Synovial fluid - wikipedia Synovial fluid `` Synovia '' redirects here. For the plural of synovium, see synovial membrane. Synovial fluid A typical joint Details Identifiers Latin synovia MeSH D013582 TA A03. 0.00. 031 FMA 12277 Anatomical terminology ( edit on Wikidata ) Synovial fluid, also called synovia, is a viscous, non-Newtonian fluid found in the cavities of synovial joints. With its egg white -- like consistency, the principal role of synovial fluid is to reduce friction between the articular cartilage of synovial joints during movement. Synovial fluid is a small component of the transcellular fluid component of extracellular fluid. Contents 1 Structure 1.1 Composition 2 Clinical significance 2.1 Collection 2.2 Classification 2.3 Pathology 3 Analysis 3.1 Chemistry 3.2 Microscopy 3.3 Cracking joints 4 Etymology and pronunciation 5 References 6 Further reading 7 External links Structure The inner membrane of synovial joints is called the synovial membrane and secretes synovial fluid into the joint cavity. Synovial fluid is an ultrafiltrate from plasma, and contains proteins derived from the blood plasma and proteins that are produced by cells within the joint tissues. The fluid contains hyaluronan secreted by fibroblast - like cells in the synovial membrane, lubricin ( proteoglycan 4 ; PRG4 ) secreted by the surface chondrocytes of the articular cartilage and interstitial fluid filtered from the blood plasma. This fluid forms a thin layer ( roughly 50 μm ) at the surface of cartilage and also seeps into microcavities and irregularities in the articular cartilage surface, filling all empty space. The fluid in articular cartilage effectively serves as a synovial fluid reserve. During movement, the synovial fluid held in the cartilage is squeezed out mechanically to maintain a layer of fluid on the cartilage surface ( so - called weeping lubrication ). The functions of the synovial fluid include : reduction of friction -- synovial fluid lubricates the articulating joints shock absorption -- as a dilatant fluid, that possesses rheopectic properties, becoming more viscous under applied pressure ; the synovial fluid in diarthrotic joints becomes thick the moment shear is applied in order to protect the joint and subsequently, thins to normal viscosity instantaneously to resume its lubricating function between shocks. nutrient and waste transportation -- the fluid supplies oxygen and nutrients and removes carbon dioxide and metabolic wastes from the chondrocytes within the surrounding cartilage molecular sieving - pressure within the joint forces hyaluronan in the fluid against the synovial membrane forming a barrier against cells migrating into, or fluid migrating out of, the joint space. This function is dependent on the molecular weight of the hyaluronan. Composition Synovial tissue is sterile and composed of vascularized connective tissue that lacks a basement membrane. Two cell types ( type A and type B) are present : Type A is derived from blood monocytes, and it removes the wear - and - tear debris from the synovial fluid. Type B produces hyaluronan. Synovial fluid is made of hyaluronic acid and lubricin, proteinases, and collagenases. Synovial fluid exhibits non-Newtonian flow characteristics ; the viscosity coefficient is not a constant and the fluid is not linearly viscous. Synovial fluid has rheopexy characteristics ; viscosity increases and the fluid thickens over a period of continued stress. Normal synovial fluid contains 3 -- 4 mg / ml hyaluronan ( hyaluronic acid ), a polymer of disaccharides composed of D - glucuronic acid and D-N - acetyl glucosamine joined by alternating beta - 1, 4 and beta - 1, 3 glycosidic bonds. Hyaluronan is synthesized by the synovial membrane and secreted into the joint cavity to increase the viscosity and elasticity of articular cartilages and to lubricate the surfaces between synovium and cartilage. Synovial fluid contains lubricin ( also known as PRG4 ) as a second lubricating component, secreted by synovial fibroblasts. Chiefly, it is responsible for so - called boundary - layer lubrication, which reduces friction between opposing surfaces of cartilage. There also is some evidence that it helps regulate