Chapter 11:
Synovial Fluid
Graff’s Textbook of Urinalysis and Body Fluids,
Second Edition
Mundt, L. & Shanahan K.
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Chapter Outline
• Physiology and Composition of Synovial Fluid
• Specimen Collection
• Laboratory Testing
– Macroscopic Evaluation
– Chemical Examination
– Microscopic Examination
• Classification of Joint Disorders
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Synovial Fluid
• Synovial = syn (like) + ovia (egg)
• Mucinous substance that lubricates most joints
• Used in the analysis and diagnosis of joint disease
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Synovial Fluid
• Joint Anatomy
Articulated joint.
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Synovial Fluid
• Synovial Membrane
Synovial membrane from a normal knee joint shows
joint space, synovial membrane composed of synovial
cells embedded in a loose connective tissue stroma
overlying dense collagen (hematoxylin and eosin).
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Synovial Fluid: Physiology and Composition
• Clear viscous ultra filtrate of plasma
• Glucose and uric acid equivalent to plasma
• Protein lower than plasma
• Hyaluronate protein complex containing mucin
– Moistens and lubricates joints
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Synovial Fluid: Specimen Collection
• Bulge test
Bulge test of joint for the detection of synovial effusion.
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Synovial Fluid: Specimen Collection
(cont.)
• Needle insertion
Placement of needle in arthrocentesis of (A) elbow and
(B) knee joints.
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Laboratory Testing: Macroscopic
• Volume
• Color and Clarity
• Inclusions
• Viscosity
• Clotting
• Mucin Clot
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Laboratory Testing: Macroscopic
• Volume
– Normal up to 4 mL of fluid
– Result usually recorded at bedside
– Some laboratories may include volume in reports
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Macroscopic Analysis: Color and Clarity
• Colorless and clear
– normal
• Red, brown, or xanthochromic
– hemorrhage into the joint
• Yellow/clear
– noninflammatory effusions
• Yellow/cloudy
– inflammation
• White/cloudy
– crystals
Synovial Fluid
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Macroscopic Analysis: Inclusions
• Rice bodies
– rheumatoid arthritis (RA)
– synovium enriched with fibrin
–
• Ochronotic shards
– debris from joint prosthesis
– look like ground pepper
Synovial Fluid Inclusions
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Macroscopic Analysis: Viscosity
• Evaluated using “String test”
• Normal = 5cm long before breaking
• Low viscosity indicates inflammation
String test showing normal
synovial fluid viscosity.
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Macroscopic Analysis: Clotting
• Clotting of synovial fluid = fibrinogen
• Damaged synovial membrane
• Traumatic tap
• Clots interfere with performance of cell counts
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Macroscopic Analysis: Mucin Clot
• Estimation of hyaluronic acid–protein complex integrity
• Evaluated using “Rope’s test”
• Good = tight ropey mass
– normal
• Poor = beaks easily
– haluronate destruction
– haluronate dilution
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Macroscopic Analysis: Mucin Clot (cont.)
Mucin clot test of normal
synovial fluid.
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Laboratory Testing: Chemical
• Protein
• Glucose
• Uric Acid
• Lactic Acid
• Lactate Dehydrogenase
• Rheumatoid Factor
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Chemical Analysis: Protein
• All proteins found in plasma
• Exception: various high–molecular weight proteins which
may be present in very small amount
– fibrinogen
– beta 2 macroglobulin
– alpha 2 macroglobulin
• Use common serum protein procedures
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Chemical Analysis: Protein (cont.)
• Normal range 1-3 g/dl
• Increased protein
– ankylosing spondylitis
– arthritis
– Crohn disease
– Gout
– Psoriasis
– Reiter syndrome
– ulcerative colitis.
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Chemical Analysis: Glucose
• Compare to serum glucose levels
• Normal synovial glucose is no lower than 10mg/dl less
than serum glucose levels.
• Decreased – joint disorders
• Greater than 20mg/dl decrease may indicate infection
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Chemical Analysis: Uric Acid
• Normal - 6 to 8 mg/dL
• Increased – gout
• May form crystals
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Chemical Analysis: Lactic Acid
• Rarely measured in synovial fluid
• Can be helpful in diagnosing septic arthritis.
