Osteoarthritis of the knee joint is a chronic degenerative-dystrophic disease characterized by progressive degradation and loss of tissues of the articular cartilage of the knee. Due to the pathology that destroys the joint, pain in the leg, and limitation of mobility develop. In medical terminology, this pathogenesis is often called gonarthrosis – a concretizing term that directly indicates the knee localization of osteoarthritis (arthrosis). According to the latest data from  researchers, in USA for every 10 thousand population, 100-120 people are sick with gonarthrosis. Experts predict a doubling of the number of cases by 2020.

Arrows indicate the area of ​​degradation of the internal condyle of the right CS.

Osteoarthritis of the knee joint is an insidious pathological process, according to statistics, it causes a noticeable decrease in the quality of life in 80% of patients, and in 10% -21% it causes disability. People of the elderly age group are especially susceptible to rapid disability. Osteoarthritis most often affects the knee section, that is, in terms of frequency of occurrence among all degenerative-dystrophic articular pathologies, gonarthrosis takes 1st place. In the structure of all orthopedic diseases, this pathology accounts for 30% to 55%. The disease can affect both one joint and two knee joints at the same time. Observations have shown that about 30% of patients with a confirmed diagnosis have bilateral OA (both knees are affected).

The prevalence of knee OA is slightly higher in women than in men. At the same time, at the initial treatment in the group of male patients, young people predominate – up to 45 years, in the female group, patients from 55 years and older predominate. At the age of 65+, regardless of gender, radiological signs of pathology in varying degrees of severity are diagnosed in 80% of people. The basis of the etiology of pathogenesis is formed by numerous acquired and congenital factors, where one of the leading places is occupied by chronic trauma to the articular ends of the knee apparatus due to an improper exercise regimen. This is not the only reason, all provoking factors will be indicated during the article.

Osteoarthritis of the knee joint leads to a permanent loss of function of an important biological segment of the limb. A person begins to experience difficulties in walking, torment from pain, often the patient becomes dependent on special supporting devices and outside help. In fact, the disease dramatically reduces the ability to work and social adaptation of the individual, in addition, it has a negative impact on the psychological state. It is also alarming that about 2/3 of patients are people of working age, who are only 40 to 60 years old. Based on this, the treatment should be well planned and carried out immediately. 

The sooner the pathological process is identified, the more hopes can be pinned on the effect of conservative care. But it’s not that simple. It was noticed that about 40% of patients visit doctors too late, when degenerations have already thoroughly destroyed the knee joint and complications followed. Unfortunately, conservative methods do not work for advanced forms and late stages of the disease, only surgical intervention can help here.

Causes of osteoarthritis of the knee joint

The underlying reason for the mechanism of the appearance of pathology is a violation of the metabolism of cartilaginous structures with a shift in the balance of catabolism-anabolism, that is, when the processes of destruction of cartilage cells prevail over recovery. Initially, irreversible changes undergo hyaline cartilage covering the articular surfaces of the joint, and the subchondral plate, which is located under the articular cartilage. OA is characterized by a progressive course, and it does not stop at the destruction of the hyaline coating and subchondral bone. As the progression progresses, degenerative pathogenesis is able to become more or less active in all constituent units of the knee – menisci, synovial membrane, capsule, ligaments, etc.

The pathoetiology of osteoarthritis of the knee joints is quite diverse. Experts have identified the main common factors-provocateurs of the disease, we will consider them.

1) Inadequately high level of physical activity and stress on the lower trunk in everyday life:

  • doing professional sports, dancing; 
  • Excessive walking during a work shift 
  • frequent weight lifting; 
  • long squatting or with the knees tucked under oneself, standing / moving on the knees;
  • significant load at the household level (disproportionate work at home, in the country, etc.).

2) Previous knee injury:

  • local bruises, for example, falling to the knee, hitting it with something;
  • local dislocations and muscle strains;
  • damage to the ligamentous apparatus (tears, sprains);
  • meniscus injuries with displacements, tears, half-tears;
  • fracture of the kneecap or condyles, fibula, femur, or tibia.

3) Congenital anomalies in the structure of the musculoskeletal and muscular apparatus ( dysplasia ):

  • underdevelopment/deformation of the lower leg;
  • weakness/shortening of the thigh muscles;
  • congenital dislocation of the patella;
  • joint hypermobility;
  • congenital valgus or varus position of the knees.

