Synovial fluid analysis provides diagnostic information for patients with joint infections or crystal-induced arthritis. Synovial fluid is normally clear and viscous, but abnormal fluids can be categorized as noninflammatory, inflammatory, septic, or hemorrhagic based on analysis. Key components of analysis include white blood cell count, differential count, cultures, Gram stain, and crystal search using polarized light microscopy. Abnormal findings help reduce the number of possible joint effusion causes to consider in the differential diagnosis.

1. SYNOVIAL FLUID:NORMAL
PHYSIOLOGY AND PATHOLOGY

2. Synovial fluid is a viscous fluid found in the
cavities of synovial joint
"synovial" partially derives from ovum,(egg)
• The principal role of synovial fluid is to reduce
friction between the articular cartilage of
synovial joints during movement.
• It also provides nutrition to the articular
cartilage and disc

4. GENERATION AND CLEARANCE OF
SYNOVIAL FLUID
• The Starling equation reads as follows:
• J= K ([Pc − Pi] − σ[πc − πi])
• ([Pc − Pi] − σ[πc − πi]) is the net driving force,
• Kf is the proportionality constant, and
• Jv is the net fluid movement between
compartments.

5. • According to Starling's equation, the
movement of fluid depends on six variables:
• Capillary hydrostatic pressure ( Pc )
• Interstitial hydrostatic pressure ( Pi )
• Capillary oncotic pressure ( πc )
• Interstitial oncotic pressure ( πi )
• Filtration coefficient ( Kf )
• Reflection coefficient ( σ )

6. • Synovial fluid is a mixture of a protein-rich
ultrafiltrate of plasma and hyaluronan
synthesized by synoviocytes.
• Generation of this ultrafiltrate depends on the
difference between intracapillary and intra-
articular hydrostatic pressures and between
colloid osmotic pressures of capillary plasma
and synovial tissue fluid

7. • Proteins are present in synovial fluid at
concentrations inversely proportional to
molecular size, with synovial fluid albumin
concentrations being about 45% of those in
plasma
• Synovial fluid is cleared through lymphatics in
the synovium, assisted by joint movement

8. • Normal synovial fluid — Typical charecteristics
• * Highly viscous
• * Clear
• * Essentially acellular
• * Protein concentration approximately 45%
that of plasma
• * Glucose concentration similar to that in
plasma
• Concentrations of electrolytes and small
molecules are equivalent to those in plasma

9. • Hyaluronic acid is synthesized by fibroblast-like
synovial lining cells, and it appears in high
concentrations in synovial fluid at around 3 g/L,
compared with a plasma concentration of 30
μg/L.
• Lubricin, a glycoprotein that assists articular
lubrication, is another constituent of synovial
fluid that is generated by the lining cells
• Their function is to provide lubrication to the
articular surfaces

10. • In normal joints, intra-articular pressures are
slightly subatmospheric at rest (0 to -5 )
• During exercise, hydrostatic pressure in the
normal joint may decrease further
• Resting intra-articular pressures in rheumatoid
joints are around 20 mm Hg, whereas during
isometric exercise, they may increase to
greater than 100 mm Hg, well above capillary
perfusion pressure and, at times, above
arterial pressure

11. • Synovial fluid may be collected by syringe in a
procedure termed arthrocentesis, also known
as joint aspiration
• Categories of joint effusions — Results of
synovial fluid analysis can be used to
categorize the fluid as noninflammatory,
inflammatory, septic, or hemorrhagic based
upon the clinical and laboratory analysis

12. • COMPONENTS OF SYNOVIAL FLUID ANALYSIS
• Gross appearance — The volume, clarity, color,
and viscosity of joint fluid are noted.
• Clarity — Increased opacity of the fluid is
usually due to abnormally large numbers of
nucleated or red blood cells. However,
translucent or even opaque fluid may be the
result of acellular material. Examples include
lipids in fat necrosis, cholesterol crystals in
chylous effusions, or innumerable
monosodium urate crystals aspirated from
gouty tophi

13. • Color — Colorless, clear fluid is normal, while
increasing amounts of plasma and nucleated cells
contribute to the yellow or yellow-green
appearance of inflammatory or septic fluids.
Bright red, rusty, or chocolate brown fluids are
indicative of fresh or old blood
• Viscosity — As joint fluid is expelled from the
syringe and allowed to drop into a suitable
receptacle normal fluid will produce a long string-
like extension as it falls. Release of proteolytic
enzymes into inflamed synovial fluid typically
generally causes a decrease in viscosity. However,
frankly purulent (septic) effusions may also be
viscous