synovial cell growth. It also contains phagocytic cells that remove microbes and the debris that results from normal wear and tear in the joint. Clinical significance Collection Synovial fluid may be collected by syringe in a procedure termed arthrocentesis, also known as joint aspiration. Classification Synovial fluid may be classified into normal, noninflammatory, inflammatory, septic, and hemorrhagic : Classification of synovial fluid in an adult knee joint. Normal Noninflammatory Inflammatory Septic Hemorrhagic Volume ( ml ) < 3.5 > 3.5 > 3.5 > 3.5 > 3.5 Viscosity High High Low Mixed Low Clarity Clear Clear Cloudy Opaque Mixed Color Colorless / straw Straw / yellow Yellow Mixed Red WBC / mm < 200 < 2,000 5,000 - 75,000 > 50,000 Similar to blood level Polys ( % ) < 25 < 25 50 - 70 > 70 Similar to blood level Gram stain Negative Negative Negative Often positive Negative Glucose ( mg / dl ) concentration in synovial fluid is nearly equal to serum. Synovial fluid viscosity Normal : Normal Traumatic arthritis Degenerative ( Osteo ) arthritis Pigmented villonodular synovitis Normal or decreased : Systemic lupus erythematosus Decreased : Rheumatic fever Rheumatoid arthritis Gout Pyogenic ( Septic ) arthritis Tubercular arthritis Pathology Many synovial fluid types are associated with specific diagnoses : Noninflammatory ( Group I ) Osteoarthritis, degenerative joint disease Trauma Rheumatic fever Chronic gout or pseudogout Scleroderma Polymyositis Systemic lupus erythematosus Erythema nodosum Neuropathic arthropathy ( with possible hemorrhage ) Sickle - cell disease Hemochromatosis Acromegaly Amyloidosis Inflammatory ( Group II ) Rheumatoid arthritis Reactive arthritis Psoriatic arthritis Acute rheumatic fever Acute gout or pseudogout Scleroderma Polymyositis Systemic lupus erythematosus Ankylosing spondylitis Inflammatory bowel disease arthritis Infection ( viral, fungal, bacterial ) including Lyme disease Acute crystal synovitis ( gout ) Septic ( Group III ) Pyogenic bacterial infection Septic arthritis Hemorrhagic Trauma Tumors Hemophilia / coagulopathy Scurvy Ehlers - Danlos syndrome Neuropathic arthropathy Analysis Glucose ( mg / dl ) concentration in synovial fluid is nearly equal to serum. The cytological and biochemical analysis of human synovial fluid began around 1940 using cadaver - derived fluid and comparing characteristics to those of, for instance, bovine synovial fluid. Chemistry The mucin clot test is a very old approach to determining if an inflammatory infiltrate is present. In this test, acetic acid is added to the synovial fluid specimen. In a normal specimen, this should lead to a congealing of the hyaluronic acid, forming a ' mucin clot. ' If inflammation is present, a mucin clot is not formed ( the hyaluronic acid is degraded ). Lactate is elevated in septic arthritis, usually above 250 mg / dL. Complement factors are decreased in rheumatoid arthritis and lupus arthritis. Microscopy Microscopic analysis of synovial fluid is performed to evaluate for cell count and crystals. Crystals include monosodium urate, calcium pyrophosphate, hydroxyapatite and corticosteroid crystals. Monosodium urate crystals are seen in gout or gouty arthritis and appear as needle - shaped negatively birefringent crystals varying in length from 2 to 20 μm. With negative birefringence, the crystals appear yellow in parallel light and blue with perpendicular light. Calcium pyrophosphate crystals are seen in pseudogout ( also known as calcium pyrophosphate deposition disease or, CPPD ). These crystals are rod - shaped or rhomboids varying in length from 2 to 20 μm and with positive birefringence ( blue with parallel light, yellow with perpendicular light ). Hydroxyapatite crystals are small and negatively birefringent. They are usually only detectable with an Alizarin Red S stain. Corticosteroid crystals may be seen following therapeutic corticosteroid injection into the joint space. They appear blunt, jagged, and show variable birefringence. Cracking joints Main article : Cracking joints When the two articulating surfaces of a synovial joint are separated from one other, the volume within the joint capsule increases and a negative pressure results. The volume of