1

The study of biochemical indicators of the composition of the synovial fluid of the knee joint of people of different sexes and normal ages did not reveal statistically significant differences in the indicators of the protein spectrum and carbohydrate-containing compounds of the synovial fluid of the knee joints of a healthy person based on gender and age. In this study, the closest correlations with human age are indicators of γ-globulins and sialic acids.

synovial fluid

hyaluronic acid

total protein

sialic acids

1. Bazarny V.V. Synovial fluid (clinical and diagnostic value of laboratory analysis) / V.V. Market. – Ekaterinburg: Publishing House of the UGMA, 1999. – 62 p.

2. Biochemical studies of synovial fluid in patients with diseases and injuries of large joints: a manual for doctors / compiled by: V.V. Trotsenko, L.N. Furtseva, S.V. Kagramanov, I.A. Bogdanova, R.I. Alekseeva. – M.: TsNIITO, 1999. – 24 p.

3. Gerasimov A.M. Biochemical diagnostics in traumatology and orthopedics / A.M. Gerasimov L.N. Furtseva. – M.: Medicine, 1986. – 326 p.

4. Diagnostic value of determining hexokinase activity in the synovial fluid of the knee joints / Yu.B. Logvinenko [and others] // Lab. case. – 1982. – No. 4. – P. 212–214.

5. Lekomtseva O.I. On the question of the clinical significance of the study of glycoproteins in recurrent stenotic laryngotracheitis in children / O.I. Lekomtseva // Current problems of theoretical and applied biochemistry. – Izhevsk, 2001. – P. 63–64.

6. Menshchikov V.V. Laboratory methods of research in the clinic / ed. V.V. Menshchikov. – M., Medicine, 1987. – 361 p.

7. Pavlova V.N. Synovial environment of joints / V.N. Pavlova. – M.: Medicine, 1980. – P. 11.

8. Semenova L.K. Studies on age morphology over the past five years and prospects for their development / L.K. Semenova // Archives of anatomy, histology and embryology. – 1986. – No. 11. – P. 80–85.

9. Bitter T. A modified uronic acid carbazole reaction / T. Bitter, H.M. Muir/Anal. Biochem. – 1962. – No. 4. – P. 330–334.

In the literature, synovial fluid (SF) indicators are presented either with outdated data or with data without indicating the method used. In table 1 we present a number of reference values ​​and the results of our own studies of the SF of people who did not have registered articular pathology.

We did not evaluate the reliability of differences in the presented comparison groups using mathematical methods due to the use of different methodological bases in the literature.

It should be noted that our data do not contradict those presented in the literature. However, a number of indicators certainly require methodological clarification.

Materials and research methods

The study material consisted of 31 corpses of suddenly deceased people of both sexes (23 men and 8 women) aged from 22 to 78 years, who did not have articular pathology registered by an expert.

Statistical processing of the obtained results was carried out by the method of variation statistics, used for small samples, with a probability of p equal to 0.05. For each group of observations, the arithmetic mean, the mean square ratio, and the error of the mean were calculated. To study the correlation and construct a correlation matrix of heterogeneous characteristics, the software selects the following rules for calculating correlation coefficients: when calculating the correlation of two quantitative parameters - the Pearson coefficient; when calculating the correlation of ordinal/quantitative and ordinal parameters - Kendall's rank correlation coefficient; when calculating the correlation of two dichotomous characteristics - the Bravais contingency coefficient; when calculating the correlation of quantitative/ordinal and dichotomous characteristics - point-biserial correlation. In order for the program to identify the scale for measuring characteristics, at the stage of selecting the initial data, an interval of characteristics was introduced.

Research results and discussion

We estimate the concentration of total protein (TP) in synovium to be significantly lower than in the literature. The most commonly used methods for determining the concentration of OB are the biuret and Lowry methods, which differ in varying degrees of sensitivity and specificity. Lowry protein determination is more sensitive but less specific than the biuret method. In a number of sources, as well as in our work, the biuret method was used.

Of particular interest is the quantitative determination of the main specific component of SF - non-sulfated glycosaminoglycan - hyaluronic acid (HA) (a polymer of disaccharide sequences of acetylated amino sugar and uronic acid). It is known that it is included in the synovium in the form of a hyaluronate-protein complex and is embedded in the surface of the articular cartilage. In the cited sources, the determination of HA began with precipitation with specific precipitants, giving a quantitative assessment of its content by determining uronic acids. In our data, we present the amount of uronic acids after determination in native synovium, taking into account that glycosaminoglycan precipitants are not specific for their sulfated and non-sulfated forms. We judged the amount of sulfated glycosaminoglycans by the ratio of sulfates to uronic acids. The determination of sialic acids in native synovium characterizes their total content, i.e. the total concentration of free and protein-bound sialic acids in the composition of glycoproteins. Since plasma glycoprotein proteins trigger the cytokine cascade of the inflammatory response after desialylation, it is natural to expect a connection with the clinical characteristics of joint diseases with their determination in the synovium. We were unable to compare the data we obtained on the activity of proteolytic enzymes, since in reference sources the indicators of proteolytic activity are given with reference to the substrate protamine sulfate (and in our studies hemoglobin served as the substrate) or without reference to the substrate.

