Why do my knees crunch when bending and extending?

If a crunch is heard in the knee joint while walking or bending the leg, several questions arise at once: why do knees crunch, what does this sound mean, is it dangerous and what to do? Answers to all these questions are given by orthopedists, calling the crunch in the knees intra-articular crepitation. It can be felt much more often if you put your hand on the kneecap while bending the leg in the knee joint and straightening it.

Causes of the knee crunch

Quite a few people feel crackling in knee joints while walking or hear their knees crunching when climbing stairs, bending and extending them - when squatting. Young people complain of knee crunching after running, older people complain of heaviness and crunching in the knees, and some people have had crunching knees since childhood.

So, the crunching sound - if the knees crunch without pain and reduction in the degree of mobility of the lower limbs - is considered physiological. Its etiology, i.e. Causes, is explained by experts based on anatomy of the knee joint and its biomechanics, but in slightly different ways.

Some people claim that the crunch is caused by cartilage rubbing on the joint surface. Others believe that crunching and clicking occurs when the knee is bent and the articular surfaces of the articulating bones (femur, tibia and patella, i.e. Kneecap) move slightly away from each other as the volume of the intra-articular capsule increases and the pressure in it decreases. In this case, cavitation bubbles are formed in the synovial fluid (cavitas in Latin means "void"), which quickly fill with gas (carbon dioxide) dissolved in the fluid and then burst with a characteristic sound.

The third opinion is that the sound accompanies not the bursting of bubbles, but their formation itself. And, according to recent studies, the crunch in the knees is the result of the appearance of a gas cavity in the viscous synovial fluid, associated with a drop in its pressure during joint movement. In addition, synovial fluid (consisting of a mixture of filtered plasma proteins and glycosaminoglycans) exhibits the properties of dilatant non-Newtonian fluids: it becomes more viscous at the moment of strong or sharp shear of joint surfaces, less viscous with increasing joint speed, and simply moves away from the point of greatest force application during static loading.

It is also not unreasonably assumed, often crunch knees and elbows, as well as other diarthroses (freely moving joints) - without the slightest painful sensation - due to weakness of the capsule-ligamentous apparatus that holds the bone surfaces entering the joint and provides stability of the knee diarthrosis as a whole.

And here it is impossible not to mention the fact that a large number of women have crunchy knees for some time after childbirth. The reasons lie in the fact that during pregnancy, changes occur in the musculoskeletal system under the influence of the hormone relaxin. After the birth of the child, this hormone circulates in the blood of women for some time, having a relaxing effect on the ligaments of the joints - which causes a certain instability of the joints, for example, a freer movement of the patella.

Another important factor: the increase in body weight in pregnant women, which, of course, increases the load on the knee joints, because each gained kilogram puts four times more pressure on them.

Knee cracking is noted after surgical interventions on them, and most often there is crunching in the joint after knee endoprosthesis: this is how the endoprosthesis is "lapped", and this may be accompanied by its vibration and reduced stability of the knee. According to the data of foreign clinics, after installation of a prosthesis in the posterior part of the knee diarthrosis, crunching of the knee cap occurs in more than 15% of operated patients.

Why crunch knees in a child: norm and pathology?

When the knee crunches when bending in the infant, doctors explain it to worried parents not fully formed joint and ligament system of the child, as well as insufficient production of synovial fluid, because of which when the joint surfaces touch, they rub and crunch.

In the first 24 months of life, children have higher joint mobility, as their skeletal structures (compared to adults) contain much more cartilage, which corresponds to physiological norms: for example, the kneecap of infants consists of cartilage tissue and turns into bone only by the age of 8-10 years. This is why a child often has crunchy knees and other diarthroses, which in the majority of children goes away with age.

In some cases, even in newborns, the knee crunches and clicks when it is extended. This is possible when the meniscus of the knee joint from birth has a shortened posterior ligament connecting it to the medial condyle of the femur. This anatomical feature causes a posterior displacement of the cartilaginous disk during knee extension, accompanied by a rather loud clicking sound.

Many children of the same age have such a widespread variant of skeletal-muscular anatomy as genu varum - physiological bending of the lower limbs with angular deformation of the knee, which is called varus knee and is also manifested by the fact that the infant's knee crunches. Normally, by the age of two, this condition gradually subsides: the knee joints come closer together, the hips and shins straighten, and the feet are placed straight in a sitting position.

