What is crepitus, what diseases is this manifestation typical for?

Crepitation, or crunching in the knee joints, is an extremely common phenomenon, occurring in almost 99% of cases. These sounds can cause severe anxiety and give rise to fears that joints are being destroyed, and also affect human behavior. This issue has so far been little studied, but existing research suggests that most knee noises are physiological rather than pathological in nature.

Types of noise

Crepitation in the knees can be divided into pathological and physiological.

Pathological noise

A pathological murmur is usually associated with some specific circumstance or injury. For example, when the anterior cruciate ligament is torn, the knee may make a popping sound, and when the meniscus is torn, the knee will click in certain positions. Pathological crepitus can also be caused by degenerative joint diseases, mediopatellar fold syndrome, patellofemoral instability, and snapping knee syndrome. It can also occur after knee surgery. In these cases, in addition to pathological noise, patients will also have other symptoms: pain, swelling, joint effusion, etc. It is assumed that treatment in the early stages solves the problem of both crepitus and other symptoms.

Physiological noise

Physiological noise, in contrast to pathological noise, is a much more common phenomenon. In 1990, McCoy used vibration arthrography to examine the joints of volunteers and came to the conclusion that 99% of knees produced some kind of sound. At the same time, people who exhibited physiological crepitus often could not accurately describe the sounds made by the knee. They also had no injuries associated with this crunch.

A knee noise is considered physiological if it is not related to pain or decreased function and is simply a sound. Often people consider their crepitus to be an alarm signal and are very worried about it, and, as a rule, they are relieved to learn that there is no talk of any pathology.

Publications in the media

Classification • Fracture of the proximal end •• Intra-articular fracture ••• Fracture of the head ••• Fracture of the anatomical neck •• Extra-articular fracture ••• Fracture of the tubercular region: transtubercular fractures, isolated fractures of the tubercles ••• Fracture of the surgical neck • Fracture of the diaphysis •• Fracture of the upper thirds •• Middle third fracture •• Lower third fracture • Distal end fracture •• Supracondylar fracture •• Condylar fractures ••• Transcondylar ••• Intercondylar (T- and V-shaped) ••• Isolated condylar fractures. Causes • Intra-articular fracture of the proximal end - direct blow to the outer surface of the shoulder joint, fall on the elbow or hand • Fracture of the tubercles of the humerus - excessive muscle contraction (avulsion fracture) • Fracture of the surgical neck - fall on the elbow, abducted arm or shoulder • Fracture of the diaphysis of the shoulder - direct blow, fall on the elbow or straight arm • Fracture of the distal end - fall on the elbow or palm.

Pathomorphology • Fracture of the proximal end - with a fracture of the anatomical neck, the distal fragment is embedded in the head (impacted fracture); with a strong blow, the head of the humerus can be crushed into small fragments. Fracture-dislocations of the humerus often occur • Fracture of the surgical neck - abduction (an angle open outward and posteriorly is formed between the fragments), adduction (angle open inwardly and posteriorly) and impacted fractures are possible • Fractures of the diaphysis of the humerus can be comminuted, transverse, oblique and helical. The displacement of fragments depends on the nature of the injury and muscle traction. Possible injury to the neurovascular bundle (radial nerve) • Supracondylar fractures can be flexion or extension. Extension fractures are often complicated by damage to the neurovascular bundle and soft tissues • Condylar fractures are often combined with a fracture of the olecranon.