Due to the fact that age-related disorders of the metabolism of articular tissues largely determine the development of degenerative-dystrophic processes in the joints, and women suffer from osteoarthritis almost 2 times more often than men, and in accordance with the objectives set in our work, we assessed the age-related and gender-specific characteristics of the biochemical composition of the fluid. normal human knee joint.

We did not find significant differences in the biochemical composition of SG and women according to the indicators we determined, which is illustrated by the data given in Table. 2.

Table 1

The main chemical components of the synovial fluid of healthy people (in comparison of data from different authors and the results of our own research)

Indicators
Viscosity, mm, 2/s
Total protein, g/l (TB)
Protein, fractions, %, Albumin
α1-globulins
α2-globulins
β-globulins
γ-globulins
Hyaluronic acid, g/l				1,70-2,20
Sulfates, mmol/l,					1.08 ± 0.04
Sulfates/UK
Sialic acid, mmol/				0,16-0,42	0.36 ± 0.01

Notes * - the numbers in bold are those obtained from the authors’ own, after recalculating the dimensions,

** the composition of protein fractions in sources 2 and 4 is given according to K. Kleesiek (1978).

1 - V.N. Pavlova, 1980

2 - Gerasimov, Furtseva, 1986

3 - V.V. Bazarnov, 1999

4 - CITO, 1999

5 - own data

Table 2

Biochemical parameters of synovial fluid of the knee joints of men and women

Indicator	Men (n = 23)	Women (n = 8)
Total protein g/l (TB)
Protein, fractions, % Albumin
α1-globulins
α2-globulins
β-globulins
γ-globulins
Sulfates, mm/l
Sulfates/UK

Table 3

Values ​​of the correlation between biochemical parameters of synovial fluid of human knee joints and age

Note. Values ​​of the correlation coefficient that are significantly different from zero at the significance level p are highlighted in bold.< 0,05.

Table 4

Concentrations of γ-globulins and sialic acids in the synovial fluid of the knee joint of people of different age groups

Determining the correlation between age and the biochemical composition of the synovium, we calculated the coefficient and significance of the correlation for individual biochemical parameters, as well as the ratio of uronic acids to total protein and sulfates to uronic acids. We took the first ratio as an indicator of the accumulation of proteoglycan metabolic products, and the second as the degree of sulfation of glycosaminoglycans in synovia. The results of calculating correlation indicators are presented in table. 3. The indicators that change most with age are the γ-globulin fraction of protein and sialic acids. For the ratio of sulfates to uronic acids, the correlation coefficient is high at an unreliable level of significance. For other indicators, no significant correlation with age was found. The data obtained allow us to evaluate the correlation between the selected indicators and age as significant. It can be assumed that with age, some accumulation of sialic compounds and γ-globulins occurs in the SF. Obviously, this is a consequence of an increase in the number of glycoproteins, possibly immunoglobulins. One of their biological functions is the utilization of protein breakdown products, which can come from damaged tissues during the involutionary process during aging. We emphasize, however, that we did not find significant differences in the level of these compounds in the SF of people of different ages.

To determine the normative values ​​of the indicators that are most related to age, we assessed the reliability of differences in the concentrations of SA and γ-globulins in different age groups. The distribution of the material into groups was carried out according to the scheme recommended by the symposium on age periodization at the Institute of Age Physiology of the USSR Academy of Medical Sciences. With an increase in these indicators, we did not find significant differences in the groups (Table 4).

Thus, the studies did not reveal significant differences in the indicators of the protein spectrum and carbohydrate-containing compounds of the SF of the knee joints of a healthy person based on gender and age, and the closest correlations with a person’s age were found for indicators of γ-globulins and sialic acids.

Based on the presented literature data, it is easy to notice that with a wide variety of methods and techniques of biochemical research used, the informativeness and diagnostic significance of these studies for practical activities has not been determined.

Bibliographic link

Matveeva E.L., Spirkina E.S., Gasanova A.G. BIOCHEMICAL COMPOSITION OF SYNOVIAL FLUID OF THE KNEE JOINT OF PEOPLE IS NORMAL // Advances in modern natural science. – 2015. – No. 9-1. – pp. 122-125;
URL: http://natural-sciences.ru/ru/article/view?id=35542 (access date: 02/01/2020). We bring to your attention magazines published by the publishing house "Academy of Natural Sciences"

Synovial fluid analysis- laboratory examination of effusion accumulated in the joint cavity. The procedure for taking joint fluid for analysis is called.

A joint is built from two (or more) bones covered at the point of contact with cartilage. The outside is enveloped in a durable and airtight synovial bursa, reinforced with ligaments and tendons. The inside of the synovial bursa is lined with cells that produce synovial fluid. Synovial fluid fills all cavities and cracks in the joint.

Joints allow the body to move as one unit, and joint fluid gives fluidity to movement.

Analysis of joint/synovial fluid It is just as important in the diagnosis of joint diseases, as is a general urine test to identify renal pathology or a general blood test in the diagnosis of anemia.

