Joint

A joint ( articulatio Latin, Greek ἄρθρον Arthron ) from an anatomical point of view, a movable connection of two or more bones.

Fusing these bones, is spoken by a synostosis. The distinction is made between real anatomy that is provided with a liquid- filled gap, and false joints. With a pseudo joint, however, the remaining movable bone area is meant for a unhealed fracture.

Operations and effects in the interior of a joint to be referred to as intra-articular (e.g., intra-articular injection, administration of drugs by puncture of the joint). An arthroscopy is called arthroscopy.

• 3.1 names for movements

Loggerhead joints ( Synarthrosen )

Among the fake joints include:

• Cartilaginous bone compounds ( Juncturae or articulationes cartilagineae ) Synchondrosis Compound over hyaline cartilage, costal cartilage, for example,
• Symphysis: Connection via fibrocartilage, such as intervertebral discs

• Suture ( suture ), for example, between skull bones
• Syndesmosis ( tape adhesive ), for example, between the radius and ulna
• Gomphosis ( impaction ), solely for anchoring a tooth in the tooth socket ( dento - alveolar Arcticulatio )

True joints ( Diarthrosen )

In the synovial joints (also Diarthrosen or Juncturae synovial synovial or articulationes ) is located between the bone ends, a gap of joint space. The joint surfaces are covered with articular cartilage. To the joint is a joint capsule. It consists of a

• Outer membrane fibrosa ( tight connective tissue)
• Inner synovial membrane ( a epithelähnlicher Bindegewebsverband )

Gains of the membrana fibrosa form the joint capsule or ligaments. But ligaments may also be independent of connective tissue, which is outside of the joint capsule ( extracapsular ligaments, for example, the outer band of the knee joint ), in the wall of the joint capsule (eg, the inner band of the knee joint ) or within the joint cavity ( intracapsular ligaments, for example, the can be located cruciate ligaments of the knee joint ). The latter are coated with a layer of the synovial membrane, which is in connection with the joint capsule. Thus, the cruciate ligaments are intracapsular strictly true, but since they are not accessible from the joint cavity forth directly without passage of the synovial membrane, this can also be regarded as extra-articular.

The joint capsule forms a closed cavity around the joint cavity. It is filled with a viscous fluid, synovial fluid ( " synovial fluid " ), which is a product of the synovial membrane of the joint capsule.

Joint forms

According to the shape of the articular surfaces, the real joints can be further subdivided:

• Ball joint ( articulatio sphaeroidea ): three-axis, eg shoulder joint, hip joint, metacarpophalangeal joints (except the thumb); can be moved around the three orthogonal axes: flexion - extension, abduction and adduction, external and internal rotation.
• Ellipsoid or Eigelenk ( articulatio ellipsoidea ): biaxial, for example, the first head joint between the atlas and skull; wrist joint between the radius and carpal bones; allows for both flexion-extension movement as well as side-to - Since movement.
• Saddle joint ( articulatio sellaris ): biaxial, for example, the joint between the carpal bones and metacarpal bone below the thumb; can be moved around two axes: flexion and extension, abduction and adduction
• Hinge joint ( ginglymus ): uniaxial, can only bend (flexion ) and stretch (extension), for example, the elbow joint ( between humerus and ulna ); the finger joints with the exception of the metacarpophalangeal joints.
• Roll, wheel or pivot joint ( articulatio trochoidea ): uniaxial, for example, radio-ulnar joint ( between the radius and ulna ) and atlantoaxial
• A planar joint or swivel joint ( articulatio plana ): no geometrical center of motion, also called joint plan, for example, between spinous processes. Special feature: two translational degrees of freedom.
• Bicondyläres joint or Kondylengelenk ( articulatio bicondylaris ): knee joint, biaxial, connecting two condyles with different curvatures: flexion - extension, external and internal rotation (only with the knee flexed possible).
• Tight joint ( amphiarthrosis ): for example, sacroiliac joint

Joint cracking

The cause of the " popping " of joints (for example, finger clicking) is not yet fully understood. The most common explanation is gas bubbles in the synovial fluid that cause blistering at a pressure equalizing noise, called ( cavitation). Also irregularities in the surface of the ankle are conceivable as a possible cause.

Habitual Cracking joints is considered by experts as not very harmful. It can not cause arthritis, but may reduce the gripping force.

Movements in the joints

To describe and represent excursions joint, is in the anatomy and the physical concept of degrees of freedom use, by which the position of two bodies a coordinate system is defined in the space to each other and corresponding to the translated as " main direction ". However, this is misleading because yes to each movement, the antagonistic movement belongs ( eg internal and external rotation ), the directions are opposite, but the plane in which the movements are represented, is exactly one, and this is the degree of freedom. The degree of freedom is perpendicular to the axis of movement.

The ranges of motion of joints are measured in orthopedics using the neutral zero method. The ranges of motion of a normal position ( " neutral " or " zero " ) are determined on the basis in both directions. The normal position is the attitude of taking the joints when standing upright with arms hanging down and closed feet. In this position, for example, by stretching the knee, and the foot is at right angles to the tibia. The ranges of motion are now measured in both directions, that is, in the example of foot dorsiflexion and plantar flexion of the scope is determined. The values ​​determined are listed in order. The value for flexion is usually listed first, followed by the neutral position comes in the form of a zero, and finally the range of motion for extension is called. In the example of the foot, therefore, could be 30 ° - 0 ° - 40 ° monitor.

If the full range of motion is not given by a contracture and is thereby not reaching the neutral position only, as is the 0 and the failure to achieve value of the failure to exercise the passage at the beginning or end, depending on which value for the extension or flexion passage through prevented zero. In a hip with a flexion contracture of 20 ° ( a stretch of 20 ° corresponds to maximum ) could be the quotation, for example, are as follows: 130 ° - 20 ° - 0 °. Since the maximum aspect ratio is from 20 ° to prevent the passage through the neutral point, zero is behind, that is not in the figures.

Orthoses the ranges of motion are also listed according to the neutral -0- method. If, for example, in a knee brace the full extension and flexion of the leg be avoided due to ligament injuries, the quotation is often 60-10 - 0 The knee can be stretched in this setting to a maximum of 10 ° and not more than 60 ° flexed.

Names for movements

For the different movements of individual body parts, there are names, of which some are listed here:

• Abduction
• Adduction
• External rotation
• Dorsiflexion
• Extension
• Inflection
• Dip
• Internal rotation
• Lateral flexion
• Nutation
• Opposition
• Palmar flexion
• Plantar flexion
• Reclination
• Reduction
• Pronation
• Supination