Synovial Fluid and Arthrocentesis

Latin word for egg

Diarthroses (movable joints)

Hyaluronic acid

Type B synoviocytes (Type A = phagocytosis)

Affects production of hyaluronate and its ability to polymerize, thus decreasing synovial fluid viscosity

1. Lubricates joints, 2. Reduce friction between bones, 3. Provides nutrients to the articular cartilage, 4. Lessen shock of joint compression occurring during activities such as walking and jogging

Arthrocentesis

Normal synovial fluid does not clot (diseased joints may clot)

Normal: 3.5 mL; Inflammation: >25 mL

Plain red top tube (no anticoagulant)

Sodium fluoride (gray)

Sodium heparin or Liquid EDTA

Powdered anticoagulants and lithium heparin

Do NOT refrigerate samples - this can produce additional crystals!

Sterile anticoagulant tube (heparin or SPS)

Colorless to pale yellow & clear

Inflammation

Bacterial infection

Traumatic tap; hemorrhagic arthritis

WBCs, synovial cell debris or fibrin

Presence of crystals

4-6 cm long

0.3 to 0.4 g/dL

2-5% acetic acid

Solid or compact clot, clear solution

Soft clot

Friable clot, cloudy solution

No clot

1. NSS with methylene blue, 2. Hypotonic saline (0.3%), 3. Saline with saponin

Acetic acid

Add a pinch of hyaluronidase to 0.5 mL fluid (or 1 drop of 0.05% hyaluronidase in phosphate buffer per mL of fluid) and incubate at 37°C for 5 minutes

<2,000/µL (Turgeon = ABSENT)

<200/µL

65%

<25%

<15%

Bacterial sepsis; crystal-induced inflammation

Nonseptic inflammation

Large mononuclear leukocyte, may be vacuolated; normal, viral infections

Neutrophil containing ingested "round body"; Lupus erythematosus

Vacuolated macrophage w/ ingested neutrophils; Reactive arthritis (a.k.a. Reiter syndrome)

Neutrophil with dark cytoplasmic granules containing precipitated rheumatoid factor; Rheumatoid arthritis, immunologic inflammation

Macroscopically resemble polished rice, microscopically show collagen & fibrin; Tuberculosis, septic and rheumatoid arthritis

Debris from metal & plastic joint prosthesis, "ground pepper" appearance; Ochronotic arthropathy, alkaptonuria, ochronosis

Large, multinucleated cells; Osteoarthritis

Similar to macrophage, but may be multinucleated, resembling a mesothelial cell; Normal, disruption from arthrocentesis

Refractile intracellular & extracellular globules, stain with Sudan dyes; Traumatic injury, chronic inflammation

Inclusions within clusters of synovial cells; Pigmented villonodular synovitis

Normal synovial fluid should NOT contain any crystal!

1. Metabolic disorders, 2. Decreased renal excretion that produce increased blood levels of crystallizing chemicals, 3. Degeneration of cartilage and bones, 4. Injection of medications (corticosteroid)

Needles; Negative birefringence; Gout

Rhombic square, rods; Positive birefringence; Pseudogout

Notched, rhombic plates; Negative birefringence; Extracellular

Flat, variable-shaped plates; Positive and Negative birefringence; Injections

Envelopes; Negative birefringence; Renal dialysis

Small particles (requires electron microscopy); No birefringence; Osteoarthritis (OA)

Detects for the presence or absence of birefringence (BR)

Confirms the type of birefringence (positive or negative BR) using a red compensator placed between crystal & analyzer

Molecules run parallel to long axis; slow light velocity unimpeded; produces YELLOW color = Negative birefringence

Molecules run perpendicular to long axis; slow light velocity retarded; produces BLUE color = Positive birefringence

Color is reversed

Glucose; tested within 1 hr in conjunction with blood glucose (after 8 hrs fasting)

<10 mg/dL

99 mg/dL - 10 mg/dL = 89 mg/dL

<25 mg/dL (increased in infection)

<3 g/dL (~1/3 of plasma protein); increased in inflammatory and hemorrhagic disorders

Same as blood (increased in gout)

ACP, ALP, GGT, ADA, MURA, CD, LDH, AST

S. aureus

Streptococcus, Haemophilus

N. gonorrhoeae

Autoantibody detection (SLE, RA); Detection of antibodies to Borrelia burgdorferi (Lyme disease)

Degenerative joint disorders (OA); Clear, yellow fluid; Good viscosity; WBC <1,000/µL; Neutrophils <30%

Immunologic disorders (RA, SLE); Cloudy, yellow fluid; Poor viscosity; WBC 2,000-75,000/µL; Neutrophils >50%; (+) Autoantibodies

Gout, Pseudogout; Cloudy/milky fluid; Low viscosity; WBC up to 100,000/µL; Neutrophils <70%; (+) Crystals

Microbial infection; Cloudy, yellow-green fluid; Variable viscosity; WBC 50,000-100,000/µL; Neutrophils >75%; (+) Culture and Gram stain

Traumatic injury, coagulation deficiencies; Cloudy, red fluid; Low viscosity; WBC & Neutrophils equal to blood; (+) RBCs