Synovial Fluid Flashcards
Synovial Fluid
Synovial = syn (like) + ovia (egg)
Mucinous substance that lubricates most joints
Used in the analysis and diagnosis of joint disease
Synovial Fluid - mucinous substance that lubricates most joints
Articulated Joint Anatom
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).
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
Specimen Collection
Needle insertion
Placement of needle in arthrocentesis of (A) elbow and
(B) knee joints.
Testing: Macroscopic
Volume Color and Clarity Inclusions Viscosity Clotting Mucin Clot
Testing: Macroscopic: Volume
Normal up to 4 mL of fluid
Result usually recorded at bedside
Some laboratories may include volume in reports
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
Macroscopic Analysis: Inclusions
Ochronotic shards = A
debris from joint prosthesis
look like ground pepper
Rice bodies = B rheumatoid arthritis (RA) synovium enriched with fibrin
Macroscopic Analysis: Viscosity
Evaluated using “String test”
Normal = 5cm long before breaking
Low viscosity indicates inflammation
String test showing normal synovial fluid viscosity.
Macroscopic Analysis: Clotting
Clotting of synovial fluid = fibrinogen
Damaged synovial membrane
Traumatic tap
Clots interfere with performance of cell counts
Macroscopic Analysis: Mucin Clot
Estimation of hyaluronic acid–protein complex integrity “Rope’s test” Add acetic acid Good = tight ropey mass = normal
Poor = beaks easily
haluronate destruction
haluronate dilution
Testing: Chemical
Protein Glucose Uric Acid Lactic Acid Lactate Dehydrogenase Rheumatoid Factor
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 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
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
Chemical Analysis: Uric Acid
Normal - 6 to 8 mg/dL
Increased – gout
May form crystals
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
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.
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.
Microscopic Analysis: Cell Counts
Perform within 1 hour of specimen collection Usually counted manually Normal values: RBCs = none WBCs = 0 – 150/cumm
Microscopic Analysis: Differential
Cytocentrifuge prepared smears Normal values: Neutrophils 7% Lymphocytes 24% Monocytes (Histocytes) 48% Macrophages 10% Synovial lining cells 4%
Normal cellular elements found in synovial fluid
A = neutrophil B = lymphocyte C = monocytes (histiocytes) D = lining cells
Elevated neutrophils
Septic arthritis
Later stages of RA
phagocytes
Synovial fluid with acute inflammation demonstrating
neutrophilic pleocytosis (Wright–Giemsa).
Elevated Monocytes
Serum sickness associated arthritis
Viral infections
Crystal-induced arthritis
