The composition of the synovial fluid is normal. Microscopic examination of synovial fluid. Bacteriological examination of synovial fluid

General clinical examination of joint fluid includes determination of the physicochemical properties of the fluid and microscopic examination of cellular elements. Reference parameters of synovial fluid are presented in the table.

Table Reference indicators of synovial fluid

The study of synovial fluid plays an important role in clarifying the nature of the process in the affected joint. Indications for joint puncture: monoarthritis of unknown etiology, discomfort in the affected joint (if the diagnosis has been established), the need to monitor the effectiveness of treatment for infectious arthritis, for the differential diagnosis of arthritis and arthrosis, since the choice of a program for further examination and treatment of the patient depends on this. Indicators of synovial fluid in arthritis and arthrosis are presented in the table.

Table Changes in synovial fluid in arthritis and arthrosis

In clinical practice, joint damage is most often detected in the following diseases.

Infectious arthritis is divided into gonococcal (arising as a result of dissemination of gonococcal infection) and non-gonococcal - most often caused by Staphylococcus aureus (70% of cases) and Streptococcus, as well as many viral infections (especially rubella, infectious mumps, infectious mononucleosis, hepatitis) and Lyme disease , caused by the spirochete Borrelia burgdorferi, transmitted by tick bites. Septic arthritis can be caused by fungi and mycobacteria.

Synovitis caused by crystals. Crystal deposition in joints or periarticular tissues underlies gout, pseudogout and apatite disease. To diagnose gout and pseudogout, polarization microscopy of the sediment obtained by centrifugation of synovial fluid is performed. Use a polarizing microscope with a red filter. The needle-shaped urate crystals characteristic of gout glow yellow (if their long axis is parallel to the axis of the compensator) and have strong negative birefringence. They are found both in synovial fluid and in neutrophils. Crystals of calcium pyrophosphate dihydrate, detected in pseudogout, have a variety of shapes (usually diamond-shaped), glow blue and are characterized by a weak positive double reflex

laziness. Complexes containing hydroxyapatite (specific for apatite disease), as well as complexes containing basic calcium and phosphorus salts, can only be detected using electron microscopy. It should be emphasized that hyperuricemia should not be considered a specific sign of gout, and calcification of the joints - pseudogout; in any case, a polarization microscopy study is necessary to confirm the diagnosis.

Rheumatoid arthritis. If inflammation of one joint is clearly predominant, a study of the synovial fluid should be performed to exclude an infectious genesis of its origin, since rheumatoid arthritis predisposes to infectious arthritis.

Spondyloarthropathy. This group includes a number of diseases that are characterized by asymmetric oligoarthritis. Synovial fluid examination is performed to exclude septic arthritis. The following spondyloarthropathies are distinguished.

■ Ankylosing spondylitis. Of the peripheral joints, the hip and shoulder joints are most often affected.

■ Arthritis in inflammatory bowel diseases: 10-20% of patients suffering from Crohn's disease and ulcerative colitis develop joint damage, especially often the knee and ankle.

■ Reiter's syndrome and reactive arthritis developing after urogenital or intestinal infections.

■ Psoriatic arthritis develops in 7% of patients with psoriasis.

SCV. Changes in the joint fluid can be both non-inflammatory (arthrosis) and inflammatory (arthritis).

Osteoarthritis is a degenerative disease of the joints, characterized by the “wear and tear” of articular cartilage with subsequent bone growths along the edges of the articular surfaces.

Changes in synovial fluid during various pathological processes are reflected in the table.

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.

In patients with rheumatoid arthritis, examination of synovial fluid is important 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, SLE, bacterial arthritis, gout, but not in such quantities as in rheumatoid arthritis.

Table Changes in synovial fluid in various pathological processes

Why perform a synovial fluid analysis?

In primary care situations, synovial fluid (SF) analysis can help determine the specialist to whom the patient should be referred.

If the GS is non-inflammatory, see an orthopedist.
If it’s inflammatory, see a rheumatologist.

Diagnostic value of synovial fluid analysis

Inflammatory or non-inflammatory pathology
Crystalline inflammation or sepsis, or exacerbation
Helps identify groups of diseases based on cell number and cell type
Determination of the type of prosthetic failure
Prognostic value
Orthopedic intervention
Stage of specific disease
Therapy monitoring. In particular, refusal of monoclonal antibody therapy.

In Fig. 1 and 2 reflect the algorithm for diagnosing joint diseases based on data from the analysis of synovial fluid

Pathological changes in the tissues surrounding the diseased joint are reflected in the volume, cellular composition and presence of solid particles in the fluid. Inflammatory joint diseases, differing in etiology, have characteristic cellular patterns that can be recognized and used in the diagnosis of a specific disease or group of diseases (Fig. 1, 2). In order to identify these differences, it is necessary to correctly select and properly store SF in order to minimize autolytic changes and degradation of characteristic cells. EDTA is used as an anticoagulant. Storage at 4°C is well tolerated by SF and gives excellent diagnostic results. Almost adequate results can be obtained up to 48 hours from aspiration, but longer storage, even at 4°C, usually allows only crystals and particles to be identified. Most cells undergo lysis.

