Synovial Fluid Lecture Notes PDF

SYNOVIAL FLUID 1  PHYSIOLOGY  Referred to as “joint fluid,” is a viscous mucinous liquid found in the cavities of the movable joints (diarthroses) or synovial joints  It is lubricates most joints.  The joint is enclosed in a fibrous joint capsule lined by the synovia...

SYNOVIAL FLUID 1  PHYSIOLOGY  Referred to as “joint fluid,” is a viscous mucinous liquid found in the cavities of the movable joints (diarthroses) or synovial joints  It is lubricates most joints.  The joint is enclosed in a fibrous joint capsule lined by the synovial membrane.  The synovial membrane contains specialized 2 cells called synoviocytes. Diagram of a synovial joint 3 4  COMPOSITION AND FORMATION  It is an ultrafiltrate of plasma across the synovial membrane.  Then the synoviocytes secrete a muco- polysaccharide containing hyaluronic acid and a small amount of protein into the fluid (noticeable viscosity).  Contains:  Hyaluronic acid  Muco-polysaccharides  Limited amount of plasma protein (approximately one fourth 5 of the plasma concentration)  Glucose & uric acid levels equivalent to plasma  SYNOVIAL FLUID  Functions:  Supplies nutrients to the articular cartilage  Lubrication of joint (reduce friction between the bones during joint movement)  Reasons for analysis:  Infection  Hemorrhage  Degenerative disorders (arthritis) 6  Inflammatory disease (SLE)  SYNOVIAL FLUID  Collection  Arthrocentesis 7  SYNOVIAL FLUID COLLECTION  The amount of fluid varies with the size of the joint i.e. the normal amount of fluid in the adult knee cavity is less than 3.5 mL, but can increase to greater than 25 mL with inflammation.  Normal synovial fluid does not clot; however, fluid from a diseased joint may contain fibrinogen and will clot. 8  SYNOVIAL FLUID COLLECTION  Tubes:  A sterile heparinized tube for Gram stain and culture  Ethylenediaminetetraacetic acid (EDTA) tube for cell counts (hematology)  A nonanticoagulated tube for crystal evaluation and chemistries, immunological tests 9  A sodium fluoride tube for glucose analysis 10  CLASSIFICATION OF SYNOVIAL FLUID  Normal  Non-Inflammatory  Degenerative joint diseases  Inflammatory  Immunologic disorders (i.e. lupus, RA, gout crystals, etc)  Septic  Microbial infections  Hemorrhagic 11  Traumatic injury, tumors, hemophilia, anticoagulant overdose, etc.  SYNOVIAL FLUID COLOR AND CLARITY  Normal color & clarity:  Colorless to pale yellow (straw) & clear  The word “synovial” comes from the Latin word for egg. Normal viscous synovial fluid resembles egg white.  Abnormal colors/ clarity:  Bloody  Hemarthrosis  Traumatic tap  White / opaque with turbidity  Indicate pus cells or debris 12  Xanthochromia term not used  PHYSICAL PROPERTIES VISCOSITY  Comes from the polymerization of the hyaluronic acid (hyaluronate).  Essential for the proper lubrication of the joints.  Screening Methods: 1) String Test:  Evaluates viscosity by observe the ability of the fluid to form a string (hang) from the tip of a syringe or pipette.  Normal = 5 cm long before breaking (4 to 6 cm is considered normal). 2) Rope’s test (mucin clot):  Add 2% to 5% acetic acid to synovial fluid (a solid clot surrounded by clear fluid will be form).  measures degree of hyaluronate polymerization.  Reported in terms of:  Good / normal (solid clot)  fair (soft clot) 13  Poor = appears friable or fails to form clot (no clot).  SYNOVIAL FLUID (HEMATOLOGY)  Cell Counts:  0 RBCs / uL  50): Staph. Aureus  Serology:  Serum results more reliable, so not often done for diagnosis of RA or LE 22  Autoantibodies 23