But it should be borne in mind that such curvature of the lower limbs may be one of symptoms of rickets (including vitamin D-resistant rickets) or a sign of an osteogenesis abnormality. [1] And when a varus knee remains unchanged in a child over the age of two, it is a bad sign and should be examined - to rule out Blount's disease, [2] Koenig's disease, [3] multiple syndromes and genetic joint or skeletal abnormalities.

More about abnormalities. In both older children and adolescents, the knees can not only crunch, but also hurt quite badly, as detailed in the publications:

• Knee pain in children
• Joint pain in children

Why do adult knees hurt and crunch?

While knee crunching by itself may not cause much concern, the presence of other symptoms - when your knees hurt and crunch, or your knee is swollen and crunchy and has difficulty moving - indicates a serious joint problem that requires medical attention.

When the knee often hurts and crunches after running, especially long-distance running, as well as after other intense knee diarthrosis movements, specialists may diagnose patellofemoral (patellofemoral) pain syndrome. It is caused by overloading the patella (due to increased pressure between the kneecap and the thigh) and can provoke chondromalacia of the patella with softening of the articular cartilage and a decrease in its thickness. In this case, crunching and clicking in the knee when walking, intense pain in the knee joint, you may also feel pain after crunching in the knee. [4]

Painful and crunchy knees when squatting and climbing stairs are also due to damage to the cartilage of the kneecap with its displacement due to constant increased loads on the knee joints (including excessive body weight), abnormal location of the bony structures of the knee joint, knee trauma. [5]

Almost always the knee hurts and crunches after an injury - a bruise or a fall: a direct blow to the kneecap can damage the articular cartilage, and then the knee crunches after a bruise.

Knee crunching after a fall is due to mechanical damage to the cartilage surface, as well as to damage to the menisci of the knee joint. If the crunch is associated with pain in the knee, the joint is swollen and its flexion-extension is accompanied by clicking, these are symptoms of a meniscus tear. [6], [7]

In stretching of knee joint ligaments there is crunching of ligaments in the knee. Its mechanism is explained by the fact that the corresponding ligaments, stretching, touch the condyles and intermuscular elevation of the joint, and the patella is displaced. For example, crunching under the knee, or more precisely, under the kneecap, if the anterior cruciate ligament inside the joint is damaged. [8] There is instability of the joint structures, as well as pain and crunching in the knee in cases of patella ligament tears. [9]

When, against the background of pain syndrome, the knee is swollen and crunches when climbing stairs or sitting cross-legged for a long time, knee arthrosis (which can progress to a deforming form of the disease) should be suspected.

The pathogenesis of osteoarthritis of the knee joint (gonarthrosis), accompanied by pain in the knee when squatting and crunching when walking, is associated with degenerative changes and destruction of cartilage, which loses its protective properties, and between the surfaces of articulated bones begins friction, leading to their deformation. At the beginning of the disease at times aching and crunching of the knee when moving, but as the disease develops, the pain increases and bothers even at rest. [10], [11]

Risk factors

Is it possible to list all the risk factors for knee crunch and arthralgia - taking into account the individual anatomical features of the knee joint, its ligamentous apparatus and adjacent muscles, as well as the level of load on the knee diarthroses in each person? But certainly these factors include:

• All forms of arthritis (including rheumatoid and tuberculosis);
• most degenerative joint diseases, primarily osteoarthritis and osteoarthritis;
• age-related degenerative-dystrophic changes in bone and connective tissues;
• joint hypermobility;
• joint pathologies of metabolic origin, for example pyrophosphate arthropathy, calcinosis or chondrocalcinosis;
• Weakening of skeletal bones and osteochondropathies of any etiology;
• ossification of ligaments and tendons;
• Hyperparathyroidism (with impaired calcium and phosphorus metabolism in the body);
• connective tissue dysplasia, leading to joint hypermobility;
• deformity of the lower extremities;
• collagenoses, including autoimmune diseases (lupus, scleroderma);
• inflammatory processes affecting tendons (tendonitis) or the synovial membrane of the knee joint (synovitis);
• Disorder of protein metabolism - amyloidosis (with protein deposits in the inner lining of the joint cavity);
• insufficient production of intra-articular fluid - the main joint lubricant - and changes in its viscosity;
• overweight;
• lack of motor activity and, on the other hand, prolonged physical overload, including sports.