Synovial fluid is

Synovial or articular liquid or synovial- This is a viscous non-Newtonian fluid, located in the cavity of all joints. Its consistency is similar to egg white (hence it gets its Latin name), and its chemical composition is similar to plasma.

Joint fluid is 20 times thicker than blood!

Compound

• fibroblasts in the synovium produce hyaluronic acid, (total amount 3-4 mg/l)
• lubricin(proteoglycan 4) - lubricates and facilitates gliding of articular surfaces
• interstitial fluid - filtered blood plasma
• enzymes - proteinases and collagenases
• proteins - some come from the blood, some are synthesized directly by the synovium
• , and other components
• cells - a minimum number and single ones to remove microbes and aging cells of the synovial membrane during joint wear

Functions

Joint fluid is a floating lubricant between the cartilage in the joint. It becomes denser with active movement and thinner at rest. Absorbs and reduces impact when running and jumping. Supplies nutrients to cartilage and removes waste products.

Quickly responds to all changes in the joint, acting as an indicator of the pathological process.

Indications

Laboratory examination of joint fluid is necessary for the diagnosis of joint diseases of unknown origin, especially for the differential diagnosis of septic and gouty arthritis, acute monoarthritis.

Symptoms and indications for joint puncture and analysis of synovial fluid:

• joint effusion
• acute or chronic lameness
• an arm or leg does not function as a support due to pain in the joint
• combination with increased body temperature, joint deformation, redness and swelling
• significant

Arthrocentesis

Arthrocentesis or puncture joint- this is a procedure for removing fluid from the joint cavity for subsequent laboratory analysis or for the purpose of treatment - reducing tension and pain, administering medications.

Arthrocentesis during arthrography - a contrast agent is injected into the joint and a series of X-rays are taken. One of the options for the diagnostic use of arthrocentesis. Replaced by more informative CT and MRI.

Arthrocentesis has virtually no contraindications. A relative obstacle to puncture is infection of the skin at the site of future puncture, continued bleeding into the joint, and a general serious condition. N The knee joint is most often punctured, then, as it decreases, the shoulder, elbow, wrist, ankle, and temporomandibular joints are punctured.

No special preparation is needed. It is advisable to refrain from eating 8-10 hours before the procedure.

Before a joint puncture, you must inform your doctor if you are allergic to any medications, especially local anesthetics and iodine. If you are taking blood thinning medications (aspirin, clopidogrel, warfarin), you may need to stop them for several days before the procedure. If necessary, preliminary analysis and analysis are done.

Execution

The skin at the site of the future puncture is disinfected and numbed. The doctor inserts a large puncture needle through the skin and synovium into the joint cavity. The joint fluid is aspirated into a sterile syringe.

The procedure lasts several minutes, after which a pressure bandage is applied to the puncture site.

The syringe with synovial fluid is immediately sent to the laboratory for examination. Less often, they are poured into a test tube with an antiplatelet agent (heparin).

If a test of glucose in the synovial fluid is planned, then a blood sample is taken before arthrocentesis to establish the level of glycemia.

Complications

• joint infection is extremely rare, the risk is higher with repeated punctures
• bleeding into the joint cavity
• pain, cartilage or nerve damage, ligament tear

Synovial fluid is normal

There is normally very little synovial fluid. In the knee joint there is from 0.5 to 4 ml, and in the shoulder joint - up to 3 ml. It is light yellow, transparent, viscous, without impurities.

What are they researching?

• physical properties- quantity, color, transparency, viscosity, pH (acidity)
• chemical parameters- glucose, uric acid,
• stained smear microscopy- total amount of synovial fluid, atypical cells
• microscopy with a polarizing microscope- to identify crystals
• Gram smear microscopy And bacterial sowing on nutrient media - to identify the pathogen and determine its sensitivity to antibiotics

The formation of a mucin clot in acetic acid is not tested. The test is not very informative.

Additionally, complement, enzymes, immunoglobulins, and hormones are examined in the joint fluid.

Complement factors are elevated in rheumatoid arthritis and systemic lupus erythematosus.

Physical properties

Normal synovial fluid transparent, light straw color. When inflamed, it acquires various shades of dull yellow and green. The off-white color is characteristic of crystal-induced arthropathy. Red, brown and orange indicate bleeding into the joint of varying duration, which happens with a blood clotting disorder, trauma, neoplasms, tuberculous arthritis, or treatment with anticoagulants.

The more active the inflammation in the joint, the less transparency.

To determine viscosity A needle is immersed in a drop of synovial fluid and removed. Normally, the length of the resulting tendril-string is more than 5 cm. In case of inflammation, it is less than 5 cm.

Viscosity remains within normal limits in traumatic arthritis, systemic lupus erythematosus, osteoarthritis and pigmented villonodular synovitis. Decreased in acute rheumatic fever, rheumatoid arthritis, gout, pyogenic and tuberculous arthritis.

Rice bodies- this is a destroyed articular membrane covered with fibrin clots, which occurs in rheumatoid arthritis.