4) History of comorbidities, for example:

  • gout;
  • rheumatism;
  • diabetes;
  • lupus erythematosus;
  • thyroiditis;
  • severe allergic diseases;
  • local varicose veins, etc.

5) Overweight: 

  • with a BMI of 25.1-27 kg / m2 (medium risk);
  • with a BMI of 27.1-30 (high degree);
  • with a BMI of more than 30 kg / m2 (critically high predisposition to gonarthrosis).

6) Previously performed non-osteoarthritis-related knee surgery, for example:

  • meniscectomy ;
  • plastic ligaments ;
  • installation of clamps, plates for fractures, etc.

7) Low physical activity:

  • with a deficit of motor activity in the limbs, blood supply decreases, metabolic processes are inhibited, muscles and ligaments lose strength, which creates a fertile ground for the appearance of degenerations in the knee and other joints of the legs.

8) Postmenopause.

  • with the onset of menopause in women, the production of estrogens is significantly reduced, and these hormones in a reduced amount are not able to exert a protective effect on the joints at the same appropriate level as before.

As one of the reasons, experts call heredity. If your parents or grandparents suffered from osteoarthritis, then you are at risk. In addition, people aged 45 and older are more vulnerable to the disease. From the age of 45, there is a marked reduction in biological functions, the body undergoes the so-called age-related metabolic stress, due to which the bone and cartilage tissues lose their former strength. 

Any factor from this list (or a combination of 2 or more) can serve as the beginning of a local metabolic disorder in the knee joints and, as a consequence, the development of osteoarthritis. On the rubbing articular surfaces, enveloped in hyaline cartilage, cracks, fibrillation, and ulceration appear. The cartilage becomes thin, inelastic, rough, and bumpy. In this regard, the shock-absorbing and sliding properties of the joint are reduced, the movements between the articulating surfaces are hampered due to the death of the cartilage tissue and the decrease in the joint space for the same reason.

What the surgeon sees during the operation. The hyaline cartilage has surface damage.

Pathologically increased intra-articular friction, along with progressive biochanges, ultimately leads to the fact that the cartilaginous zone completely disappears (erased), the subchondral plate is partially or completely destroyed, the abutting bone ends are exposed. The exposed condyles of the femur rub against the exposed tibia in the upper epiphysis and / or against the patella, a pathological displacement of the contact surfaces occurs, the joint is more and more deformed. 

Due to the fact that the disease leads to deformities of the articular structure, in medical terminology one can often find such a formulation of the diagnosis as “deforming osteoarthritis of the knee joint”. Severe deformities are most characteristic of the later stages of development. Therefore, the word “deforming” is often used by doctors in relation to the last stages of osteoarthritis. 

Symptoms: early, late onset

The main complaint of knee OA is pain. At the onset of the disease, the pain, as a rule, is of a mechanical nature, that is, it manifests itself and increases at the moment or after prolonged physical activity, with a long standing in one place or going down stairs, at the end of the working day. Painful signs can be felt both from the inside and on the front, back, side of the knee. By the nature of the first pain, as a rule, aching, dull, pulling. At first, it is fickle and mild, and at first it is caused by muscle spasm. Early mechanical pain caused by physical exertion has its own peculiarity: during periods of rest and rest, it subsides on its own (this is uncharacteristic for later stages). One of the first symptoms is also morning stiffness in the problem knee, which usually lasts 30-40 minutes until the person leaves. 

Pain in the knee joint when walking up stairs.

Long-lasting and often manifested pain sometimes (more often in the initial, intermediate stages) provokes secondary synovitis, which is why it is felt at rest. Excessive accumulation of synovial fluid, as a reaction to pain and inflammation, in addition causes problems with flexion/extension of the knee or aggravates the existing flexion-extensor dysfunction. In the expanded stage, starting pain options are possible, which means the appearance of pain syndrome with the onset of walking, which decreases during movement in 15-30 minutes. Painful phenomena may reappear with a continued increase in the load on the problem knee. 

Neglected cases are often accompanied by the occurrence of joint wedge syndrome. Jamming is characterized by sudden, sharp pain of a shooting nature and blockage of movements in the knee region. Painful shock together with the blockade is provoked by the presence of free chondromic fragments (pieces of cartilage) in the intra-articular space, which are pinched between the articular surfaces. A mechanical obstacle in the form of wedging can also create a bone thorn (osteophyte) that penetrates into soft tissues. The blockade is eliminated with a kind of turn of the leg, but not always a person independently copes with unblocking the knee. 