• Normal = less than 25 mg/dL
• Septic arthritis can show levels up to 1000 mg/dL
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Laboratory Testing: Lactate Dehydrogenase
• May be elevated in synovial fluid, while serum levels
remain normal.
• Increased in
– Rheumatoid arthritis (RA)
– infectious arthritis,
– gout.
• Neutrophils increased during the acute phase of these
disorders contribute to this increased LD.
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Laboratory Testing: Rheumatoid Factor
• RF is an antibody to immunoglobulins.
• Present in rheumatoid arthritis:
– Serum – most cases
– Synovial fluid - 50%
– Rarely elevated only in synovial fluid and not serum
• False positives in other chronic inflammatory diseases.
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Laboratory Testing: Microscopic
• Cell Counts
• Differential
• Crystals
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Microscopic Analysis: Cell Counts
• Perform within 1 hour of specimen collection
• Usually counted manually
• Normal values:
– RBCs = none
– WBCs = 0 – 150/cumm
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Microscopic Analysis: Differential
• Cytocentrifuge prepared smears
• Normal values:
– Neutrophils
7%
– Lymphocytes
24%
– Monocytes (Histocytes) 48%
– Macrophages
10%
– Synovial lining cells
4%
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Microscopic Analysis: Differential (cont.)
Normal cellular elements found in synovial fluid
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Microscopic Analysis: Differential (cont.)
• Elevated neutrophils:
– Septic arthritis
– Later stages of RA
• ragocytes
Synovial fluid with acute
inflammation demonstrating
neutrophilic pleocytosis
(Wright–Giemsa).
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Microscopic Analysis: Differential (cont.)
• Elevated Monocytes
– Serum sickness associated arthritis
– Viral infections
– Crystal-induced arthritis
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Microscopic Analysis: Differential (cont.)
• Elevated lymphocytes:
–
Early stages of RA
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Microscopic Analysis: Differential (cont.)
• LE cells
• Tart cells
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Microscopic Analysis: Differential (cont.)
• Reiter cells
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Microscopic Analysis: Differential (cont.)
• Differential-Lipophage
Lipid-laden macrophage
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Microscopic Analysis: Crystals-Uric Acid
Synovial fluid with acute inflammation
and monosodium urate crystals.
(Wright–Giemsa stain and polarized
light).
Synovial fluid with acute inflammation
and monosodium urate crystals. The
needle-shaped crystals demonstrate
negative birefringence, because they are
yellow when aligned with the ompensator
filter and blue when perpendicular to the
filter (Wright–Giemsa stain and
polarized/compensated light).
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Microscopic Analysis: Crystals-other
Synovial fluid with acute inflammation
and calcium pyrophosphate dihydrate
crystals (Wright–Giemsa stain and
polarized light).
Synovial fluid with acute inflammation and
calcium pyrophosphate dihydrate crystals.
The rhomboidal intracellular crystal (center)
demonstrates positive birefringence,
because it is blue when aligned with the
compensator filter (Wright–Giemsa stain
and polarized/compensated light).
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Microscopic Analysis: Crystals-other
• Corticosteroid crystals :
– intra-articular injections
• Cholesterol crystals :
– chronic effusionsmfrom patients with
osteoarthritis or RA
• Apatite crystals :
– calcific periarthritis
– osteoarthritis
– inflammatory arthritis
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Laboratory Testing: Microbiology
• Infectious organisms
– Bacteria
– Fungi
– Mycobacteria
– Viruses
• Route of entry
– Bloodstream
– Penetrating wounds
– Osteomyelitis rupture
– Arthroscopy
– intra-articular steroidm injections
– prosthetic joint surgery
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Laboratory Testing: Microbiology (cont.)
• Staining
– Smears prepared by centrifugation or
cytocentrifugation
– Saline dilution reduces clustering of cells
– Gram’s stain most common
Positive in only 50% of cases
• Culture
– Set up with positive or negative stain results
– Aerobic
– anaerobic
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Classification of Joint Disorders
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Review of Key Points
• Synovial fluid analysis
– Is a well-established procedure for evaluation of joint
disease.
– Determines the presence of arthritis
– Assists in the classification of joint disorders
– Helps guides appropriate treatments
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