Synovial fluid coagulates if it contains fluid that has entered during a puncture or a previous injury. Clots interfere with cell counting, so the joint fluid is poured into a tube with heparin.

pH (acidity) decreases with inflammation.

Chemical analysis

In healthy synovial fluid there is no proteins with high molecular weight (fibrinogen, alpha and beta 2-macroglobulins), and the total amount of protein is 10-30 g/l (or a third of the level in the blood).

Causes of increased protein: ankylosing spondylitis, arthritis, arthropathy in Crohn's disease and ulcerative colitis, gout, psoriatic arthritis, Reiter's syndrome.

Rate level glucose in synovium is possible only if there is data on its concentration in the blood. For this reason, arthrocentesis is performed more carefully, after taking a blood sample.

Normally, synovial fluid contains 0.5 mmol/l less glucose than in the blood. Infectious diseases of the joints reduce glucose by 1.1-5.5 mmol/l compared to blood.

Level uric acid in synovial fluid 356-475 µmol/l, increases with gout.

Lactic acid (lactate) is rarely examined, normally up to 2.7 mmol/l, and in septic arthritis it rises to 55.5 mmol/l.

Lactate dehydrogenase (LDH) is increased in rheumatoid arthritis, infectious arthritis, gout.

Microscopy

When viewing a smear under a microscope, the number and type of cells and crystals in the joint fluid are counted.

Availability crystals in joint fluid is checked using a polarizing microscope. Normally there are none.

Types of crystals in synovial fluid in diseases

• sodium urate - gout
• calcium pyrophosphate - pseudogout
• corticosteroids - after injections of steroids into the joint cavity
• cholesterol - osteoarthritis and rheumatoid arthritis
• hydroxyapatite - calcific periarthritis, osteoarthritis, inflammatory arthritis

Microbiological examination

Culture of synovial fluid is carried out immediately after taking the material.

Decoding the result

The results of the study of synovial fluid are grouped as follows:

• normal- all indicators correspond to the norm
• inflammatory
• Not inflammatory
• septic
• hemorrhagic

Non-inflammatory synovial fluid

• osteoarthritis and degenerative joint diseases
• traumatic arthritis
• chronic gout or pseudogout
• scleroderma
• polymyositis
• systemic lupus erythematosus
• erythema nodosum
• neuropathic arthropathy (Charcot's joint), for example, in diabetes mellitus
• sickle cell anemia
• hemochromatosis
• acromegaly
• amyloidosis

Inflammatory joint fluid

• rheumatoid arthritis
• reactive arthritis
• psoriatic arthritis
• acute rheumatic fever
• acute gout or pseudogout
• scleroderma
• polymyositis
• systemic lupus erythematosus
• ankylosing spondylitis
• inflammatory bowel diseases
• viral, fungal, bacterial infection in the joint, Lyme disease
• acute attack of gout

Septic changes

• purulent bacterial infection
• septic arthritis

Hemorrhagic joint fluid

• injury
• tumors
• hemophilia and other coagulopathies - increased bleeding due to deficiency of one of the coagulation factors
• severe vitamin C deficiency (scurvy)
• Ehlers-Danlos syndrome
• neuropathic arthropathy

Joint puncture and synovial fluid analysis was last modified: December 1st, 2017 by Maria Bodyan

Synovial fluid is one of the main organ-specific components of each joint, which largely determines its morphofunctional state. Synovial fluid performs metabolic, locomotor, trophic and barrier functions, which play an important role in ensuring the normal physiology of the joint and its connection with other tissues.

Synovial fluid reflects the processes occurring in the cartilage and synovial membrane, and subtly responds to disorders in the joint by changing its physicochemical characteristics and cellular composition. That is why laboratory testing of synovial fluid is of fundamental importance in the diagnosis of joint diseases. In some cases, examination of synovial fluid is the first, and sometimes the only necessary diagnostic test. 

Pre-analytical precautions
Normally, the amount of synovial fluid in the joint is small, but with joint diseases, its volume increases - joint effusion is formed.

It is obtained for analysis by joint puncture (arthrocentesis). During the procedure, local anesthetics are used, but the use of procaine is undesirable, as it causes cell destruction. Since synovial fluid often forms a clot, for cytological examination it is recommended to obtain it with an anticoagulant, the best of which is the sodium salt EDTA.

Synovial fluid is distributed into 3 tubes:
into a test tube with an anticoagulant for cytological examination;
in a dry test tube for chemical microscopic examination and preparation of a native preparation for microscopy in polarized light;
into a sterile tube for bacteriological research.

On the referral form for testing synovial fluid in the laboratory, the doctor must indicate the patient’s full name, as well as the clinical diagnosis. This may help in identifying unusual particles in synovial fluid.

Analysis of synovial fluid should be carried out as soon as possible from the moment it is obtained.

False results may be obtained if the test is delayed by more than 6 hours as a result of the following changes:
decrease in the number of leukocytes;
reducing the number of crystals (calcium pyrophosphate dihydrate);
the presence of artifacts in the form of new crystal formations.