We have characterized the common variants of pain syndrome development, but it is worth noting that along with it there is a significant decrease in the range of motion, stability functions, and a modification of the forms of the musculoskeletal segment. There is pain at an early stage, but in general, the functions and configuration of the joint are still almost fully preserved. With the onset of the second and subsequent phases of the disease, their progressive violation is noted, and other symptoms appear. For complete clarity of the clinical picture, we present all the symptoms typical of knee osteoarthritis:

  • local pain syndrome, especially in movement;
  • a feeling of tightness, stiffness in the knee;
  • articular crepitus during movement in the form of grinding, crunching, clicks;
  • painful and / or difficult flexion, extension of the leg, rotation;
  • weakness of the quadriceps femoris muscle (the femoral muscles undergo severe atrophy with advanced gonarthrosis);
  • a feeling of bowing of the sore leg;
  • swelling and warming of the skin over the joint;
  • change in gait stereotype (lameness progresses in the penultimate, last stages);
  • valgus or varus curvature of the sick lower limb (develops in the later stages). 

The longer the period of the disease, the brighter, more often, the longer the knee joint hurts. Moreover, he can disturb not only during exercise, but also in an immobilized state, including during a night’s sleep. Moreover, an increase in degenerative changes will steadily narrow the range of active and passive movements, bringing it to a minimum as a result.

Good to know! In primary OA of the knee, the risks of forming a similar type of lesion on the same limb, but in the hip region, are 15% -18%. And the likelihood of developing coxarthrosis on the opposite side of the problem knee is within 30%. The knee and hip joints are very closely interconnected functionally – a problem in the knee, as a result, can badly affect the hip joint and vice versa. Therefore, do not self-medicate, this disease requires a professional approach, individual for each individual case.

Diagnostics: examination methods

For osteoarthritis of the knee joint, as well as for other joints, there are no pathognomic laboratory signs. In most patients, blood and urine tests show normal results. Therefore, laboratory research methods are not of clinical value. The generally accepted method for detecting gonarthrosis is currently radiography of the knee joints. X-rays are necessarily initially done on two joints for the purpose of anatomical and physiological comparison of two bone joints of the same type. There are 3 main radiographic signs, according to which one can assert the presence of this diagnosis, are:

  • osteophytes along the periphery of the articular surfaces;
  • narrowing of the joint space (normally its width is 6-8 mm, the parameters depend on many factors, including height, age, gender, etc.);
  • subchondral osteosclerosis.

Bilateral absence of joint spaces.

However, these signs in the very, very initial period of the development of osteoarthritis on the X-ray may still be absent. If the doctor does not see any abnormalities on the X-ray data, and the patient comes with complaints of periodic pain or, for example, recurrent swelling for unknown reasons, it is important to conduct an additional examination. It is also advisable to include an additional examination in the diagnostic process and, if the diagnosis is established, radiographically in order to obtain detailed information about the condition of the knee structures, in particular soft tissues and intra-articular fluid. 

Magnetic resonance imaging (MRI) and arthroscopy are recognized as the best auxiliary methods for OA at any stage, as well as for differentiating this pathology from others . As for computed tomography: it is inferior to the capabilities of these two procedures, since it does not clearly visualize soft tissues. Ultrasonography (ultrasound) of all methods is the weakest diagnostic tool.


MRI shows even the smallest superficial cartilage lesions at the articular ends, and it is from this cartilaginous structure that the first dystrophic changes begin to occur. In addition, according to MRI data, an objective assessment of the state of the synovial membrane, capsule, surrounding muscles, tendons, ligaments, neurovascular formations, and produced synovia can be given. Magnetic resonance imaging machines detect cysts and other neoplasms, including bone defects. 

Arthroscopic diagnostics has not the worst capabilities, but it involves minimally invasive intervention with the introduction of an imaging optical system into the knee joint. With the help of arthroscopy, in addition to high-quality examination from the inside of all structural elements of the joint, in parallel, it is possible to puncture the intra-articular effusion, to clear the cavity from the so-called arthritic “debris”.

View through the arthroscope.