Cytological analysis of synovial fluid

Fat cells can be found in the analysis of the SF of most patients with joint disease, but most often they are observed in inflammatory arthritis in patients with seronegative spondyloarthropathies and in non-inflammatory joint lesions associated with trauma.

This type of CL is often detected when analyzing the SF of patients with intra-articular hemorrhage or arthrography, as well as in allergic reactions to injected drugs, such as artificial SF.

General clinical examination (analysis) of joint fluid includes determination of the physicochemical properties of the fluid and microscopic examination of cellular elements.

Macroscopic characteristics of synovial fluid (color, degree of turbidity and viscosity) are assessed in transmitted light. Viscosity is assessed by the length of the mucin filament: the length of the filament formed by a drop released from a syringe should normally be more than 3 cm. With inflammation, the viscosity decreases, and accordingly the length of the filament decreases.

The manipulation is performed with the patient sitting with the arm lowered along the body and lying on the knee. The needle is inserted from the front, its end is directed slightly downward and laterally, towards the coracoid process of the scapula; the needle moves posteriorly, towards the articular surface of the scapula. It is also possible to puncture the shoulder joint through a posterior approach.

The patient bends the arm at the elbow joint at an angle of 60°, the wrist is in a pronated position. The needle insertion point is located on the lateral surface of the joint, between the lateral epicondyle of the humerus and the radius.

The knee joint and its periarticular bursae can be punctured with the patient in the supine position, with the lower limb extended at the knee joint. A needle, usually 0.8 mm in diameter, is inserted from the lateral side just below the caudal edge of the patella. As an alternative, it is possible to insert the needle from the medial side, also under the caudal edge of the patella.

Macroscopic characteristics make it possible in many cases to distinguish between non-inflammatory, inflammatory and infectious effusions. In addition, there may be blood in the joint fluid. The appearance of the effusion suggests a certain disease. So-called non-inflammatory effusions actually correspond to pathological processes characterized by mild to moderate inflammation, such as osteoarthritis.

Laboratory studies of intra-articular fluid include counting cells and assessing their qualitative composition, microbiological examination (if an infectious process is suspected), as well as microscopic examination of the native drug to identify various cells and crystals. However, the choice of a particular test depends on the suspected diagnosis.

Reference indicators (normal) of synovial fluid

The study of synovial fluid plays an important role in clarifying the nature of the process in the affected joint.

Indications for joint puncture: monoarthritis of unknown etiology, discomfort in the affected joint (if the diagnosis has been established), the need to monitor the effectiveness of treatment for infectious arthritis, for the differential diagnosis of arthritis and arthrosis, since the choice of a program for further examination and treatment of the patient depends on this.

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. The consistency is similar to egg white (hence it gets its Latin name), and the 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.

Performance

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.

For determining viscosity A needle is immersed in a drop of synovial fluid and removed. Normally, the length of the resulting tendril-thread 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 tested, 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

The joint fluid is called synovial fluid (SF) or synovium because of its similarity to egg white: syn (like), ovia (egg). It is a viscous, colloidal substance that fills the cavity in movable joints. Analysis of the joint fluid is of paramount importance in the diagnosis of orthopedic and rheumatological joint diseases (JDs). Aspiration of joint fluid (sampling with a syringe) is indicated for any patient with joint effusion or joint inflammation. Aspiration of asymptomatic fluid is useful in patients with gout and pseudogout, since fluid in these diseases contains crystals formed by various salts.

PHYSIOLOGY AND COMPOSITION OF SF

All movable (synovial) human joints are lined with tissue called synovium, and their cavity is filled with fluid. This is an ultrafiltrate of blood plasma from the vessels of the synovial membrane, supplemented with hyaluronic acid (HA), which is produced by cells of the synovial membrane - synoviocytes B (synoviocytes A - macrophages). SF is a viscoelastic fluid that lubricates joints, nourishes cartilage, and forms shock-absorbing cushions that allow bones to move freely and withstand impacts.

Macroscopic analysis of fluid fluid in joint diseases

Volume Analysis SJ

The amount of fluid in the joints is usually 0.15 – 4.0 ml. The knee joint usually contains up to 4 ml of fluid. An increase in the volume of the SF is a diagnostic indicator of joint disease; the volume of the SF can exceed 25 ml.

Color and Transparency Analysis

Normal SF is colorless and transparent (Fig. 1). Other manifestations may indicate various diseases.

Yellow color and clear fluid are typical of non-inflammatory effusions, while yellow color and cloudiness of fluid are typically associated with inflammatory processes.