If necessary, it is permissible to store synovial fluid in a syringe with a minimum amount of air in the refrigerator for 1 day without significantly changing its parameters. Longer storage is possible in the freezer at a temperature of -70 °C.

Laboratory practice
Standard laboratory testing of synovial fluid includes the following steps:
assessment of physical properties (volume, color, character, viscosity, turbidity, pH, mucin clot);
cytological examination (counting the number of cells, microscopy of native and stained specimens);
polarization microscopy of the native drug;
chemical analysis;
additional studies (if indicated).

PHYSICAL PROPERTIES
The volume of synovial fluid is assessed using a graduated test tube, color and character - visually in transmitted light in comparison with distilled water.

Viscosity is determined by a hemoviscometer or by the length of a thread trailing a glass rod after it is immersed in a test tube and is expressed in conventional units:
1 - high viscosity;
2 - moderate viscosity;
3 - extremely low viscosity (close to water).

To assess turbidity, a score is used:
1 point - complete transparency;
2 points - slight turbidity;
3 points - turbidity.

A mucin clot is formed when synovial fluid is mixed with acetic acid. Depending on the composition of the synovial fluid, the clot can be dense or loose. To determine pH, diagnostic strips are used, usually used for urine testing. This indicator must be determined immediately after receiving synovial fluid (the pH changes during storage).

CYTOLOGICAL RESEARCH
Counting cells in synovial fluid, which is carried out according to generally accepted rules (manual or automatic), is of significant diagnostic importance. Normally, cytosis is no more than 100 cells in 1 μl. Storing synovial fluid for several hours at room temperature leads to the destruction of white blood cells.

Both native and colored preparations are subjected to microscopic examination. The technique for its preparation is standard; the use of a cytocentrifuge is recommended. The study of the native drug makes it possible to roughly estimate the content of cellular elements, identify ragocytes and non-cellular particles. In a stained preparation, a cytogram (synoviocytogram) is calculated for 100-200 cells, preferably in 2-3 preparations. Contrary to the well-known opinion that cells of tissue origin in the synovial fluid predominate over the formed elements of blood, often the cellular composition of the effusion is represented predominantly by neutrophils and lymphocytes.

In arthritis, special forms of neutrophils - ragocytes - can be found in the synovial fluid. Their cytoplasm contains inclusions of immune complexes, which gives the cell a “cellular” appearance (vacuolation in the form of a bunch of grapes).

POLARIZATION MICROSCOPY
Polarizing microscopy is used to identify crystals.

To successfully identify crystals, a number of conditions must be met:
exclusion of contamination of the synovial fluid sample;
eliminating the use of EDTA, which dissolves crystals;
use absolutely clean pipettes, test tubes and slides.

Work should be carried out in a dust-free work area. The main condition is the presence of a polarizing microscope with good optics. To prepare the drug, a small drop of well-mixed synovial fluid is applied to the glass, which is covered with a coverslip (make sure that no air bubbles form). It is optimal to study two drugs. Microscopy is performed at low magnification, then at 1000x magnification. Sodium urates (MSUM) appear in the form of long needles or bundles measuring 1-20 microns, they are clearly visible on a black background as white “sparks” due to birefringence. Often detected in neutrophils, where their number increases significantly during acute attacks of gout. Calcium dehydrogen pyrophosphate (CPPD) crystals come in a variety of shapes (usually rectangles or diamonds with blunt ends) and very small sizes (less than 2 microns in diameter). They are slightly less visible due to the weak glow. Since the main purpose of examining synovial fluid is to exclude an infectious process, it is necessary to perform Gram staining of smears (which does not exclude the need for bacteriological examination).

CHEMICAL ANALYSIS
Protein and glucose are determined by methods that are used in clinical practice to determine protein and glucose in urine. Diagnostic strips can be used for semi-quantitative assessment. For severe purulent arthritis, lactate determination is recommended.

QUALITY ASSURANCE AND CONTROL
There is high variability in the results of synovial fluid analysis between different laboratories. There are no specific approaches to organizing quality control in the study of synovial fluid. An important condition is the standardization of technology for laboratory analysis of synovial fluid.

When diagnosing gout, the concentration of uric acid in the synovial fluid is determined (as well as in the blood plasma). The determination of autoantibodies (primarily rheumatoid factor and autoantibodies to DNA) is conveniently performed by the latexagglutination method.

Clinical and diagnostic value
With pathology, the color of the synovial fluid changes depending on the nature of the joint effusion (serous, hemorrhagic, fibrinous, mixed). With secondary synovitis, the synovial fluid becomes amber in color, and with rheumatoid and psoriatic arthritis, the color varies from yellow to green. The yellow-green color of the synovial fluid can be due to infectious and gouty lesions of the joints. In case of septic or traumatic damage to the joint, the synovial fluid acquires a bloody color of varying degrees of severity. In pigmented villous nodular synovitis, the joint effusion is brownish-red in color. The creamy nature of synovial fluid can be caused by fats in intra-articular fractures. The golden hue of synovial fluid is due to the presence of cholesterol.

