Synovial fluid

Synovial joint

• is the most common type of joint in the body.

• It is also called as diarthroses or movable joints.

• It allows free movement of the knees, hips, and shoulders.

Joint Capsule

Fibrous structure that encloses the joint.

Synovial Membrane

• A specialized membrane which lines the joint capsule.

• It contains synoviocytes.

Articular Cartilage

Smooth protective tissue lining of the bone ends.

Synovial Fluid

Viscous fluid filling the joint cavity

Type A cells

• are macrophage-like cells (phagocytosis).

• Seen on the outer or superficial layer of the synovial membrane.

Type B cells

• are fibroblast-like cells that produce hyaluronic acid, fibronectin, and collagen.

• They are found on the deeper layer of the membrane.

• They have prominent endoplasmic reticulum.

Functions of syn

Hyaluronic acid

Responsible for viscosity of synovial fluid.

1. Infections 

2. Inflammations

3. Trauma on the Side

4. Physical Stress

5. Advanced Age

Other types of disease processes that can cause the lesser viscosity of the synovial fluid:

Arthrocentesis

• is the needle aspiration of synovial fluid from a joint.

TRUE

TRUE OR FALSE: Synovial fluid is essentially an ultrafiltrate of plasma.

TRUE

TRUE OR FALSE: Fibrinogen is normally seen in plasma but not normally seen in synovial fluid.

Heparin

is the anticoagulant of choice in arthrosynthesis.

Tube 1 (Red Stopper)

• In processing this tube, it must be centrifuged to remove the cellular components because it is not used for any cellular visualization.

• used for chemical and immunologic studies.

Tube 2 (Lavender or Green Stopper)

The purpose of this tube is that it will be used for cell count, differential count, and crystal identification.

Tube 3 (Yellow or Green Stopper)

is used for microbiological studies

colorless to pale yellow

Normal color of synovial fluid

Color of synovial fluid if there are effusions

Clarity

is determined by the components found inside the fluid, such as the concentration of WBCs, RBCs, synovial sites, crystals, and other debris.

4-6 cm

Normal string measurement synovial fluid is?

Mucin clot or Rope’s test

Although rarely performed in laboratories today, this test can confirm whether an unlabeled fluid is synovial fluid, as synovial fluid reacts with acetic acid.

1. Clot must be solid

2. The surrounding fluid must be clear.

Two observations in mucin clot

Total WBC count

is the most frequently performed count on synovial fluid.

If the fluid is very viscous, pretreatment is required by adding one drop of

A condition wherein the WBC count exceed 100,000 cells/µL

• Performed on cytocentrifuged or thin smear slides.

• Stain usually used is Wright-Giemsa stain.

• Fluids are incubated with hyaluronidase to reduce viscosity.

• Normally seen are monocytes, macrophages, and synovial tissue cells.

septic conditions

Neutrophils are increased in?

non-septic inflammation

Lymphocytes are increased in?

Eosinophils

If more than 2% in differential count, it indicates a parasitic infection or rheumatoid arthritis.

Lupus erythematous cells

A neutrophil with a phagocytized nucleus or homogenous nucleus.

Reiter cells

• Also known as Neutrophages.

• These are macrophages with ingested neutrophils.

Rheumatoid arthritis cells

• Also known as Ragocytes.

• These are neutrophils containing small dark cytoplasmic granules that contains precipitated rheumatoid factor.

lipid droplets

• are present after crush injuries.

• Distinct in differential slide because they are refractive

Hemosiderin granules

• are pigmented villonodular synovitis.

• Brown to black pigments.

• amounts indicate that the patient may have tuberculosis.

• Septic and rheumatoid arthritis

Monosodium Urate (MSU) Crystals

• Associated with gout

• Needle-shaped.

• Negative birefringence.

• Also seen in increased purine metabolism.

• Decreased renal excretion of uric acid.

Calcium pyrophosphate dihydrate crystals

• The main disease association is pseudogout.

• Rhomboid-shape.

• Positive birefringence.

Hydroxyapatite Crystals

• Also called basic calcium phosphate crystals.

• Usually associated with calcified cartilage degeneration.

Cholesterol Crystals

Usually seen in chronic inflammation (rheumatoid arthritis).

Corticosteroids Crystals

are seen usually after intra-articular injection.

Calcium Oxalate Crystals

are usually seen on patients who are undergoing renal dialysis.

Birefringence

is the ability of a crystal to refract light into two different directions.

Glucose

• Most frequently requested.

• A marked decrease in synovial fluid compared to plasma indicates an inflammatory or septic

Inflammation

Typically 0-40 mg/dL lower than plasma glucose levels.

Infectious or Septic Processes

Synovial fluid glucose levels are typically 20-100 mg/dL lower than plasma glucose.

Crystal-Induced Joint Diseases

Synovial fluid glucose levels are typically 0-80 mg/dL lower than plasma glucose.

Total protein

• Little diagnostic significance because most of the diseases except non-inflammatory synovial diffusion

• May increase in inflammatory or hemorrhagic disorders

<3.0g/dL

Normal value of total protein in synovial fluid

uric acid

• Elevated in gout.

• Only detect if there is doubt on whether the diagnosis is gout or there is no visualization of Monosodium Urate (MSU) crystals.

• May be used to confirm when the presence of Monosodium Urate (MSU) crystals cannot be appreciated in the fluid

Lactate

Elevated levels strongly indicate bacterial arthritis (>9 mmol/L).

Polymerase Chain Reaction (PCR) 

Detects Borrelia (Lyme disease) and Mycobacterium tuberculosis which are difficult to culture.

Serological testing

• used together with synovial fluid analysis to confirm autoimmune diseases.

• Tests use patient serum, which serves as blood-based confirmatory measures.

Group I: Noninflammatory

Degenerative joint disorders and osteoarthritis.

Group II: Inflammatory

• Immunologic disorders, rheumatoid arthritis, systemic lupus erythematosus, scleroderma, polymyositis, ankylosing spondylitis, rheumatic fever, and Lyme arthritis.

• Crystal-induced gout and pseudogout.

• Traumatic injury, tumors, hemophilia, and other coagulation disorders. Anticoagulant overdose