The white color and turbidity of the fluid is due to the crystals it contains.

Red, brown, or xanthochromic (yellowish) indicate bleeding into the joint.

A cloudy or opaque appearance of SF usually indicates increased cell concentration, crystal content, or the presence of lipids. Microscopic studies are needed to find out.

Inclusion analysis

In addition, synovium may contain various types of inclusions. Free-floating tissue aggregates appear as rice bodies. Rice bodies are observed in rheumatoid arthritis (RA) and are the result of loss of fibrin strands (Fig. 2).

Grayish-brown debris is shards of metal and plastic from the wear of the prosthesis. These inclusions look like ground pepper.

Viscosity Analysis

Synovium is very viscous due to the high concentration of hyaluronic acid biopolymer in combination with proteins (mucin). To assess the viscosity of the fluid, a thread test is used. When pouring fluid from a syringe into a test tube, fluid with normal viscosity forms threads (until the drop breaks) of about 5 cm (Fig. 3, a). Liquid with poor viscosity will form shorter drops or flow down the wall of the test tube like water (Fig. 3, c). The viscosity of the fluid depends on the concentration of hyaluronic acid (HA). During inflammation, the viscosity of the fluid decreases. Firstly, the permeability of the vessels of the synovium increases and the fluid is diluted with plasma; secondly, the synthesis of hyaluronan by type B synoviocytes decreases, and thirdly, the synthesis of enzymes that destroy HA increases.

Coagulation of synovial fluid

The presence of fibrinogen in it can cause clotting of the fluid. Fibrinogen enters the synovial fluid when the synovial capsule is damaged by trauma. Blood clots in the sample interfere with the blood cell count. Preliminary introduction of lithium heparin into the test tube for the SF sample avoids clotting of the SF. Therefore, SF coagulation is an indicator of joint injury.

Mucin clot test

The mucin clot test in the diagnosis of joint diseases allows you to assess the integrity of the HA-protein complex (mucin). Normal SF forms, when an aliquot is added to 2% acetic acid, a dense white precipitate in a transparent medium (Fig. 4). An easily disintegrating clot in a turbid environment reflects low levels of hyaluronic acid. The nature and amount of sediment varies from good to weak and reflects the quantity and quality of the protein/hyaluronan complex. In inflammatory joint diseases, the release of hydrolytic enzymes into the liquid leads to the disintegration of these complexes and poor sediment formation. Non-inflammatory arthropathy produces a good mucin deposit. Bleeding dilutes the synovial fluid and prevents the formation of a good mucin clot.

Chemical analysis of synovial fluid in joint diseases

Protein Analysis and Disease

Synovium contains all the proteins found in plasma, with the exception of high molecular weight proteins. These are fibrinogen, beta-2 macroglobulin and alpha-2 macroglobulin. These proteins may be absent or present in very small quantities. The protein content in SF is determined by the same methods as in blood serum. The normal range for protein in synovial fluid is 1-3 g/dL. Elevated protein levels are observed in joint diseases such as ankylosing spondylitis, arthritis, arthropathy that accompany gout, psoriasis, Reiter's syndrome, Crohn's disease and ulcerative colitis.

Glucose analysis in disease diagnosis

SF glucose levels are interpreted using serum glucose levels. Joint puncture is done on an empty stomach or at least 6-8 hours after eating. Typically, synovial fluid glucose levels are 10 mg/dL lower than serum levels. In case of infectious joint damage, the glucose level in the SF is lower than in the serum by 20 -200 mg/dl.

Uric acid analysis in the diagnosis of diseases

In synovial fluid, urate usually ranges from 6 to 8 mg/dL. The presence of uric acid (UA) in SF helps in the diagnosis of gout. MK crystals are identified in polarized light. Laboratories where there is no polarizing microscope use a biochemical method to analyze UA in SF.

Lactic acid diagnostics of diseases

Lactic acid is rarely measured in synovial fluid but may be useful in the diagnosis of septic arthritis. Typically, lactate in synovial fluid is less than 25 mg/dL, but in septic arthritis it can reach 1000 mg/dL.

Lactate dehydrogenase in the diagnosis of diseases

Analysis of lactate dehydrogenase (LDH) activity in normal SF and in SF with joint pathology showed that while its level in the serum remains normal, enzyme activity in SF usually increases with joint damage from RA, infectious arthritis and gout. Neutrophils, the content of which increases during the acute phase of these diseases, contribute to the increase in LDH.

Rheumatoid factor in the diagnosis of diseases

Rheumatoid factor (RF) is an antibody to immunoglobulins. RF is present in the serum of most patients with RA joint disease, while it is detected in the synovial fluid of only half of these patients. However, if RF is formed in the synovial fluid, it can be positive in the synovium and negative in the blood serum. In chronic inflammatory diseases, the Russian Federation is false positive.