A joint is typically thought of as the connection between two bones, but a joint is made up of so much more than just bones. Without the surrounding structures of the bones, movement in the joint would not look as harmonious as usual for a long time, but rather "awkward".
In addition to the bones involved, most of the joints in our body also consist of joint cartilage, synovial fluid and the joint capsule. They all work together to create the beautiful, gliding movements of a joint that we all know from our own joints.
Of the cartilage serves as mechanical shock absorber on the ends of the bones so that they don't rub against each other, which would wear them out pretty quickly. also the cartilage evens out inequalities between the bones in the joint. The most famous example of this is the Thigh- and Lower leg bones, because the bone ends fit in Knee joint only because of the often tearing meniscus cartilage so perfectly together.
There bones in his End area very poor circulation is and Cartilage itself much fewer or even no blood vessels the cartilage must be nourished differently, because the cartilage cells also need nutrients to perform their tasks. Your Nutrition takes place through the synovial fluidthat in addition to their nutritional function have another Shock absorber and a sliding layer represents. This is where the joint capsule comes into play. You ucloses the joints like a kind of bag and keeps all the structures inside you hidden and protected. It consists of several Layers and cell types of which the innermost among other things for the Production of synovial fluid responsible is.
Viewed from the outside in, the joint capsule consists of different layers and structures that have different tasks in the joint. The outermost layer forms the so-called Membrana fibrosa, in German "fibrous skin". It consists of very coarse fibers of connective tissuethat give the capsule a certain strength to lend. Depending on the joint, the thickness of this skin be very different from very thin on small jointslike that Finger joints, up to several millimeters thick in the hip joint.
This layer of the joint capsule is still partially reinforced to really tight bandswhich bring additional stability. Examples of this are Inner and outer ligament in the knee joint as reinforcement of the knee joint capsule. But even without the ligaments, this outer layer of the joint capsule gives a joint strength and can Limit the range of motion of a joint.
In addition to the connective tissue fibers also run many nerve fibers within this outer layer. Among the nerve cells are, among other things, cells that the Measure the position of the jointso that we always know how the joint is in space even if we cannot see the body parts. This ability is noticeable, for example, when you use the eyes closes and then can still say exactly in which position the poor or legs are in the moment. But not only the nerve fibers for the sense of position, also those for the Pain perception lie here in the joint capsule. Because of this, are Capsule and ligament tears so extremely painful, whereas pure cartilage damage is hardly noticeable, because Cartilage is insensitive to pain.
The inner layer of the joint capsule forms the Synovial membrane. She is a lot more tender than the outer layer and contains different types of cells. On the one hand, they sit on the inside Cells that produce the joint fluid (= synovia), on the other hand, there are cells that contain the Recapture synovial fluid. These cells thus ensure that the space in the joint capsule, i.e. also between the bones, is always free of abrasion products from the cartilage or bones clean liquid reproduced becomes.
At arthrosis, the joint wear and tear, the constantly increased abrasion irritates the fluid-producing cells in the inner skin of the joint capsule in such a way that they constantly produce fluid and that The balance between the inflow and outflow of synovial fluid is massively disturbed becomes. The Capsule swells and restricts joint mobility. Worry too irritating substances in the liquid for that Inflammation and pain of the joint capsule, the affected one arthrosis mostly torment.
The inflammation leads to over a longer period of time Shortening of the connective tissue and the mobility of the joint will thus be increasingly restricted until the joint is in End stage osteoarthritis mostly replaced must become.