Turbidity is characteristic of rheumatoid, psoriatic or septic arthritis. The viscosity of synovial fluid decreases in rheumatism, rheumatoid, gouty and psoriatic arthritis, Reiter's disease, arthrosis, ankylosing spondylitis, and to a lesser extent in post-traumatic arthritis. A loose mucin clot always indicates the presence of an inflammatory process in the joint (rheumatoid arthritis and other diseases), but there are more advanced indicators of it.

Changes in the pH of synovial fluid have no fundamental diagnostic value; its value decreases with inflammation. Microscopy of a native drug can reveal non-cellular particles - exogenous (plant spines, fragments of artificial crystals, components of endoprostheses, drug suspensions) and endogenous (fragments of cartilage, menisci, ligaments, crystals) components. The appearance of endoprosthesis components in the synovial fluid is a prognostic sign of the development of its instability. Among the endogenous components of synovial fluid, the most important element, which has fundamental clinical and diagnostic significance, is crystals of sodium urate and calcium pyrophosphate. Amyloid bodies, drops of neutral fat, crystals of cholesterol, calcium, and hematoidin can be detected in the synovial fluid. 

Cytosis is one of the most sensitive diagnostic criteria, allowing to differentiate inflammatory and non-inflammatory diseases and assess the dynamics of the pathological process. An increase in the number of leukocytes in the synovial fluid is characteristic of the acute period of any inflammatory arthritis (for example, during an attack of gout, the number of leukocytes reaches 60x106 cells in 1 μl). Moderate cytosis was observed in pseudogout, Reiter's syndrome, and psoriatic arthritis. In infectious (bacterial) arthritis, cytosis is usually higher (50x103 cells in 1 μl), and microflora growth is detected in such samples. Small cytosis (less than 1-2x103 cells in 1 μl, predominantly neutrophils) is characteristic of “mechanical” joint damage, including microcrystalline arthritis.

In rheumatoid arthritis, the granulocyte content reaches 90%, and the number of lymphocytes decreases to less than 10%. These changes are more pronounced in the seropositive version of rheumatoid arthritis. In toxic-allergic synovitis, synovial form of tuberculosis or arthritis of a paraneoplastic nature, mononuclear cells predominate in the synovial fluid.

The presence of ragocytes in significant numbers is characteristic of rheumatoid arthritis. Single ragocytes can also occur in other joint lesions (septic arthritis and inflammatory arthropathy). LE cells are found in the synovial fluid of systemic lupus erythematosus in approximately 50% of patients. Atypical cells in synovial fluid are recorded relatively rarely.

Bacterioscopy has only an auxiliary and often very limited value, since if the microbial nature of the inflammation is suspected, a standard bacteriological examination is necessary. However, microscopy of a smear of synovial fluid may reveal gonococci in gonococcal arthritis. The presence of gram-positive cocci in clusters in smears suggests a staphylococcal etiology of the infection. Other causative agents of infectious arthritis may be streptococci and gram-negative bacilli. In case of fungal arthritis (candidiasis, aspergillosis), fungal mycelium is detected in the synovial fluid. The level of protein in synovial fluid increases slightly in degenerative diseases and post-traumatic arthritis. A more pronounced increase in the content of total protein is observed in inflammatory diseases (for example, in rheumatoid arthritis - up to 70 g/l), and its qualitative composition often changes.

Another important parameter characterizing the condition of the synovial fluid is the glucose level. This is a more specific, but less sensitive indicator of inflammatory changes in the joint, since the level of glucose in the synovial fluid is markedly reduced in inflammatory arthropathy. That is why in recent years, for the express diagnosis of purulent (septic) arthritis, the level of lactate in the synovial fluid is determined. Changes in the composition of synovial fluid make it possible to establish the inflammatory nature of the disease that led to the formation of joint effusion. Neutrophilic leukocytosis, an increase in protein and lactate concentrations, as well as a decrease in glucose levels are important signs of an inflammatory process in the joint. Immunological methods also make it possible to differentiate inflammatory and non-inflammatory joint diseases. Autoantibodies appear in synovial fluid earlier than in blood plasma.

The procedure, which is called “study of synovial fluid,” is necessary for diagnosing a variety of dystrophic and inflammatory diseases of the joints.

Synovial fluid is an exudate produced by the articular membrane, consisting of connective tissue and lining the bone and cartilage surfaces. It performs the following functions in the joint:

• locomotor;
• metabolic;
• barrier;
• trophic.

The joint fluid quickly reacts to all inflammatory processes that occur in the joint, synovium and cartilage tissue. This substance is one of the most important articular components, which determines the morphofunctional state of the joint.

In a normal, healthy joint, the volume of fluid is moderate. But with the development of certain joint ailments, a so-called joint effusion is formed, which is subject to investigation. More often than others, a sample of synovial fluid from large joints (elbows, knees) is analyzed.

Synovial fluid can be obtained using a puncture. The most important condition when taking a puncture is the sterility of the joint.

A standard analysis of a synovial fluid sample includes:

1. Macroscopic analysis of punctured fluid (color, volume, turbidity, viscosity, mucin clot).
2. Counting the number of cells.
3. Microscopy of the native drug.
4. Cytological analysis of the stained preparation.

