Synovial Fluid
Synovial fluid has many very important roles in the operation of a synovial joint. As discussed in the synovial joint section it sits in cavity around the articulated cartilage. The cavity is surrounded by a synovial membrane which hold the synovial fluid in place when joint is under pressure. The synovial membrane also called the synovium can be split into two layers, the synoviam and sub-synoviam as seen in the picture below of knee joint.
Synovial Sack
The Synovium is made up of Macrophage type A cells secretes the active lubricants into the synovial fluid while the sub-synovium made up of fibroplasts type B cells which filtrates out all the undesirable substances out of the synovial fluid into the blood stream. Lubricants are also secreted from the cartilage into the synovial fluid from the crondocytes. So when the cartilage is degraded from arthritis the synovial fluid undergoes mechanical and chemical degradation. This interdependency is talked about in many papers. The diagram above came from a paper by ME Blewis et al.’s. In this paper they mapped out how synovial fluid acts as a biochemical pool to which the nutrients are transferred into the cartilage and undesirable particulates are removed and passed out through subsynovium into the blood. Oxygen and nutrients move from the blood down the diagram into the cartilage while waste coming from the cartilage moves up the diagram into the blood which is outside the synovium.
The Synovium is made up of Macrophage type A cells secretes the active lubricants into the synovial fluid while the sub-synovium made up of fibroplasts type B cells which filtrates out all the undesirable substances out of the synovial fluid into the blood stream. Lubricants are also secreted from the cartilage into the synovial fluid from the crondocytes. So when the cartilage is degraded from arthritis the synovial fluid undergoes mechanical and chemical degradation. This interdependency is talked about in many papers. The diagram above came from a paper by ME Blewis et al.’s. In this paper they mapped out how synovial fluid acts as a biochemical pool to which the nutrients are transferred into the cartilage and undesirable particulates are removed and passed out through subsynovium into the blood. Oxygen and nutrients move from the blood down the diagram into the cartilage while waste coming from the cartilage moves up the diagram into the blood which is outside the synovium.
Arthritus
The role that synovial fluid has in the joint has been discussed but not what gives it these qualities. The physical constituents of synovial fluid is a big subject of study and has a large amount of literature on it. This is because tracking the ratios of substances contained in synovial fluid is a good way of mapping the effect and causes of such degenerate diseases and possibly develop treatments. The main cause of joint degeneration is by some sort of arthritis.The two main types are Osteoarthritis which is break-down of cartilage by wear and tear usually brought around by excessive use or damage to the joint and Rheamatoid arthritis which is an autoimmune desease where the synoviam is attacked by the bodys own cells. The effects of each can be seen in the diagram below. Around 10 million people in the U.K are thought to have arthritis of some form.
The role that synovial fluid has in the joint has been discussed but not what gives it these qualities. The physical constituents of synovial fluid is a big subject of study and has a large amount of literature on it. This is because tracking the ratios of substances contained in synovial fluid is a good way of mapping the effect and causes of such degenerate diseases and possibly develop treatments. The main cause of joint degeneration is by some sort of arthritis.The two main types are Osteoarthritis which is break-down of cartilage by wear and tear usually brought around by excessive use or damage to the joint and Rheamatoid arthritis which is an autoimmune desease where the synoviam is attacked by the bodys own cells. The effects of each can be seen in the diagram below. Around 10 million people in the U.K are thought to have arthritis of some form.
Synovial Fluid Compostion
The main constituent of synovial fluid is simply filtrated blood plasma taken through the synovial membrane so it must be the additives that gives it its unique physical characteristic. The other additives to plasma and there roles in the functioning of the joints is discussed in a lot of literature. The other constituents of synovial fluid are:
-Hyaluronic acid(HA)
-Lubricin a mucinous glycol-protein encoded by the gene proteoglycan 4.
-Proteins Albumin
-Protein Globulin which bind to HA)
-Surface active phospholids.
Rheological Properties
Synovial fluid is a non-newtonian fluid which demonstrates a shear-thinning or a Pseudoplastic effect. This means with increased shear rate the liquid becomes less viscous. This facilitates the smooth movement in the joint when its moving. The different non-newtonian properties can be seen on the shear stress shear rate graph below.
The main constituent of synovial fluid is simply filtrated blood plasma taken through the synovial membrane so it must be the additives that gives it its unique physical characteristic. The other additives to plasma and there roles in the functioning of the joints is discussed in a lot of literature. The other constituents of synovial fluid are:
-Hyaluronic acid(HA)
-Lubricin a mucinous glycol-protein encoded by the gene proteoglycan 4.
-Proteins Albumin
-Protein Globulin which bind to HA)
-Surface active phospholids.
Rheological Properties
Synovial fluid is a non-newtonian fluid which demonstrates a shear-thinning or a Pseudoplastic effect. This means with increased shear rate the liquid becomes less viscous. This facilitates the smooth movement in the joint when its moving. The different non-newtonian properties can be seen on the shear stress shear rate graph below.
The binding of the HA and proteins is thought to increase the visco-elactic effect of the HA. Hyuluronic acid as well as Lubricin are thought to be the main part of synovial fluid which gives SF its low friction and low ware properties. A good indication of HA affects on lubrication was Endre A balaz. In this paper they talk about how the decreases in levels of HA with age. The effects of this decrease in HA were studied and it was found that the viscoelastic effects as well as lubrication of the SF were diminished with loss of HA. . It was found that lubricin help SF dissipate strain as well as working synergistically with HA at providing lubrication on the cartilage boundary layer.