The Synovia is also known as synovial fluid and has a high viscosity. In addition to the nutrition of the joint, her duties include the reduction of friction on the articular surfaces. In joint diseases such as osteoarthritis changes the composition of the synovial fluid.

What is the Synovia?

With the term Synovia the physician refers to the lubricating fluid in real joints. This synovial fluid also occurs in tendon gliding devices such as bursae and tendon sheaths and is formed by the synovial membrane. It is the inner layer of the joint capsule of a joint. On the articular surfaces, the Synovia forms a film that ensures smooth gliding.

The term has been around since the 16th century. At that time, the physician and alchemist Paracelsus composed him from the Greek conjunction "syn" and the noun "ovia" for protein. Translated literally synovia means "together with protein". This designation already gives indications of the composition of the viscous liquid. Not all joints contain the same amount of synovia. The amount varies with the expected friction.

Anatomy & Construction

The synovium of a healthy joint is viscous, yellowish and clear. 94 percent of the liquid consists of water. The pH of the synovial fluid is around 7.5. Synovia is obtained from the blood plasma. Their electrolyte composition was therefore very similar to that of plasma. Both different plasma proteins as well as plasma enzymes and acid phosphatase are present.

Plasma proteins include both albumins and globulins. As a relic of the synovial membrane, the fluid also contains mucilages such as hyaluronic acid. This acid first gives the synovial fluid its viscosity through pressure resistance, water binding capacity and adhesion effects. Glucose and glycosaminoglycans ensure a different viscosity depending on the load.

Function & Tasks

The Synovia mainly fulfills two functions. First, it nourishes the articular cartilage with glucose. On the other hand occur through the liquid less friction forces. In addition, the viscous mixture provides a shock absorber effect, ensuring that the joints are not damaged. Without Synovia, the joints in the human body would show signs of wear after a very short time and thus dissolve piece by piece.

The viscosity of the synovial fluid changes with the load applied. The hyaluronic acid is responsible for this. For example, as the shear forces increase, the viscosity of hyaluronic acid decreases and thus balances. Since the acid is actually liquid, the synovial fluid remains high-molecular in shape. Due to this high-molecular form, the viscosity is sufficient to avoid water losses due to pressure movements in the joint. Because of chemical interactions, hyaluronic acid adheres ideally to the cartilage of a joint. Depending on the movement, the molecules in the grease bind together in spherical form as soon as strong pressure forces act on the joint. As balls they hang on the surface of the articular cartilage.

This feature is especially important for movements like jumping. With fast movements or sudden shearing movements, the toughness of the synovial fluid is reduced. This reduction reduces the friction in the joint. Thus, the synovial fluid protects each joint from wear and high loads, as it adapts to the respective movement and can change its shape within seconds. The fluid exchange and the cartilage nutrition takes place by changing debits and loads. If a joint has to be immobilized for a long time, this coordinated system of burdens and reliefs will be disturbed. As a result, the nutrition of the articular cartilage is disturbed. Therefore, cartilage damage occurs due to malnutrition.

Diseases

The synovium can change in its composition and amount pathologically. Such a phenomenon is present for example in diseases such as osteoarthritis, but also in other joint diseases. It is a degenerative joint disease. On all joint changes, the organism reacts with excessive production of Synovia. This phenomenon is also known as joint hydrops and may be due to an inflammatory process in the joint or after a wear and tear in the joints.

Because of the excess of synovial fluid, the joint now swells from the outside swollen. Either there is an actual effusion or swelling of the capsule. At the same time as overproduction, the Synovia also changes its composition. The synovial fluid becomes more watery. Either the fluid becomes cloudy due to cell abrasion or it even turns dark due to bleeding. If hemorrhages are present, the synovium even acts aggressively on the articular cartilage. Due to the lost viscosity, the synovial fluid can no longer fulfill its tasks from now on.

If there are no color changes and the synovial fluid is still clear, there are nevertheless functional losses. The capsule of the joint may overstretch in a consequence of this. The speech is then also of an eruption, as it occurs in the context of osteoarthritis all too often. Puncture can drain the fluid from the affected joint. The laboratory analysis of the drained fluid may show various changes in the composition of the synovium. In arthritis inflammation can be detected via the synovial fluid. In the case of gout, there are indications in the laboratory analysis of a disturbance of the uric acid metabolism.

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