3- Synovial Fluid Flashcards
Where is the synovium in the axial skeleton?
joints, tendon sheaths, and bursae
What is a Type A Synoviocyte?
i) Contain lysosome and remove debris in joints ii) Macrophage-like, derived from hematopoietic system
What is a Type B Synoviocyte?
i) Secrete hyaluronic acid ii) Fibroblastic in nature, derived from mesenchyme
What is the anatomical makeup of the synovium?
a) The synovium is usually 2-4 layers thick b) Synoviocytes cover structures subject to pressure and are spread out c) Loose cellular connections make the synovial lining semipermeable
What is the topography of the synovium?
the lining consists of multiple villi and microvilli resulting in large surface area
How does the articular cart get it’s metabolites?
synovial fluid provides the means of metabolite delivery. The large surface area and semipermeable nature of synovium allows for delivery of nutrients.
What is the fxn of the synovial fluid?
Deliver nutrients to the articular cart.
How is synovial fluid made?
It is formed by the filtration of capillary plasma through a sieve of hyaluronate molecules, allowing small molecule to pass through.
What special thing does synovial fluid NOT have that prevents it from clotting?
fibrinogen (it’s too large to get in)
Is synovial fluid viscous or not very viscous?
Very viscous (<– try saying that 10x fast)
What substance causes the synovial fluid to be so viscous?
Hyaluronic acid
What is synovitis?
inflammation of synovial lining from inflammatory or non-inflammatory joint disease
What is bacterial septic arthritis?
most common monoarticular inflammatory arthritis. Inflammatory cells will release proteolytic enzymes that lead to rapid cartilage destruction
How many PMN’s do you need to confirm a bacterial septic arthritis Dx on arthrocentesis?
>50,000/mm3
What is the pathological process in rheumatoid arthritis (RA)?
deposition of Ag-Ab complexes w/in the synovium causes an inflammatory rxn that perpetuates a vicious cycle that causes joint destruction, starts in small joints of hands and feet and moves to larger joints
What happens to the synovial cells in RA?
Hypertrophy and hyperplasia of synovial cells produce thickening of synovial membrane
What happens to the synovial architecture in RA?
synovium to appear dense with a papillary architecture
What is the presentation of RA?
i) Early on it manifests as edema and chronic inflammation of the synovium. ii) Later, as RA progresses subsynovial fibroblasts proliferate and deposit collagen fibers which forms the pannus. Eventually there is complete destruction of the articular cartilage, creating the “burnt out” joint, which may be fused by either fibrous or bony ankylosis.
What is the pannus?
A proliferation of synovium beginning at the periphery of the joint surface
What is the etiology of osteoarthritis (OA)?
slowly progressing degenerative joint disease that is associated with aging w/ an unknown etiology
What is the pathophysiology of OA?
OA is caused by destruction of cartilage (compared to RA in which the synovium is also destroyed). Synovitis does occur, but is a result of cartilage destruction
What is effusion?
the increase in intra-articular fluid.
What causes effusion?
occurs when lysosomal enzymes of inflammatory cells break down the hyaluronic acid sieve barrier allowing large proteins to enter the synovial fluid.
How can clots form when there is an effusion?
the hyaluronic acid barrier is broken down, larger molecules like fibrinogen can enter the synovial fluid and cause clots.
Why is viscosity decreased when there is an effusion?
Since the viscosity of the fluid depends on [hyaluronic acid], as the hyaluronic acid is broken down its concentration dec so does the synovial fluid viscosity.
Identify general characteristics of synovial fluid in different types of effusions. These include color, clarity, viscosity, WBC, glucose, crystals.

What are the 4 examples of benign synovial tumors?
Hemangiomas, lipomas, pigmented villonodular synovitis, and synovial chondromatosis
What is primary synovial chondromatosis?
a condition in which hyaline cartilage nodules grow w/in the synovial lining of a joint, bursa, or tendon sheath.
In this form the nodules of cartilage form de novo and are of hyaline cartilage, these nodules may calcify and form lamellar bone.
What are the findings in primary synovial chondromatosis?
(1) Most common between 30-50, men are twice as affect as women
(2) Unilateral knee joint is most commonly affected
(3) Sx: pain, swelling, and mechanical symptoms (locking/giving way)
(4) Exam: effusion, palpable mass, tenderness, soft-tissue swelling, muscle atrophy and crepitus.
What are secondary synovial chondromatosis?
cartilaginous nodules that form may detach and become loose bodies, which produces joint debris that sticks to synovium