Synovial Fluid

Question 1

What is synovial fluid?

Answer 1

Joint fluid formed by synovial cells lining the joint and by ultrafiltration of plasma.

Question 2

What does the synovial membrane do?

Answer 2

Acts like the blood-brain barrier; higher molecular weight compounds can’t cross.

Question 3

What is hyaluronate?

Answer 3

A mucoprotein containing hyaluronic acid found only in synovial fluid, providing lubrication, nutrients, and viscosity.

Question 4

Why examine joint fluid?

Answer 4

To assess swelling of the joint.

Question 5

What are normal joint fluid levels?

Answer 5

0.1-2 mL of fluid; amount taken depends on swelling.

Question 6

What is arthrocentesis?

Answer 6

The procedure of removing joint fluid.

Question 7

What should normal joint fluid look like?

Answer 7

Clear to pale yellow, viscous, should not be clotted, and contain no blood.

Question 8

How should collected joint fluid be processed?

Answer 8

It should go in 3 separate tubes: EDTA tube for cell counts, Heparin/non-additive tube for chemistry/serology, and a non-additive tube for microbiology.

Question 9

What are the parameters of non-inflammatory joint fluid?

Answer 9

Clear fluid, normal viscosity, WBC <1,000/mL, glucose equal to serum glucose, neutrophils <30%.

Question 10

What are the parameters of inflammatory joint fluid?

Answer 10

Less viscous, slightly cloudy appearance, high WBC count, more than 50% neutrophils, decreased glucose compared to serum glucose, presence of crystals.

Question 11

What are the parameters of septic joint fluid?

Answer 11

Cloudy, yellowish/greenish, WBC count >100,000/mL, 75-80% neutrophils, decreased glucose.

Question 12

What are the parameters of hemorrhagic joint fluid?

Answer 12

Red color, lower viscosity, more RBCs than WBCs, glucose levels normal to decreased.

Question 13

What is the String Test?

Answer 13

A screening test where fluid should form a string 4-6 cm long before dropping from the pipette tip.

Question 14

What is the Mucin Clot Test?

Answer 14

A test where hyaluronate and acetic acid form a clot; qualitative and quantitative assessments can be made.

use 2-5% acetic acid

Question 15

What should be added before doing a cell count?

Answer 15

Hyaluronidase, an enzyme that breaks down hyaluronate.

Question 16

What should you not add to destroy RBCs?

Answer 16

Glacial acetic acid, as it will cause clotting; hypotonic saline should be used instead.

Question 17

What is an LE cell?

Answer 17

A macrophage that ingests neutrophils, present in 90% of people with active lupus.

LE= lupus erythematosus

Question 18

What is the first crystal to look for in synovial fluid?

Answer 18

Monosodium urate (uric acid) crystals, seen in gout; characterized by needle-like projections and negative birefringence.

Question 19

What are calcium pyrophosphate crystals associated with?

Answer 19

Increased levels of calcium deposits; associated with pseudo gout and degenerative arthritis.

affects larger joints
rhombus shapes

POSITIVE bifringence

Question 20

What do corticosteroid crystals indicate?

Answer 20

Presence in patients on steroids, such as those with lupus or rheumatoid arthritis.

POSITIVE AND NEGATIVE BIREFRINGENCE

Question 21

What do cholesterol crystals look like?

Answer 21

Rectangles with notched corners, seen in lipidemia and chronic RA; does not stain.

Question 22

What should glucose levels in synovial fluid be?

Answer 22

They should be similar to serum values, not differing more than 10%.

Question 23

What is the Rheumatoid Factor?

Answer 23

An IgM produced against the altered Fc portion of IgG, found in 90% of active rheumatoid arthritis cases.

found in rheumatoid arthritis

Question 24

What complement levels should be looked for in synovial fluid?

Answer 24

C3 and C4 levels; total complement levels decrease when active.

levels decrease because being spilt and utilized

Question 25

What should be looked for in microbiology testing of synovial fluid?

Answer 25

Septic arthritis causes, such as Neisseria Gonorrhea, MRSA, and Borrelia antibodies.

Question 26

What are synovial lining cells?

Answer 26

Cells seen in synovial fluid that are larger than lymphocytes.

Question 27

hyaluronate purpose

Answer 27

lubrication, nutrients, and viscosity

Question 28

how does synovial fluid become hemorrhagic?

Answer 28

bleeding in joints due to malignancy, sickle cell anemia, traumatic injury, coagulation deficiencies

Question 29

what does hematology do for synovial fluid?

Answer 29

look macroscopically
look at viscosity
cell count

Question 30

for the mucin clot test what is the qualitative part

Answer 30

joint fluid and add a drop or 2 of acetic acid and shake for 5-10 sec

let it sit for it to clot
normal= solid clot
less = half a clot
severely decreased= no clot

Question 31

why can’t you add glacial acetic acid to destroy RBCs

Answer 31

it will clot because acetic acid

ADD: hypotonic saline

Question 32

what are ID crystals for

Answer 32

help identify different disease states

look in brightfield microscope and confirm in a polarizing microscope

ID needs to be done within a few hours within collection or will break down

Question 33

what crystal is put under polarizing microscope and see maltese cross formation

Answer 33

cholesterol crystals

Question 34

as complement levels go back to normal this indicates

Answer 34

inflammatory conditions are in check

Question 35

what else is looked for in the micro section for synovial fluid

Answer 35

antibodies to Borrelia
-agent of Lyme disease
-sign of this is joint pain