In a healthy person, synovial fluid is light yellow (straw) in color. However, in both arthritis and ankylosing spondylitis (), the color of the test fluid remains yellow. During inflammatory processes, the color of the joint fluid may become different, depending on the characteristic changes in the synovial membrane.

In the presence of psoriatic or rheumatoid arthritis, the color of the examined exudate may vary from yellow to green. In traumatic or bacterial diseases, the color of the synovial fluid ranges from burgundy to brown.

The synovial fluid of a healthy joint is clear, but in the presence of psoriatic, rheumatoid or septic arthritis, it becomes cloudy.

The nature of viscosity depends on:

1. pH level;
2. salt concentration;
3. the presence of previously administered drugs;
4. degree of polymerization of hyaluronic acid.

An increased level of viscosity is observed when:

• systemic lupus erythematosus;
• various traumatic changes.

A decrease in viscosity indicators is observed when:

1. rheumatism;
2. arthrosis;
3. ankylosing spondylitis;
4. various arthritis (psoriatic, gouty, rheumatoid).

One of the most important features of synovial fluid is the ability to produce a mucin clot when mixed with acetic acid.

In this case, the presence of a loose clot indicates inflammatory processes occurring in the joints.

The main analysis that determines the pathology of the joint

The main study diagnosing a particular pathology is a microscopic analysis of a sample of synovial fluid.

First of all, doctors pay attention to counting the number of cells in the drug. The norm is up to 200 cells/μl. A significant increase in the number of cells is called cytosis. Cytosis makes it possible to diagnose dystrophic and inflammatory diseases and clearly assess the development of inflammatory processes.

During the acute stage of any type of arthritis, the patient experiences pronounced cytosis (the number of cells ranges from 30,000 to 50,000).

1. With microcrystalline arthritis, the patient exhibits slight cytosis.
2. In Reiter's syndrome, pseudogout or psoriatic arthritis, the cytosis is moderate (20,000 to 30,000 cells).
3. If the cell count exceeds 50,000, the patient is diagnosed with bacterial arthritis.

Careful analysis can reveal the presence of a large number of different crystals in a patient, but only two types are important for diagnosis. In pseudogout, the patient has calcium dihydrogen pyrophosphate crystals, and the presence of sodium urate crystals indicates gout. These deposits can be detected using polarizing microscopy.

Healthy synovial fluid contains blood elements (lymphocytes, monocytes, neutrophils) and various tissue cells (histiocytes, synoviocytes).

During inflammatory processes, a special form of neutrophils, ragocytes, can be found in joint exudate. Such cells have a cellular structure formed due to the inclusion of immune complexes in the cytoplasm. The presence of ragocytes mainly indicates rheumatoid arthritis.

The detection of mononuclear cells in the synovial fluid is characteristic of tuberculous processes, allergic synovitis and arthritis that have developed against the background of neoplasms.

It is worth noting that inflammatory joint diseases are characterized by an increase in acute phase parameters and lactate dehydrogenase levels.

Microscopic examination of the smear can detect gram-positive cocci, chlamydia or gonococci. Fungal bacteria are often detected in patients. To accurately determine the nature of the infectious process and establish sensitivity to antibiotics, doctors culture the synovial fluid for pathogenic microflora.

Puncture of joint exudate can only be performed as prescribed by a rheumatologist. In conclusion, the video in this article will raise the very interesting issue of synovial fluid replacement.

[02-049 ] Microscopic examination of synovial fluid

635 rub.

Order

A study of synovial fluid with a description of its physicochemical properties and characteristics of cellular elements, which is carried out for the diagnosis of various inflammatory diseases of the joints and degenerative processes.

Synonyms Russian

• Joint puncture
• Diagnosis of arthritis

SynonymsEnglish

• Microscopic examination of synovial fluid
• Synovial fluid examination - Pathology Test

Methodresearch

Microscopy.

What biomaterial can be used for research?

Synovial fluid.

General information about the study

The analysis is indicated for patients with damage to one or more joints of unknown origin, manifested by joint pain and swelling, in the case where the study of synovial fluid (SF) will help in making a diagnosis. The analysis includes determination of the physicochemical properties of the liquid and microscopic examination of cellular elements. The most serious reason for its use is the need to exclude an infectious process in the joint. In cases of inflammation, synovial fluid often collects in the upper articular floor, forming a “joint effusion.” Synovial fluid is taken by puncture of the joint. Infectious complications are extremely rare.

Synovial fluid serves as a “lubricant” for cartilage and ligaments. By changes in its cellular composition and physicochemical properties, one can judge pathological processes in the joint. For example, it is known that synovial fluid in joints affected by osteoarthritis has lower viscosity and elasticity than synovial fluid in healthy joints.

In particular, one of the criteria for such an inflammatory joint disease as gout is the detection of uric acid crystals in the synovial fluid. Moreover, the determination of uric acid in synovial fluid has a greater prognostic value than the analysis of blood serum, since the concentration of uric acid in the serum during an acute attack can be within normal limits, and uric acid crystals in synovial fluid are detected even in the interictal period.

