Synovial fluid is a thin, stringy fluid found in the cavities of synovial joints. With its egg-like consistency (synovial comes from Latin for "egg"), synovial fluid reduces friction between the articular cartilage and other tissues in joints to lubricate and cushion them during movement. This article is about a joint in zootomical anatomy. ... Latin was the language originally spoken in the region around Rome called Latium. ... Look up egg in Wiktionary, the free dictionary. ... Cartilage is a type of dense connective tissue. ...

Overview

The inner membrane of synovial joints is called the synovial membrane, which secretes synovial fluid into the joint cavity. This fluid forms a thin layer (approximately 50 micrometres) at the surface of cartilage, but also seeps into the articular cartilage filling any empty space [1]. The fluid within articular cartilage effectively serves as a synovial fluid reserve. During normal movements, the synovial fluid held within the cartilage is squeezed out mechanically (so-called weeping lubrication) to maintain a layer of fluid on the cartilage surface. The synovium or synovial membrane is a thin, weak layer of tissue which lines the non-cartilaginous surfaces within the joint space, sealing it from the surrounding tissue. ... A micrometre (American spelling: micrometer), symbol µm, is an SI unit of length. ...

Composition

Normal synovial fluid contains 3-4 mg/ml hyaluronan (hyaluronic acid), a polymer of disaccharides composed of D-glucuronic acid and D-N-acetylglucosamine joined by alternating beta-1,4 and beta-1,3 glycosidic bonds [2]. Hyaluronan is synthesized by the synovial membrane and secreted into the joint cavity to increase the viscosity and elasticity of articular cartilages and lubricate the surfaces between synovium and cartilage [3]. Hyaluronan (also called hyaluronic acid or hyaluronate) is a glycosaminoglycan distributed widely throughout connective, epithelial, and neural tissues. ... A disaccharide is a sugar (a carbohydrate) composed of two monosaccharides. ... Chemical structure of α-D-glucosamine Glucosamine (C6H14NO5) is an amino sugar that is a biochemical precursor in the synthesis of glycosaminoglycans. ... In chemistry, a glycosidic bond is a certain type of chemical bond that joins a sugar molecule to another molecule. ...

Synovial fluid also contains lubricin secreted by synovial cells. It is chiefly responsible for so-called boundary-layer lubrication, which reduces friction between opposing surfaces of cartilage. There is also some evidence that it helps regulate synovial cell growth [4]. Lubricin is a glycoprotein encoded by the PRG4 gene. ...

Health and disease

Classification

Synovial fluid can be classified into normal, noninflammatory, inflammatory, septic, and hemorrhagic:

An x-ray of a human knee In human anatomy, the knee is the leg joint connecting the femur and the tibia. ... The pitch drop experiment at the University of Queensland. ... White Blood Cells redirects here. ... Gram staining is a method for staining samples of bacteria that differentiates between the two main types of bacterial cell wall. ...

Pathology

Many synovial fluid types are associated with specific diagnoses [5] [6]:

• 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
  • Reiter's syndrome
  • Psoriatic arthritis
  • Acute rheumatic fever
  • Acute gout or pseuodgout
  • Scleroderma
  • Polymyositis
  • Systemic lupus erythematosus
  • Ankylosing spondylitis
  • Inflammatory bowel disease arthritis
  • Infection (viral, fungal, bacterial)
  • Acute crystal synovitis
• Septic (Group III)
  • Pyogenic bacterial infection
  • Septic arthritis
• Hemorrhagic
  • Trauma
  • Tumors
  • Hemophilia/coagulopathy
  • Scurvy
  • Ehlers-Danlos syndrome
  • Neuropathic arthropathy

Osteoarthritis (OA, also known as degenerative arthritis or degenerative joint disease, and sometimes referred to as arthrosis or osteoarthrosis), is a condition in which low-grade inflammation results in pain in the joints, caused by wearing of the cartilage that covers and acts as a cushion inside joints. ... Osteoarthritis (OA, also known as degenerative arthritis or degenerative joint disease, and sometimes referred to as arthrosis or osteoarthrosis), is a condition in which low-grade inflammation results in pain in the joints, caused by wearing of the cartilage that covers and acts as a cushion inside joints. ... Rheumatic fever is an inflammatory disease which may develop after a Group A streptococcal infection (such as strep throat or scarlet fever) and can involve the heart, joints, skin, and brain. ... It has been suggested that this article or section be merged with Calcium pyrophosphate deposition disease. ... Scleroderma is a rare, chronic disease characterized by excessive deposits of collagen. ... Polymyositis A type of Inflammatory Myopathy, related to Dermatomyositis and Inclusion body myositis. ... Erythema nodosum is a form of inflammation of the subcutaneous fatty tissue. ... An arthropathy is a disease of a joint. ... Sickle-shaped red blood cells Sickle cell disease is a general term for a group of genetic disorders caused by sickle hemoglobin (Hgb S). ... Haemochromatosis, also spelled hemochromatosis, is a hereditary disease characterized by improper processing by the body of dietary iron which causes iron to accumulate in a number of body tissues, eventually causing organ dysfunction. ... Rondo Hatton, a famous sufferer of acromegaly whose face was distorted by the disorder. ... Rheumatoid arthritis (RA) is a chronic, inflammatory autoimmune disorder that causes the immune system to attack the joints. ... It has been suggested that this article or section be merged with Reactive arthritis. ... Psoriatic arthritis (or Arthropathic psoriasis) is a type of inflammatory arthritis that affects around 20% of people suffering from the chronic skin condition Psoriasis. ... Infected (Podcast) is also the name of an internet radio podcast hosted by Martin Sargent. ... Septic arthritis is the proliferation of bacteria in joints and resultant inflammation. ... Tumor (American English) or tumour (British English) originally means swelling, and is sometimes still used with that meaning. ... Haemophilia or hemophilia is the name of any of several hereditary genetic illnesses that impair the bodys ability to control bleeding. ... This page is a candidate to be moved to Wiktionary. ... Scurvy is a disease that results from insufficient intake of vitamin C and leads to the formation of livid spots on the skin, spongy gums, and bleeding from almost all mucous membranes. ... Ehlers-Danlos syndrome is a group of rare genetic disorders that diminish the bodys ability to make connective tissues. ...

External links and references

• How are joints lubricated?, from University of Washington Medicine
• Warman W. "Delineating biologic pathways involved in skeletal growth and homeostasis through the study of rare Mendelian diseases that affect bones and joints." Arthritis Res. Ther. 2003, 5(Suppl 3):5 [7]
• Hyaluronan: structure and properties
• Synovial fluid analysis, from the American College of Rheumatology
• Synovial fluid white blood cell count, from the Family Practice Notebook
• Synovial fluid, from the FPN
• Normal joint structure, from University College London