Clinical picture • Impacted fracture of the proximal end - no classic signs of fracture (crepitus, pathological mobility, inability to raise the arm). X-ray examination helps in diagnosis. • Fracture of the tuberosities - sharp pain on palpation, rotation of the shoulder inwards (fracture of the greater tuberosity) or outwards (fracture of the lesser tuberosity), lack of active rotation outwards (fracture of the greater tuberosity) or inwards (fracture of the lesser tuberosity). • Surgical neck fracture is a classic fracture presentation. Diagnosis of an impacted fracture is difficult - the function of the limb suffers little, pain is detected on palpation, axial load, and rotation; X-ray examination helps in diagnosis. • Fracture of the diaphysis - swelling, deformation, pathological mobility, dysfunction and shortening of the limb. If the radial nerve is damaged, the clinical picture is paralysis or paresis of the hand. • Supracondylar fractures. With extension fractures, the shoulder is shortened, there is a depression above the olecranon, and the distal end of the central fragment is palpated in the elbow bend. In flexion fractures, the shoulder is elongated, and the end of the central fragment is palpated above the olecranon. The Marx sign is violated - the axis of the shoulder is not perpendicular to the line drawn through the condyles. • Fractures of the condyles - an increase in the volume of the elbow joint, severe pain during rotation of the forearm. • Intercondylar fractures - the elbow joint is increased in volume, active movements are impossible, pathological mobility in the lateral directions.

TREATMENT • Avulsion of the greater tubercle without displacement - bandage for 10-15 days, avulsion with displacement - fixation with a plaster cast for 1.5-2 months after shoulder abduction by 90°, external rotation by 60° and anterior flexion by 30-40° . • Fracture of the surgical neck •• Impacted fracture without displacement or with slight displacement - the arm is bent at the elbow joint 60–70°, suspended on a scarf, placing a roller in the axillary fossa •• Fractures with displacement - skeletal traction, immediate reduction or surgical treatment . A Turner splint is applied. • Fracture of the diaphysis—simultaneous reduction or skeletal traction of the olecranon process weighing 4–5 kg. The shoulder is immobilized in a position of abduction by 90° and brought forward from the frontal plane by 30–40°. The Ilizarov apparatus is also used. In case of a fracture with damage to the radial nerve, conservative treatment is carried out. For fresh closed fractures of the shoulder, accompanied by paresis of the radial nerve, surgery is indicated for displacement of fragments with interposition of soft tissues. • Supracondylar fractures. Reposition of fragments, plaster cast in a position of flexion at the elbow joint at 90–100°, fixation of the forearm in the middle position between pronation and supination. • Condylar fractures. Reposition of fragments, plaster cast for 3 weeks in the position of flexion at the elbow joint at 100–110°, the forearm in the middle position between pronation and supination. • Intercondylar fractures: skeletal traction, V-shaped plaster cast for 3 weeks on the outer-inner surface of the shoulder. If conservative treatment is ineffective, osteosynthesis is performed.

ICD-10 • S42 Fracture at the level of the shoulder girdle and shoulder

Causes of physiological crepitus

The exact reason why a crunch in the knee occurs has not yet been established, but there are several theories about this.

Theories

• Accumulation and rupture of bubbles in synovial fluid (tribonucleation, or cavitation).
• The sound is caused by a tendon or ligament sliding against a bony prominence (usually the biceps femoris muscle at the side of the knee joint).
• Mediopatellar fold syndrome.
• Hypermobility of the meniscus.
• Discoid meniscus.
• The “stick-slip” phenomenon.

Loud creaking and rough sounds produced by a healthy patellofemoral joint are the most common types of crepitus. According to one of the latest theories, the cause of these noises is the “stick-slip” phenomenon in the knee joint. This phenomenon occurs when two surfaces move relative to each other. In this case, the retropatellar cartilage sometimes has an uneven surface (otherwise known as chondromalacia of the patella). It has been suggested that this intermittent movement of the patella along the femur may be the cause of crepitus.

Types of sounds that occur in the knee joint

Types and features

Cracking is a characteristic symptom for several pathological conditions:

• Pulmonary crepitus.

Occurs in the alveoli when they are filled with liquid exudate or transudate. Most often, crackling occurs with pneumonia, tuberculosis, and other inflammatory diseases of the lungs. Heart failure can be identified as a separate cause. Crepitation in the lungs is detected by listening (auscultation) with a deep breath.

