Synovial Fluid

1 CHAPTER11 Synovial FluidSynovial FluidKey TermsANTINUCLEAR ANTIBODY arthrocentesis BULGE TEST CRYSTAL-INDUCED ARTHRITIS GROUND PEPPERHYALURONATEMUCINOCHRONOTIC SHARDSRHEUMATOID ARTHRITIS (RA)RHEUMATOID FACTOR (RF)RICE BODIESROPE S TESTSEPTIC ARTHRITIS SYNOVIALSYSTEMIC LUPUS ERYTHEMATOSUS VISCOSITYL earning Objectives1. Define Describe the formation and function of Synovial Explain the collection and handling of Synovial Describe the appearance of normal and abnormal Synovial Correlate the appearance of Synovial Fluid with possible Interpret laboratory tests on Synovial Suggest further testing for Synovial Fluid , based on preliminary List the four classes or categories of joint Correlate Synovial Fluid analyses with their representative disease 11/18/09 6:04 PM Page 253 Aptara Inc254 Graff s Textbook of Routine Urinalysis and Body FluidsJoint Fluid is called synovialfluid because of its resem-blance to egg white.

2 It is a viscous, mucinous substancethat lubricates most joints. Analysis of Synovial Fluid isimportant in the diagnosis of joint disease. Aspiration ofjoint Fluid is indicated for any patient with a joint effusionor inflamed joints. Aspiration of asymptomatic joints isbeneficial for patients with gout and pseudogout as thesefluids may still contain of physical,chemical, and microscopic characteristics of Synovial fluidcomprise routine analysis. This chapter includes anoverview of the composition and function of Synovial Fluid ,and laboratory procedures and their AND COMPOSITION All human joints, except those that are weight bearing, arelined with a tissue called synovium. Synovium producessynovia, also called Synovial Fluid capsule cush-ions diarthrotic joints allowing the bones to freely articu-late.

3 A dense connective tissue layer of collagen surroundsthe Synovial 11-1 illustrates an articulatedjoint. Figure 11-2 shows the Synovial lining of the Fluid is an ultrafiltrate or dialysate of plasma andcontains levels of glucose and uric acid that are equivalent toplasma. Synovial Fluid protein, however, is at a lower level(about one third) than that of plasma. Plasma constituentsthat enter joint Fluid must cross a double-barrier , the endothelial lining of the capillaries is traversed fol-lowed by movement through a matrix that surrounds syn-ovial cells. This ultrafiltrate is combined with a mucopolysac-charide (hyaluronate) synthesized by the COLLECTIONA fter finding positive results with a bulge test (Fig. 11-3),the physician will perform an arthrocentesisand aspiratethe effected joint.

4 An appropriate gauge needle is attachedto a syringe and the entry site is cleansed. A two-stepprocess is employed for arthrocentesis in which the firstpuncture is made through the skin followed by a secondthrust into the Synovial capsule. Figure 11-4 illustratesneedle placement in arthrocentesis of elbow and knee Fluid is aspirated and the needle withdrawn fromthe joint, the needle is removed and an end cap placed onthe tip of the syringe. The syringe is properly labeled andsent to the laboratory for laboratoriesBoneLigamentArticulatingbone Synovial (joint)cavity (contains Synovial Fluid )ArticularcartilageArticulating bonePeriosteumArticularcapsule: Fibrous capsule Synovial membrane LigamentFigure joint. (From Oatis CA. Kinesiology.)

5 TheMechanics and Pathomechanics of Human Movement. Baltimore:Lippincott Williams & Wilkins, 2003.)Figure membrane from a normal knee joint showsjoint space, Synovial membrane composed of Synovial cells embedded ina loose connective tissue stroma overlying dense collagen (hematoxylinand eosin). (From McClatchey KD. Clinical Laboratory Medicine. 2nd : Lippincott Williams & Wilkins, 2002.)Lateral thighFigure test of joint for the detection of Synovial effusion. 11/18/09 6:04 PM Page 254 Aptara Increquire that Synovial Fluid specimens be placed in specimencontainers appropriate for the tests ordered. A heparinizedtube is preferable to ethylenediaminetetraacetic acid (EDTA)or other anticoagulants for cells counts; sterile containersfor microbiology testing; and plain tubes are normally usedfor chemistry and immunology testing of Synovial Fluid specimens should be handled like STAT spec-imens and delivered immediately to the laboratory for test-ing to avoid alteration of chemical constituents, cell lysis,and problems in microorganism detection and identifica-tion.

