can happen with conditions such as the following. These types of disorders are usually accompanied by pain and the marked restriction of movement.

  • Bursitis: This is inflammation of the fluid-filled sacs in the joint space called bursa. It may be caused by an infection, autoimmune disorder, trauma, or a repetitive use injury. Crepitus is often detected when the inflammation starts to subside and portions of the distended sac get trapped during movement, causing a popping sound.
  • Tenosynovitis: With this, inflammation builds up in the fluid-filled sheath called the synovium, which surrounds a joint tendon. Tiny bubbles can form in the synovial fluid, which pops whenever the joint is moved.
  • Patellofemoral pain syndrome (PFPS): Also known as runner's knee, this is caused when the cartilage under the kneecap (patella) is damaged. Crepitus is a common feature of PFPS since fragments of ruptured cartilage scrape together during movement.
  • Temporomandibular joint disorders (TMJ), which are characterized by severe bouts of radiating nerve pain in the jaw (mandible), often cause crepitus because of displacement of the cartilage disc in the hollow (fossa) where the jaw is articulated. This can result in both a clicking sound and popping sensation as you open your mouth.

    Almost any injury of the joint cartilage can cause clicking or popping sounds as the uneven surfaces rub together. Rotator cuff tears and triangular fibrocartilage complex (TFCC) of the wrist are two such examples. Even abnormally shaped cartilage, such as with discoid lateral meniscus (misshapen disc in the knee), can trigger this effect.

    A less common cause of crepitus is scleroderma, a rare disorder characterized by the hardening and tightening of the skin and connective tissues. When this happens, it can cause coarse creaking sounds and sensations as the shortened tendons scrape against bone and cartilage.

    Crepitus of the Lungs

    While we typically apply the term "crepitus" to the joints, it can also be used to describe audible crackling sounds in the lungs. Also referred to as bibasilar crackles or rales, the sounds are related to the excessive accumulation of fluids in the lungs, most often as a result of infection, poor circulation, or lung disease.

    The causes for rales remain more or less the same irrespective of the underlying condition. As fluids accumulate, they cause the tiny air sacs in the lungs (called alveoli) to collapse. As you inhale, the alveoli will expand, albeit with difficulty. As you exhale, the sacs with snap back into their collapsed state, causing the characteristic cracking sound.

    Among some of the conditions for which rales are common:

    Crepitus of the lungs can usually be detected with a stethoscope but may sometimes be loud enough to be heard unassisted.

    Diagnosis and Treatment

    If crepitus is detected, the diagnostic process can vary depending on the location the sounds are coming from, the severity, and accompanying symptoms.

    Joint Disorders

    In some cases, the popping of a joint may be more irritating than problematic and, as such, may not warrant investigation or treatment. If there is pain, inflammation, or restriction of motion, your doctor may order tests to pinpoint the cause. These may include:

    • Imaging tests such as ultrasound, X-ray, or computed tomography (CT) to detect bone or joint injury, or magnetic resonance imaging (MRI) to detect soft tissue damage
    • Blood tests to check for infection or inflammation
    • Antibodies tests to confirm autoimmune disorders such as rheumatoid arthritis
    • Arthrocentesis in which fluid is extracted from the joint space with a needle for analysis in the lab

    Treatment may involve ice application and non-steroidal anti-inflammatory drugs (NSAIDs) to alleviate mild to moderate inflammation and pain. Severe cases may require splinting or intraarticular steroid injections to help further reduce inflammation.

    Infectious causes of joint inflammation are most often bacterial and may require a short course of antibiotics. Immune suppressive drugs are sometimes used to treat inflammatory autoimmune diseases.

    Severe injuries (such as torn tendons, ligaments, or cartilage) may require surgery, typically performed arthroscopically with keyhole incisions. If your mobility or quality of life is significantly impaired, joint replacement surgery may be considered, accompanied by extensive rehabilitation and physical therapy.

    When you return to routine exercise, modifications such as opting for low-impact activities and using lighter weights can help keep crepitus in check.

    Lung Disorders

    Crepitus of the lungs is never considered normal. Depending on your medical history and accompanying symptoms, the following tests may be ordered:

    The treatment can vary based on whether the condition is acute or chronic.

    Doctors will typically treat bacterial pneumonia or bronchitis with antibiotics. Viral infections may be treated with antiviral drugs but are more often allowed to run their course with bed rest and plenty of fluids.

    Chronic conditions usually require lifestyle changes, including smoking cessation, exercise, and the avoidance of airborne irritants. Conditions like COPD will generally require oral or inhaled corticosteroids and bronchodilators. Pulmonary rehabilitation and oxygen therapy can help prevent disease progression and maintain a quality of life.

    Pulmonary edema may require the aggressive treatment of the underlying heart failure, ranging from chronic medications to bypass surgery. Surgery may be an option for people with advanced lung disease when all other treatments fail. A lung transplant is a last resort for those who lungs are no longer functional.

    A Word From Verywell

    Crepitus may be a sign of a serious illness or mean nothing at all. If uncertain about whether a clicking or crackling sound is problematic, always err on the side of caution and get checked out. If there is pain, swelling, redness, or you are suddenly less able to move a joint, do not hesitate to schedule an appointment with a doctor or orthopedist.

    However, if you ever hear crackling sounds when you breathe, see your doctor as a matter of urgency whether or not there are any other symptoms. The earlier you do so, the more likely you will be to identify and treat the condition before it turns serious.

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    Article Sources
    • Firestein, G.; Budd, R.; O'Dell, J. et al. (2013) Kelley's Textbook of Rheumatology (9th ed). New York, New York: Elsevier. DOI: 10.1016/C2009-1-62542-9.
    • Zander, D. and Farver, C. (2017) Pulmonary Pathology: A Volume in the Series: Foundations in Diagnostic Pathology(2nd ed). New York, New York: Elsevier. ISBN-13:978-0323393089.