Articulations - Joints
Articulations relate the muscles to the bones, and also connect them and ensure the flexibility and the solidity. We describe here the elements which compose the mobile articulations, i.e. the large articulations which allow wide movements (knee, ankle, elbow, shoulder, hip, etc).
The articular cartilage: type of pearly and smooth fabric conjunctive, nonvascularized, which covers the bones with all the mobile articulations.
The articular capsule: fibrous envelope and rubber band which surrounds and delimits the mobile articulations. The articular capsules contribute, with the ligaments, to maintain in contact the structures of the articulation and to ensure its stability.
The synovial membrane: membrane which papers the internal face of the capsule of the mobile articulations. The synovial form of the folds has as a function to nourish and lubricate articular surfaces by producing a liquid, the synovial liquid.
Articular ligaments: conjunctive fabrics white fibrous, very resistant and elastic. The ligaments link between the bones.
The meniscus: small fibrocartilagineuse structure having the shape of a crescent (in the Greek mêniskos = growing), located between two mobile articular surfaces (they are found in the knee and the jaw). The meniscus forms a cushion in the articulation, which allows the intimate contact between surfaces and the slip of the articulation, just like the damping of the impacts.
Serous bursa: small closed pockets made up of conjunctive fabric filled with synovial liquid. The purses are fixed at the bones near the articulations and prevent the direct contact between a bone and a tendon, for example. Thus, they facilitate the slip of the structures and make it possible to deaden the movements.
Tendons: fibrous fabric little innerved (absence or quasi-absence of nerves) and little or not vascularized (absence of blood vessels), which connect the muscles to the bones that they must drive.
The types of articulations:
Joints can also be classified functionally, by the degree of mobility they allow.
Synarthrosis: permit little or no mobility. They can be categorized by how the two bones are joined together: Synchondroses are joints where the two bones are connected by a piece of cartilage. Synostoses are where two bones that are initially separated and can eventually fuse together, essentially becoming one bone. In humans the plates of the cranium fuse together as a child approaches adulthood. Children whose craniums fuse too early may suffer deformities and brain damage as the skull does not expand properly to accommodate the growing brain, a condition known as craniostenosis. Most synarthrosis joints are fibrous.
Amphiarthrosis: permit slight mobility. The two bone surfaces at the joint are both covered in hyaline cartilage and joined by strands of fibrocartilage. Most Amphiarthrosis joints are cartilaginous.
Diarthrosis: permit a variety of movements (e.g. flexion, adductio, and pronation). Only synovial joints are diarthrodial.
The effects of the repetitive movements on the articulations:
Although a specific accident (exceptional effort to raise a heavy object, extreme torsion, etc), a degenerative disease (arthritis rheumatoid, osteoarthritis, etc) or an infection can cause damage with one or the other of these fabrics, the most frequent cause of the hoop nets musculosquelettic remains to the practice of repetitive movements. These movements cause light traumatisms which, with long, end up damaging the fabrics which connect the muscles to the skeleton.
The tendonitis or inflammation of a tendon is a current demonstration of this type of problem. By repeating the same movements, part of the bone rubs on a tendon and causes more or less important lesions. While being long in looking after a tendonitis adequately, one is likely to cause damage with various fabrics and bodies which are in the vicinity. Thus, a tendonitis will be able to become complicated in case of the inflammation of a serous bursa, the inflammation of a synovial membrane, the inflammation of the tendon and the synovial membrane. The attack of the articular capsule, may lead to the blocking of the articulation. It can also happen that the fabrics reached compress and irritate certain nerves, as it is the case for the syndrome of repetitive stress injuries.
The problems of articulations may lead to dangerous diseases. So we must consider Arthritis and Arthrosis.
Arthritis: Arthritis, any of more than 100 different diseases causing pain, stiffness, and in most cases, swelling in the joints. Arthritis affects people of both sexes and of all races, socioeconomic levels, and geographic areas. Inflammatory types of arthritis are characterized by their tendency to cause inflammation in joints and tendons. In inflammatory arthritis, the synovial membrane becomes swollen and inflamed, causing pain and stiffness.
Osteoarthritis: The most common form of arthritis is osteoarthritis (OA), also known as degenerative joint disease. OA is most prevalent in people aged 55 and older, 80 percent of whom are women. In OA, the cartilage cushion in the joints breaks down, causing the bones to rub together. Pain, stiffness, and sometimes the formation of bone growths, called spurs, result.
Prevention is necessary in order to avoid the injuries and the diseases of articulations that may become dangerous.
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