6 If a glucose test is to be performed, the patient shouldbe fasting for at least 6 hours prior to collection of jointfluid. A 6-hour fast is necessary to establish an equilibriumbetween plasma and joint glucose 4 LABORATORY TESTING Volume. The amount of Fluid contained in joints isusually small. The knee joint normally contains up to4 mL of Fluid . The volume of the aspirate is usuallyrecorded at bedside, but some laboratories mayinclude volume in their reports as ,3 Color and clarity. Normal Synovial Fluid is colorless andclear. Other appearances may indicate various diseasestates. Yellow/clear Synovial fluids are typical in nonin-flammatory effusions, whereas yellow/cloudy fluidsusually involve an inflammatory processes. A white/cloudy Synovial Fluid may contain crystals; and syn-ovial Fluid that is red, brown, or xanthochromic indi-cates hemorrhage into the joint.

7 In addition, synovialfluid may contain various types of inclusions. Free-floating aggregates of tissue appear as rice bodies. Ricebodies are seen in rheumatoid arthritis (RA)and resultfrom degenerated synovium enriched with shardsare debris from metal and plasticjoint prosthesis. These shards look like ground 11-5 compares normal and blood synovialfluids, whereas Figure 11-6 (page 260) demonstratesthe appearance of Synovial Fluid inclusions. Viscosity. Synovial Fluid is very viscous due to its highconcentration of polymerized hyaluronate. A stringtest can be used to evaluate the level of Synovial fluidviscosity. After removing the needle or cap from thesyringe, Synovial Fluid is expressed into a test tube onedrop at a time. Normal Synovial Fluid will form a string approximately 5 cm long before breaking.

8 Inaddition, the Fluid may cling to the side of the testtube rather than running down to the bottom. Syn-ovial fluids with poor viscosity will form shorter stingsChapter 11 Synovial Fluid255 Lateral viewAFigure of needle in arthrocentesis of (A) elbow and(B) knee joints. BFigure Fluid . 11/18/09 6:04 PM Page 255 Aptara Inc256 Graff s Textbook of Routine Urinalysis and Body Fluids( 3 cm) or run out of the syringe and down the side ofthe test tube like ,4 Low viscosity of synovialindicates the presence of an inflammatory 11-7 illustrates the performance of the stringtest for Synovial Fluid viscosity. Clotting. Clotting of Synovial Fluid can result when fib-rinogen is present. Fibrinogen may have entered intothe Synovial capsule during damage to the synovialmembrane or as a result of a traumatic inspecimens interfere with performance of cell part of the specimen into a tube contain-ing heparin may help avoid clotting of Synovial Fluid .

9 Mucin clot. The mucinclot test, also known as Rope s test,is an estimation of the integrity of the hyaluronicacid protein complex (mucin). Normal Synovial fluidforms a tight ropy clot upon the addition of acetic procedure for mucin clot varies among laboratoriesas evidenced by differing Fluid to acid ratios appearing invarious texts. Clinical laboratory professionals shoulduse the procedure adopted by their laboratories. Table11-1 demonstrates this variability. In all cases, the inter-pretation of clot formation is the same. A good mucinclot indicates good integrity of the hyaluronate. A poormucin clot, one that breaks up easily, is associated withdestruction or dilution of Figure 11-8illustrates the tight clot of normal Synovial EXAMINATION Protein. Synovial Fluid contains all proteins found inplasma, except various high molecular weight pro-teins.

10 These high molecular-weight proteins includefibrinogen, beta 2 macroglobulin, and alpha 2 macro-globulin, and can be absent or present in very lowamounts. Most commonly used serum protein proce-dures can be used to measure Synovial Fluid normal range for Synovial Fluid protein is 1 3 Synovial Fluid protein levels are seen inankylosing spondylitis, arthritis, arthropathies thatFigure Fluid inclusions. A. Ground pepper ochronoticshards. B. Rice bodies fibrin-enriched synovium test showing normal Synovial Fluid viscosity. Table 11-1 Mucin Clot Procedure According to Referenced TextsVOLUME OF VOLUME AND STRENGTH AUTHORSYNOVIAL FLUIDOF ACETIC ACIDB runzel3 One partFour parts, 2%Ross and Neely4 One partFour parts, 2%McBride2 Two partsOne part, 3%Strasinger5 Not 11/18/09 6:04 PM Page 256 Aptara Incaccompany Crohn disease, gout, psoriasis, Reiter syn-drome, and ulcerative Glucose.