In patients with rheumatoid arthritis, examination of synovial fluid is of great importance to confirm the diagnosis and determine the local activity of the inflammatory process. In rheumatoid arthritis, the number of leukocytes in the synovial fluid increases to 25,000 per 1 μl due to neutrophils (25-90%), the protein content reaches 40-60 g/l. In the cytoplasm of leukocytes, inclusions and vacuoles similar to a bunch of grapes (ragocytes) are found. These cells contain phagocytosed material - lipid or protein substances, rheumatoid factor, immune complexes, complement. Ragocytes are also found in other diseases - rheumatic, psoriatic arthritis, systemic lupus erythematosus, bacterial arthritis, gout - but not in such quantities as in rheumatoid arthritis.

The most pronounced changes in synovial fluid are found in bacterial arthritis. Externally, synovial fluid may look like pus; the cell content reaches 50,000-100,000 in 1 μl, of which neutrophils make up more than 80%. Sometimes in the first 24-48 hours of acute arthritis, the number of cellular elements may be less than 25,000 in 1 μl.

What is the research used for?

• For diagnosis (including differential) of joint diseases,
• to evaluate the effectiveness of extra- and intra-articular therapy,
• in order to establish the degree of local inflammatory activity and the nature of the inflammatory process,
• to monitor the dynamics of the pathological process in the joints.

When is the study scheduled?

• When recognizing joint diseases and the characteristics of their course, when there is synovial fluid in excess quantities: with severe pain in the joints and difficulty moving, visible damage to the joint (swelling).

What do the results mean?

In a healthy joint, synovial fluid is clear. With rheumatoid, psoriatic or septic arthritis, it becomes cloudy.

The normal color of the liquid is light yellow. During inflammation, it changes depending on the nature of the changes in the synovial membrane, for example, with rheumatoid and psoriatic arthritis, the color ranges from yellow to green.

The normal number of cells in the preparation is up to 200 cells/μl. An increase in the number of cells (cytosis) makes it possible to differentiate inflammatory and dystrophic diseases and assess the dynamics of the inflammatory process. Pronounced cytosis (30,000 - 50,000) is characteristic of the acute period of inflammation in any arthritis, moderate cytosis (up to 20,000 - 30,000) is noted in pseudogout, Reiter's syndrome, psoriatic arthritis. Slight cytosis is characteristic mainly of microcrystalline arthritis. A cell count of more than 50,000 in most cases indicates the presence of bacterial arthritis.

A large variety of crystals can be identified in synovial fluid. However, only two types of them are of diagnostic value. Sodium urate crystals are a sign of gout, and calcium dihydrogen pyrophosphate crystals are found in pseudogout. These crystals can be identified by polarization microscopy.

Normally, cells of tissue origin (synoviocytes, histiocytes), as well as blood elements, are found in the synovial fluid. These are predominantly lymphocytes, less often neutrophils and monocytes. During inflammation, special forms of neutrophils, ragocytes, can be found in the synovial fluid. Their cells have a “cellular” appearance due to the inclusion of immune complexes in the cytoplasm. These are the most characteristic signs of rheumatoid arthritis. In some conditions (allergic synovitis, tuberculosis, arthritis against the background of neoplasms), mononuclear cells predominate in the synovial fluid.

Changes in synovial fluid in various pathological processes

Sign	Type of changes
	Non-inflammatory	Inflammatory	Septic
	Straw yellow		Varies
Transparency	Transparent	Translucent
Leukocytes, in 1 µl		2 000 – 75 000
Neutrophils, %
Crystals
Bacteriological research	Negative	Negative	Sometimes positive
Diseases	Osteoarthrosis, traumatic arthrosis, aseptic necrosis, systemic lupus erythematosus	Rheumatoid arthritis, gout, pseudogout, systemic lupus erythematosus, seronegative spondyloarthropathy	Gonococcal arthritis, tuberculous arthritis, infectious arthritis (staphylococcal and streptococcal)

Changes in synovial fluid in arthritis and arthrosis



Important Notes

• The final conclusions for making a diagnosis must be made based on a comprehensive accounting of all data, including a comparison of the results of laboratory tests and the clinical picture as a whole.

• Detection of the histocompatibility gene HLA-B27. Determination of predisposition to the development of spondyloarthropathies (including ankylosing spondylitis - ankylosing spondylitis)

Who orders the study?

Orthopedist, surgeon, rheumatologist, arthrologist.

Literature

• Tercic D & Bozic B: The basis of the synovial fluid analysis. Clin Chem Lab Med 2001; 39(12):1221–1226.
• Garcia-De La Torre I: Advances in the management of septic arthritis. Rheum Dis Clin North Am 2003; 29:61-73.
• Zakharova M.M. Synovial fluid studies. In the book: Rheumatology. National guidelines. Ed. Academician of the Russian Academy of Medical Sciences E.L. Nasonov and Academician of the Russian Academy of Medical Sciences V.A. Nasonova. M., "GEOTAR-Media", 2008, p. 62-66.