In addition to instrumental methods, the structure of the diagnosis necessarily includes the conduct of special tests during the initial examination. The doctor performs palpation of the lesion site, assessment of the range of motion in various positions of the examined area of ​​the limb, determination of sensitivity disorders. After a diagnosis of a similar plan is established, a test examination and radiography will be periodically performed to monitor the condition of the knee region and assess the effectiveness of the therapy.

Stages and degrees of osteoarthritis of the knee

Classification of the stages of knee OA in orthopedics is offered in two versions: according to N.S. Kosinskaya (3 stages) and according to Kellgren-Lawrence (4 stages). In domestic practice, both the first and the second classifier of lesions of the osteoarticular apparatus are equally often referred to. Both classifications are focused on determining the following features: 

  • decrease in height and unevenness of the inter-articular gap; 
  • deformation of articulating surfaces; 
  • the presence of defects with pronounced contours; 
  • thickening of the subchondral areas of the bone due to osteosclerosis; 
  • the formation of subchondral cysts (on the x-ray they look like light spots in the area of ​​the femoral and tibial condyles, within the patella). 

From left to right the dynamics of destruction is shown.

We suggest that you familiarize yourself with the staging of gonarthrosis

Stage X-ray signs, clinical manifestations
I (light) The changes are subtle and can be perceived as normal. The slit in the direct projection can be normal or slightly narrowed. It is possible to detect a slight narrowing of it when comparing the right and left joints. It will unambiguously tell about the incipient functional and morphological malfunction of the cartilage, light osteophytosis. It is a compensatory reaction in response to changes in the elastic properties of the cartilage. Osteophytosis at this stage is poorly expressed, characterized by the presence of tiny osteophytes in a single amount along the edge of the articular bones. However, at the initial stage, there may not be any marginal growths at all.

Clinically, stage 1 is relatively mild with low-intensity short-term pain due to prolonged physical fatigue and minimal impairment of knee functions, which many people do not perceive as something serious.

II (moderate) The size of the joint space of the knee, in comparison with the norm, is sharply reduced by 2-3 times. Such a strong contraction of the gap indicates the already burdened morphology of the articular cartilage, the severity of its damage. Mainly, the narrowing of the gap is characterized by unevenness, in accordance with the severity of the degenerative process. The epicenters of maximum narrowing are concentrated in the articular zone, which accounts for the highest proportion of the load. The medial (inner) part of the joint often becomes such a zone. 

At stage 2, large osteophytes are also found along the edges of the articular surfaces, sclerosis of the endplate is detected, sometimes cystic rearrangement of the subchondral bone is determined. X-ray images show a slight violation of congruence, moderate deformation of the bony epiphyses that form the knee joint.   

It is manifested by a pronounced aggravation of the functions of the knee apparatus with an obvious restriction of movements, which in the initial phase were sometimes a little difficult. Additionally, a relatively moderate limitation of all other types of physiological movements, crunching, limping is added. The pain is severe, often there is a slight local swelling, there is muscle wasting near the joint. 

III (severe) The slit gap between the surfaces of the joint completely disappears or is traced, but with very great difficulty. At the final stage, many sharp and massive osteophytes are found, which totally surround the articulating surfaces, merging with the adjacent bone. The X-ray picture shows the gross deformities of the knee articulation (impressive expansion and flattening of the surfaces), significant osteosclerosis of the epiphyses of the knee bones, the presence of CX cysts. The joint is expressively deviated from the vertical axis of the limb (along the valgus or varus). 

The clinical picture of manifestations is characterized by a visible thickening of the knee and its forced position. The locomotor and support potential of the joint is reduced to a critical level, while crepitus is no longer manifested in it. The muscles are atrophied throughout the leg, the quadriceps muscle is particularly affected. The limb is completely incapacitated, it is impossible to move independently, lameness progresses. Pain syndrome reaches its peak, becomes extremely painful, disturbing constantly, regardless of the time of day and physical activity. The third stage disables the person.

Conservative and surgical treatment

The principle of treatment – conservative or surgical – is selected on a strictly individual basis by a highly qualified specialist of the appropriate specialization. The attending physician is an orthopedist or orthopedic traumatologist. Immediately, we note that this pathology is by its nature incurable. Unfortunately, there is no turning back to the onset of degenerations and their consequences. The revival of cartilage, the natural restoration of the forms of the joint due to the biological characteristics of the osteo-cartilaginous system cannot be achieved, no matter what pills, injections, physiotherapeutic, manual techniques are used for the therapeutic effect.