synovial fluid within the joint is insufficient to fill the expanding volume of the joint and gases dissolved in the synovial fluid ( mostly carbon dioxide ) are liberated and quickly fill the empty space, leading to the rapid formation of a bubble. This process is known as cavitation. Cavitation in synovial joints results in a high frequency ' cracking ' sound. Etymology and pronunciation The word synovia ( / sɪˈnoʊviə / ) came to English from New Latin, where it was coined by Paracelsus. Several dictionaries indicate that the - ov - syllable of the word reflects the Ancient Greek ᾠόν ( ōión ) and Classical Latin ōvum, cognates that both mean `` egg '' ( which seems appropriate given the egg white -- like nature of synovial fluid ) -- thus syn - + oo - / ovo - + - ia -- although several others omit that aspect of the etymology, and one states, `` probably formed arbitrarily by Paracelsus. '' Whether true or false, the connection to ovum is still helpful to students as a memory device. Somewhat confusingly, the inflected form synovia can be either a principal ( and uncountable ) declined form referring to synovial fluid ( synovia ) or a second declined form as the plural of synovium ( thus `` synovial membranes '', synovia ). The avoidance of this ambiguity drives the use of the term synovial fluid to be more common than the use of its synonym synovia. References Jump up ^ West, Sterling G. ( 2015 ). Rheumatology secrets. The secrets series ( 3rd ed. ). Philadelphia : Elsevier Mosby. p. 19. ISBN 9780323037006. OCLC 908716294. Jump up ^ Bennike, Tue ; Ayturk, Ugur ; Haslauer, Carla M. ; Froehlich, John W. ; Proffen, Benedikt L. ; Barnaby, Omar ; Birkelund, Svend ; Murray, Martha M. ; Warman, Matthew L. ( 2014 - 09 - 03 ). `` A Normative Study of the Synovial Fluid Proteome from Healthy Porcine Knee Joints ''. Journal of Proteome Research. 13 ( 10 ) : 4377 -- 4387. doi : 10.1021 / pr500587x. PMC 4184458. PMID 25160569. Jump up ^ Jay GD, Waller KA ( 2014 ). `` The biology of lubricin : near frictionless joint motion ''. Matrix Biology. 39 : 17 -- 24. doi : 10.1016 / j. matbio. 2014.08. 008. PMID 25172828. Jump up ^ Edwards, Jo, ed. ( 2000 ). `` Normal Joint Structure ''. Notes on Rheumatology. University College London. Archived from the original on 19 November 2012. Retrieved 5 April 2013. Jump up ^ McCracken, Thomas, ed. ( 2000 ). New Atlas of Human Anatomy. China : MetroBooks. ISBN 9781586630973. OCLC 850877694. Jump up ^ Christorpher, GF. `` The role of protein content on the steady and oscillatory shear rheology of model synovial fluids ''. Royal Society of Chemistry. 2014 ( 10 ) : 5965 -- 5973. doi : 10.1039 / C4SM00716F. Jump up ^ `` Synovial fluid - OrthopaedicsOne Articles - OrthopaedicsOne ''. Retrieved 20 September 2016. Jump up ^ Sabaratnam S, Arunan V, Coleman PJ, Mason RM, Levick JR ( 2005 ). `` Size selectivity of hyaluronan molecular sieving by extracellular matrix in rabbit synovial joints ''. The Journal of Physiology. 567 ( Pt 2 ) : 569 -- 81. doi : 10.1113 / jphysiol. 2005.088906. PMC 1474196. PMID 15961430. Jump up ^ < Oates, Katherine ( 2006 ). `` Rheopexy of synovial fluid and protein aggregation ''. The Journal of the Royal Society Interface. 3 : 167 -- 74. doi : 10.1098 / rsif. 2005.0086. PMC 1618490. PMID 16849228. Jump up ^ Hui, Alexander Y. ; McCart, William J. ; Masuda, Koichi ; Firestein, Gary S. ; Sah, Robert L. ( Jan -- Feb 2012 ). `` A Systems Biology Approach to Synovial Joint Lubrication in Health, Injury, and Disease ''. Systems Biology and Medicine. Wiley Interdisciplinary Reviews. 4 ( 1 ) : 15 -- 7. doi : 10.1002 / wsbm. 157. PMC 3593048. PMID 21826801. Jump up ^ `` GlycoForum / Science of Hyaluronan ''. 15 December 1997. Jump up ^ `` Joints ''. University of Washington Medicine - Department of Orthopaedics and Sports Medicine. Retrieved 2013 - 02 - 04. Jump up ^ Jay, GD ; Britt, DE ; Cha, CJ ( March 2000 ). `` Lubricin is a product of megakaryocyte stimulating factor gene expression by human synovial fibroblasts ''. J Rheumatol ( abstract ). 27 ( 3 ) : 594 -- 600. PMID 10743795. Jump up ^ Warman M ( 2003 ). `` Delineating biologic pathways involved in skeletal growth and homeostasis through the study of rare Mendelian diseases that affect bones and joints ''. Arthritis Research & Therapy. 