Synovial fluid


The synovial fluid, in medical terms Synovia and known colloquially as “synovial fluid”, it is a viscous and clear fluid that is present in the joint cavities. It is formed by the mucous membrane of the joint capsule and serves to reduce the frictional forces during joint movements and to supply the joint cartilage with nutrients. In addition, the synovia is also contained in bursae and tendon sheaths.

Formation of the gel fluid

The Synovial fluid (Synovia) is used by the so-called Synoviocytes educated. They are also known as synovial cells and clothe the synovial membrane, also called Synovium or Synovial membrane, out. The synoviocytes differ greatly in their appearance and a basic distinction is made between two types: Type A and Type B. The cells of type A tend to have a degrading function in that they absorb and dissolve cell debris and other debris. Those of type B are the actual and producing synoviocytes. They put out a mix Hyaluronic acid, Collagen and Fibronectin the latter two being important components of the synovial membrane itself.

The Hyaluronic acid, also Hyaluronan called, is together with water and other mucus-forming products of the synoviocytes the main component of the synovial fluid and ensures its viscosity.

In addition, the Synovia still Electrolytes and enzymes which come from the blood plasma together with the water.

Function of the synovial fluid

As already mentioned, the synovial fluid has two important functions. On the one hand, it serves the Reduction of friction with joint load and beyond the Vsupply of the articular cartilage with nutrients and oxygen.

This is especially important for the viscosity Hyaluronan responsible. It binds water and transforms it into a more viscous mass, which is not simply pressed out of the joint space under load, but remains there. This largely prevents the two joint surfaces from meeting directly. Interestingly, the Synovia nor the property that their viscosity decreases with shear movements, so that it can serve as a lubricant, for example, with fast movements that trigger high shear forces.

Its second important function is to nourish the articular cartilage. The articular cartilage is not permeated by vessels and is therefore not supplied with blood. Both nutrients and oxygen can therefore only be sent via diffusion get from the synovial fluid into the cartilage. This is only possible because tissues such as cartilage or ligaments have a very slow metabolism and therefore do not have a high demand for these substances. The property of slow metabolism is also called bradytroph designated.

Synovial inflammation

The Synovial inflammation, also Synovitis called, describes a painful and swelling reaction of the body in the area of ​​the synovial membrane (synonyms: Synovium or Synovial membrane). The joint may become red and overheated. In addition, fluid can also build up and lead to joint effusion. The function of the joint can be impaired and a Stiffness of the affected joint can occur.

An inflammation of the synovial membrane can have a variety of causes. Fall under it

Trauma, autoimmune and metabolic diseases, Infections and wear-related inflammation.

Trauma, i.e. physical damage caused by a fall or impact, for example, can trigger the inflammation. Advanced osteoarthritis can also cause the cartilage and bones to rub, causing inflammation.

An infestation of a joint by a bacterial or viral pathogen also triggers an immunological response, whereby both the pathogen itself and the resulting reaction can cause lasting damage to the joint.

Autoimmune diseases like that Rheumatoid arthritis or the Psoriatic arthritis also attack the joints and loosen one there Inflammation (inflammation) out. Metabolic diseases like that too gout lead to inflammation and destruction of the affected joint by depositing crystals there, which then activate the immune system.

Therapy should be anti-inflammatory and address the cause.

It is important to note that synovial inflammation of any kind can destroy a joint as the immune response releases enzymes and recruits cells that can also destroy healthy tissue.

Joint effusion

A Joint effusion comes about because there is too much fluid in the joint capsule. This can have various causes. In principle, every inflammation leads to an increased accumulation of fluid and thus to an effusion. Hence all the causes play out Synovial inflammation also play a role in the development of joint effusion. In addition, incorrect loading and other diseases such as a tendency to bleed or local tumors can lead to swelling of the joint.

Depending on the cause of the joint effusion, the fluid, which by means of a Puncture can be obtained from the joint, different compositions. Normal synovia is clear and viscous. At bacterial inflammation it can be purulent and yellow. A bruise trauma or a tendency to bleed leads to a reddish discoloration.

The diagnosis includes clarifying the cause and, if necessary, a puncture is performed. On the one hand, this can help diagnose the cause, but at the same time it can also be therapy by relieving pressure on the joint capsule.

Treatment includes correcting the cause, a Immobilization and rest of the joint with subsequent remobilization and, if necessary, a puncture to relieve pressure.

Build up synovial fluid

Since the synovial fluid is a filtrate of the blood, care should be taken that the body enough liquid available, in other words: enough drank becomes.

Since cigarette smoke worsens the blood flow in small vessels, it also means that the synovial fluid is less able to get nutrients and its quality decreases. A Smoking cessation therefore makes sense.

In the case of complaints that cannot be remedied by physiotherapy and other conservative methods, there is also the possibility of applying substances directly into the joint cavity, i.e. injecting them. examples for this are Polynucleotide gel and Hyaluronic acid. Both substances are supposed to increase the fluidity of the synovia and thus reduce friction and the development of pain. However, both therapies work Not covered by the statutory health insurance.

Pain and synovial fluid

If more synovial fluid is formed than is taken up again, the volume in the joint capsule increases and can increase Tension and pressure pain to lead. The causes are varied and have already been described above. The therapy options are limited to eliminating the cause of the increased formation and, if necessary, relieving the joint by means of a puncture. Against the pain you can pain reliever drugs can be used.