• Joint or bone crepitus.

It is observed in bone fractures, when a fragment of one bone rubs against another. Usually there is no auscultation, since a history, examination and x-ray are sufficient to make a diagnosis. But cracking in the joints is an important diagnostic sign for grade 2 arthrosis. It differs from the usual ringing crunch of healthy joints, since the crackling with arthrosis is quiet, hissing.

• Subcutaneous crepitus.

The rarest type of symptom, which is also called subcutaneous emphysema. Occurs when air bubbles enter the subcutaneous tissue. This can be heard with pneumothorax, rib fractures, rupture of the trachea, bronchi, or any other lesion of the respiratory tract with a violation of their integrity. The most rare cause of cracking is anaerobic skin infections.

Relationship between crepitus, pain and movement in patellofemoral pain syndrome

Knee pain! What to do? Diagnostics. Yuri Sdobnikov
More recently, a group of scientists conducted research into crepitus in the knee joint and its relationship with pain and dysfunction. In 2021 De Oliveira et al. recruited 165 women with patellofemoral pain syndrome (PFPS) and 158 women without pain. The researchers assessed existing crepitus and pain in the front of the knee, and then asked participants to do 10 squats and 10 step-ups. The study found that crepitus was more common in women with SPFS (it was detected in 68% of participants with SPFS and in 33% without SPFS). However, no significant correlation was found between existing crepitus and joint function, level of physical activity, pain intensity over the past month, or pain when climbing a step or when squatting.

Also in 2021. De Oliveira et al. conducted another study that examined the association of crepitus with clinical manifestations in women with SPFS and without patellofemoral pain. They found that crepitus was more common in women with this syndrome (50.7% of participants). In women without SPF, crepitus occurred in 33.3% of cases. A study by De Oliveira et al. revealed the following:

• Participants with SPF demonstrated higher levels of kinesiophobia, were more likely to catastrophize pain, and rated their knee function as lower than women without pain. The presence or absence of crepitus had no effect on the indicators described above.
• Participants with SPF (both with and without crepitus) and participants without SPF with crepitus had lower functional capacity than women without crepitus and without pain.

An important conclusion to emerge from this study is that crepitus itself does not affect knee function or strength. Crunching also occurs in people without knee pain.

Crepitus and osteoarthritis

The connection between crepitus and osteoartitis in 2021. studied by Pazzinatto et al. It was then found that participants with osteoarthritis (OA) and crepitus had lower subjective knee functional ratings than participants without OA and crepitus. However, when objectively comparing knee function and condition, no difference was found between the two groups. The study authors concluded that knee crepitus in patients with OA does not affect knee function, function, or pain.

However, due to the patient's beliefs and concerns about noise in the knee, crepitus may well become a problem and have a negative effect on the patient's perception of their health.

Crepitation in the lungs

Most often, crepitus is heard in the lungs.

It appears in the alveoli at the last moment of maximum inspiration. This origin is caused by the accumulation of fluid in the alveoli, causing the pulmonary vesicles to “stick together” .

With a strong inhalation, at the moment of maximum expansion of the lung tissue, the alveoli come apart, which is why a characteristic sound is created. Thus, crackling is heard only at the peak of a deep breath, at the moment of high pressure in the bronchi and straightening of the alveoli. In this case, the auscultated crepitus often has an explosive sound, which consists of a mass of quiet clicking sounds. The force depends on the number of adherent alveoli, which are straightened at the moment of inhalation.

What are the beliefs about a crunch in the knee and how do they affect human behavior?

In 2021 Roberston et al. conducted a qualitative study examining different beliefs about knee crepitus and how these beliefs influenced people's behavior. Here are the three main ideas from this study:

Beliefs about noise

Study participants said it was extremely important for them to know what knee sounds mean and why they happen. Most of the respondents tried to find the reason on the Internet, they also asked medical workers about this, but did not receive clear answers. Some were convinced that a crunching sound in the knee indicated the aging process, and also that this sound was the result of bones rubbing against each other. In general, participants associated the origin of sounds with something negative, which was associated with a lack of understanding of where they actually come from.