5 ( Suppl 3 ) : S2. doi : 10.1186 / ar804. ^ Jump up to : Table 6 - 6 in : Elizabeth D Agabegi ; Agabegi, Steven S. ( 2008 ). Step - Up to Medicine ( Step - Up Series ). Hagerstwon, MD : Lippincott Williams & Wilkins. ISBN 0 - 7817 - 7153 - 6. Jump up ^ `` Lupus Anticoagulant ''. Family Practice Notebook. Archived from the original on 18 January 2013. Retrieved 7 April 2013. Jump up ^ American College of Rheumatology Archived September 5, 2004, at the Wayback Machine. Jump up ^ Ropes, Marian W. ; Rossmeisl, Elsie C. ; Bauer, Walter ( November 1940 ), `` The Origin and Nature of Normal HUman Synovial Fluid '' ( scanned pages ), J Clin Invest, 19 ( 6 ) : 795 -- 799, doi : 10.1172 / JCI101182, PMC 435014, PMID 16694795, retrieved 6 April 2013 and references therein ^ Jump up to : De Mais, Daniel ( 2009 ), Quick Compendium of Clinical Pathology ( 2nd ed. ), Chicago : ASCP Press, ISBN 9780891895671, OCLC 692198047 Jump up ^ Unsworth A, Dowson D, Wright V ( 1971 ). `` ' Cracking joints '. A bioengineering study of cavitation in the metacarpophalangeal joint ''. Ann Rheum Dis. 30 ( 4 ) : 348 -- 58. doi : 10.1136 / ard. 30.4. 348. PMC 1005793. PMID 5557778. Jump up ^ Watson P, Kernoham WG, Mollan RAB. A study of the cracking sounds from the metacarpophalangeal joint. Proceedings of the Institute of Mechanical Engineering ( H ) 1989 ; 203 : 109 - 118. Jump up ^ `` What makes your knuckles pop ? ''. 3 August 2000. Retrieved 20 September 2016. ^ Jump up to : Merriam - Webster, Merriam - Webster 's Unabridged Dictionary, Merriam - Webster. ^ Jump up to : Houghton Mifflin Harcourt, The American Heritage Dictionary of the English Language, Houghton Mifflin Harcourt. ^ Jump up to : Oxford Dictionaries, Oxford Dictionaries Online, Oxford University Press. Jump up ^ Elsevier, Dorland 's Illustrated Medical Dictionary, Elsevier. Jump up ^ Wolters Kluwer, Stedman 's Medical Dictionary, Wolters Kluwer. Further reading Warman M., Delineating biologic pathways involved in skeletal growth and homeostasis through the study of rare Mendelian diseases that affect bones and joints, Arthritis research & therapy 2003, 5 ( Suppl 3 ) : 5, doi : 10.1186 / ar804. Accessed 2015 - 11 - 14. External links Hyaluronan : structure and properties Normal joint structure from the University College London Joints Types Fibrous Gomphosis Suture Syndesmosis Interosseous membrane Cartilaginous Synchondrosis Symphysis synovial : Plane joint 1 ° Hinge joint Pivot joint 2 ° Condyloid joint Saddle joint 3 ° Ball and socket joint synostosis by range of motion : Synarthrosis Amphiarthrosis Diarthrosis Terminology Kinesiology Anatomical terms of motion Agonist / Antagonist Motions general : Flexion / Extension Adduction / Abduction Internal rotation / External rotation Elevation / Depression specialized / upper limbs : Protraction / Retraction Supination / Pronation specialized / lower limbs : Plantarflexion / Dorsiflexion Eversion / Inversion Components capsular : Joint capsule Synovial membrane Fibrous membrane Synovial fluid Synovial bursa Articular disk / Meniscus extracapsular : Ligament Enthesis GND : 4156451 - 0 NDL : 00576163 Retrieved from `` https://en.wikipedia.org/w/index.php?title=Synovial_fluid&oldid=835435290 '' Categories : Body fluids Joints Hidden categories : Pages with unresolved properties Webarchive template wayback links Wikipedia articles needing page number citations from April 2013 All accuracy disputes Articles with disputed statements from December 2015 All articles lacking reliable references Articles lacking reliable references from February 2013 Articles containing Ancient Greek - language text Articles containing Latin - language text Wikipedia articles with GND identifiers Talk Contents About Wikipedia Català Deutsch Eesti Español Esperanto Euskara فارسی Français Ido Italiano Latviešu മലയാളം Nederlands 日本 語 Polski Português Русский Simple English کوردی Svenska தமிழ் Türkçe Українська 15 more Edit links This page was last edited on 8 April 2018, at 18 : 11. 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Question: where is synovial fluid found in the body
Answer: in the cavities of synovial joints