Just in case, check it out - Occupational Diseases of Athletes

Diagnostics of the knee crunch

What doctor should I see if my knee hurts and crunches? In such cases you should go to orthopedist, and if your knee hurts and crunches after an injury - to orthopedist-traumatologist. Also can help arthrologist.

These are the specialists who perform joint diagnostics, which include:

• anamnesis, examination and determination of the functional status of the knee joint (based on physical tests);
• tests, including a general blood test, for COE, C-reactive protein, rheumatoid factor, calcium and uric acid levels in the blood; a general clinical analysis of synovial fluid is done (by arthrocentesis).

Instrumental diagnostics - diagnostic knee arthroscopy, knee x-ray, MRI or knee ultrasound - visualizes all joint structures.

Based on all the data obtained, a differential diagnosis can be made, but not crunching in the knees, but diseases or pathologies of knee diarthroses.

Treatment of the knee crunch

Specialists say that when crunching knees without pain and other symptoms, there is simply nothing to treat, as there are no drugs for crunching knees, as such, and it cannot disappear.

But if there are other symptoms, the treatment, usually long term, will depend on the diagnosis.

In orthopedics for conservative therapy of joint diseases are used:

• Gentle regimen (maximal reduction of physical activity, e.g. In case of exacerbation of patellofemoral pain syndrome);
• splinting of the joint (to provide rest, especially in case of injury);
• Nonsteroidal anti-inflammatory drugs (Diclofenac, etc.) and other knee pain pills.

Read also:

• Arthritis pills
• Osteoarthritis pills
• Osteoarthritis of the knee joint: treatment
• Treatment of osteoarthritis

Widely used external means - various ointments and creams:

• Ointments for knee pain
• Ointment for joint pain
• Ointments for osteoarthritis

For diseases of joints and tendon and ligament structures are prescribed:

• vitamins (C, D, B group);
• oral agents for cartilage repair - chondroprotectors containing chondroitin sulfate (Structum, etc.);
• intra-articular injections hyaluronic acid for joints;
• Plasmolifting (injections of autoplasm to restore an optimal amount of synovial fluid).

Physiotherapy treatment is used, for details see. - Physiotherapy for joint diseases

Outside the exacerbation of arthralgia extremely useful for any mobile joints therapeutic exercise, and exercises from crunching in the knees consist of walking in a regular rhythm, alternate bending of the legs at the knee (at right angles of the thigh), lunges forward with one and the other leg, etc.

In this regard, some people are interested in how to treat crunch in the knees according to Bubnovsky. So, Dr. S. Bubnovsky treats joints with the help of movement, and his system is called kinesitherapy. Read more about his methodology in the article - Arthritis? Osteoarthritis? Positive prognosis!

In extreme cases, when the condition of the knee joint threatens complete loss of the ability to move independently, surgical treatment is required: arthroscopy, as well as joint endoprosthesis.

Complications and consequences

Considered separately, persistent crunching of the knees is considered by many orthopedists to be a prognostic factor in the development of osteoarthritis and osteoarthritis, as friction of the joint surfaces can have consequences: wear and tear of cartilage and weakening of bone.

However, this statement remains controversial, as knee crunch without pain is categorized as a non-pathologic condition, and in most cases does not arise from friction of the articular surfaces...

Although middle-aged and especially elderly people whose knees crunch more often when they walk are obviously more likely to develop symptoms of joint disease - in the near or distant future. And those who hear their knees crunch on a daily basis have an 8-11% chance of doing so.

Prevention

The main prevention of knee problems, including wear and tear of the articular cartilage, is to strengthen the muscles in the front of the thigh and hamstrings, which reduces the load on the knee joint. Regular walking, swimming and cycling are all suitable for this.

In addition, exercise improves joint blood circulation and intra-articular fluid circulation, and maintains joint morphologic structure and function.

Also beneficial for healthy knees are omega-3 fatty acids and other products for cartilage, joint and ligament repair.