Influence of other people - friends, relatives and doctors

Many participants also paid attention to how their friends and relatives reacted to the crunch. And many admitted that their reactions - body language, facial expressions (loved ones winced, winced and grimaced) - only added fuel to the fire, making them worry even more.

Study participants also expressed dissatisfaction with representatives of the medical profession, who often ignored their problem, and sometimes did not even understand where these sounds were coming from. Among those surveyed were those who had discussed the problem with their doctor, and in this group the view of crepitus was much more positive.

Avoiding noise

Due to the fact that many participants were convinced that crunching in the knees was dangerous and would lead to the destruction of the joint, some ended up completely abandoning certain movements in which the sound excites them. They also began to avoid certain activities that they thought might cause crepitus.

conclusions

The study shows that education by health care providers regarding crepitus in the knee is of great importance. Patients need to understand where these sounds come from and why.

For patients whose crepitus is associated with a pathology (for example, when a specific click occurs indicating a meniscal tear), the best therapy is to treat the underlying cause. Treating the underlying cause may also resolve the crepitus problem.

In most patients, crepitus in the knees is physiological and is not associated with any pathology as such. Such patients need to be explained how the crepitus occurs, and also convey the information that crepitus is not dangerous, does not harm the knee and does not cause osteoarthritis.

Subcutaneous crepitus

Crackling under the skin occurs when gas is pumped into the subcutaneous tissue - subcutaneous emphysema. This phenomenon is observed quite rarely, since this requires a special lesion of the lungs, in which the integrity of the airways is damaged. Due to which gas bubbles enter the blood or surrounding tissues.

The causes of subcutaneous emphysema may be the following:

• pneumothorax with rupture of the outer pleural layer;
• fractured ribs with a lung injury from a bone fragment;
• penetrating lung injury;
• rupture of the airway in the middle or lower section;
• esophageal rupture;
• anaerobic infections.

Violation of the integrity of the respiratory tract leads to air bubbles penetrating into the surrounding tissues or blood. The penetration of gas is facilitated by the fact that the pressure in the pulmonary tract is constantly changing due to the respiratory process. Most often, air penetrates into surrounding tissues, but can be carried throughout the body through the blood. In this case, swelling of the subcutaneous tissue with crepitus can be detected in various parts of the body.

More often, emphysema has small borders around the site of injury or damage to the lung. But with extensive damage, symptoms spread to the entire chest, back, neck, head, abdomen, shoulders, armpits and thighs. Although it does not cause harm, the widespread distribution of gas bubbles is dangerous because they can cause heart attacks of internal organs. In addition, a high prevalence indicates serious damage to the lungs.

The causes of subcutaneous emphysema may be the following:

• pneumothorax with rupture of the outer pleural layer;
• fractured ribs with a lung injury from a bone fragment;
• penetrating lung injury;
• rupture of the airway in the middle or lower section;
• esophageal rupture;
• anaerobic infections.

Violation of the integrity of the respiratory tract leads to air bubbles penetrating into the surrounding tissues or blood. The penetration of gas is facilitated by the fact that the pressure in the pulmonary tract is constantly changing due to the respiratory process. Most often, air penetrates into surrounding tissues, but can be carried throughout the body through the blood. In this case, swelling of the subcutaneous tissue with crepitus can be detected in various parts of the body.

More often, emphysema has small borders around the site of injury or damage to the lung. But with extensive damage, symptoms spread to the entire chest, back, neck, head, abdomen, shoulders, armpits and thighs. Although it does not cause harm, the widespread distribution of gas bubbles is dangerous because they can cause heart attacks of internal organs. In addition, a high prevalence indicates serious damage to the lungs.