Therefore, it is important to clearly understand that conservative methods are designed for preventive and symptomatic purposes, namely:

  • prevention of osteoarthritis (if not already); 
  • suppression of the rate of degeneration (with the onset of the disease) due to the activation of trophism of tissues in the knee joint, changes in lifestyle, competent distribution of loads on the musculoskeletal system; 
  • relief of pain and inflammation, reduction / prevention of atrophy and contractures; 
  • improving limb mobility and quality of life, as much as possible with the existing pathogenesis.  

It has been proven that productive results can be expected from conservative treatment when it is introduced at the initial stage of the disease and partly at the start of stage 2, while most of the cartilage is still preserved. Closer to the middle of the 2nd stage of development and at the 3rd stage, medical and physical measures lose their strength, for the most part they do not even help to move in the slightest degree in the positive direction.

Non-surgical tactics to control the disease include the complex use of physical and drug rehabilitation methods (courses):

  • local and external NSAIDs (eg, Ibuprofen, Diclofenac or Ketoprofen, Meloxicam) for pain;
  • chondroprotectors that can slow down the progression of gonarthrosis (Don, Aflutop, Structum, etc.);
  • (vitamins E, C and B, potassium orotate, FiBS, etc.);
  • physiotherapy exercises (developed, appointed by a doctor, training should be carried out exclusively under the guidance of an exercise therapy trainer);
  • physiotherapy (electrophoresis, pulse therapy, ultrasound, magnetic therapy, baths based on hydrogen sulfide and radon, etc.); 
  • intra-articular injections of corticosteroids, used in extreme cases, for   unbearable prolonged pain with frequent relapses, severe synovitis that cannot be stopped by conventional non-steroidal drugs.

If the first course of steroid injections into the joint is not effective enough, it no longer makes sense to carry out it, an urgent need to operate on the knee.

It is undesirable to delay the operation in the absence of the effect of conservative therapy. Timely surgery will make it possible to carry out surgery without difficulties, it is easier to transfer the surgical procedure with minimal risks of complications, and to recover faster and better. The priority system of treatment in modern orthopedics and traumatology for advanced forms of OA with localization in the knee joint remains surgical intervention using the method of endoprosthetic . Endoprosthetics – replacement of the knee joint with a functional endoprosthesis – allows in a short time: 

  • completely correct knee deformities (O-shaped, X-shaped); 
  • qualitatively restore the anatomy and functions of locomotion, support stability, shock absorption in the problem segment of the limb; 
  • return the patient to painless physical activity, eliminating disability, and restoring the normal level of working capacity. 

Depending on the indications, the individual characteristics of the patient’s body, prosthetics can be performed on the principle of partial or total replacement of the joint with cement, cementless or hybrid fixation. The unique prostheses completely imitate the mechanics and anatomy of the “native” human joint or its individual components. They have the highest strength, the best qualities of rigidity and elasticity, excellent biocompatibility with the body, surrounding biological tissues, fluids. Implants are made from high-tech metal alloys (titanium, cobalt-chromium, etc.). Full structures last 15 years or more on average , but subject to a perfectly performed operation and postoperative rehabilitation.

Before the implantation of the implant, the affected bone connection is removed, the surfaces of the articular bones undergo thorough surgical treatment and preparation for the installation of the endoprosthesis. If a patient will receive a total endoprosthesis design, it will consist of a fully assembled artificial copy of a healthy knee joint, including: 

  • a fixed or mobile tibial component in the form of a platform on a pedicle, identical to the shape of the surface of the corresponding bone;
  • a polyethylene liner (shock-absorbing “pad”), which is fixed in the tibial component;
  • the femoral component is rounded, corresponding to the shape of the femoral condyles;
  • an element of the patella (it is not always installed, only if the cartilage layer of the patella is in poor condition).

Partial replacement (single-sided) implies minimally invasive prosthetics of only one half of the knee joint – the medial or lateral femoral-tibial bone junction. After any type of endoprosthetics, a comprehensive rehabilitation is carried out, aimed at preventing postoperative consequences, restoring the muscles and movements of the prosthetic limb. Rehabilitation after replacing the knee joint continues until the patient is fully recovered, usually 2.5-4 months.


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