14. • Microscopic examination — The microscopic
examination of synovial fluid may be
performed on as little as one drop of
uncentrifuged fluid (wet mount), however,
examination of the sediment of a centrifuged
specimen may improve the sensitivity of the
microscopic examination for crystals

15. • Cell count — Normal synovial fluid is nearly
acellular. Inflammatory and septic synovial
fluids are characterized by increasing numbers
of leukocytes. Bacterial joint infections
typically are purulent with leukocyte counts
(most of which are neutrophils) of 50,000 to
150,000 cells/mm3

16. • Crystal search — Examination of synovial fluid for
monosodium urate (MSU) crystals and calcium
pyrophosphate dihydrate (CPPD) crystals is
facilitated by having a microscope with polarizing
filters and a quarter wave plate
• Other crystals — Crystals other than MSU and
CPPD may have a role in the pathogenesis of
some diseases. Examples include crystals of
cholesterol, hydroxyapatite, and basic calcium
phosphate.

17. • Gram stain — The synovial fluid Gram stain is an easily
performed test that can provide immediate, useful
information concerning the diagnosis and therapy
(Gram positive versus Gram negative coverage) of
septic arthritis
• Despite its utility, the sensitivity and specificity of
synovial fluid Gram stain is not known precisely. In
nongonococcal bacterial arthritis, the sensitivity of
Gram stain has been estimated to range from 50 to 70
percent . In gonococcal arthritis the sensitivity is much
lower, probably <10 percent .

18. • Routine bacterial culture — The synovial fluid
samples should be routinely sent for culture of
the common nongonococcal causes of
bacterial arthritis: staphylococci followed by
streptococci and Gram negative bacteria
• Antibiotics should generally not be given prior
to joint aspiration. If they have the likelihood
of recovering a pathogenic microorganism
from synovial fluid may be increased if the
fluid is first inoculated into a commercial
culture systems that contain antibiotic-binding
beads

19. • When should cultures be sent for unusual organisms?
— The history may reveal clues suggesting the
possibility of an unusual cause of septic arthritis:
•
• * A history of tuberculosis exposure
• * A history of trauma
• * Travel to or living in an area endemic with fungal
infections or Lyme disease
• * The presence of immune suppression
• * A monoarthritis that is refractory to conventional
therapy

23. bloody fluid with a thicker layer of lipid material separated after
centrifugation was aspirated from a patient with a tibial fracture into the joint
space

24. This is the colorless, clear synovial fluid from a patient with osteoarthritis
accompanied by a low synovial-fluid white cell count.

25. These fluid collections which serve as good samples of cloudy but translucent
inflammatory synovial fluid were taken from a patient with rheumatoid
arthritis (left) and gout (right) respectively

26. this fluid is a good example of a cloudy, pus-like fluid aspirated from a patient
with acute bacterial infectious arthritis

27. Monosodium urate crystal

28. • SUMMARY AND RECOMMENDATIONS
* Synovial fluid analysis may be diagnostic in
patients with bacterial joint infection and
crystal-induced arthritis. This analysis is
indicated in febrile patients with an acute flare
of already established arthritis and in other
situations in which the cause of a joint
effusion is uncertain or septic arthritis is
suspected

29. • * The volume of synovial fluid removed is noted along with
the clarity, color, and viscosity.
• * The most valuable components of laboratory analysis of
synovial fluid are: the white cell count, differential count,
cultures, Gram stain, and crystal search using polarized light
microscopy
• * Normal synovial fluid is viscous, clear, colorless and
nearly acellular. Abnormal synovial fluids are categorized
into those that are noninflammatory, inflammatory, septic,
and hemorrhagic as a means to reduce the number of
possible causes of effusions to consider in the differential
diagnosis. However, for each category there is significant
diagnostic overlap.
• * Gonococcal, Borrelial (Lyme disease), mycobacterial, or
fungal joint infections should be suspected when routine
bacterial cultures of synovial fluid do not yield a pathogenic
organism. Additional diagnostic tests are suggested when
these diseases are suspected.

30. • THANK YOU

31. References
• Kelley’s Textbook of Rheumatology,8th Edition
• UptoDate ,2011
• CURRENT Rheumatology Diagnosis &
Treatment,second edition