A joint is the location at which two bones make contact. Joints are constructed to both allow movement and provide mechanical support. Grays illustration of a human femur, a typically recognized bone. ...

Classification

Structure and function of a joint are closely related.

Structural classification

Structurally, joints are classified as:

• fibrous - bones are connected by fibrous connective tissue.
• cartilaginous - bones are connected by cartilage.
• synovial - there is a space (synovial cavity) between the articulating bones.

Connective tissue is any type of biological tissue with an extensive extracellular matrix and often serves to support, bind together, and protect organs. ... Cartilage is a type of dense connective tissue. ... Synovial fluid is a thick, stringy fluid found in the cavities of synovial joints. ...

Fibrous joints

In fibrous joints bones are joined by tight and inflexible layers of dense connective tissue, consisting mainly of collagen fibers. In adults, these are not designed to allow any movement; however, in children, fibrous joints have not solidified and are movable. Examples of fibrous joints are: In zootomy, fibrous connective tissue (FCT) is a type of connective tissue which has relatively high tensile strength, due to a relatively high concentration of collagenous fibers. ... Collagen triple helix. ... The term adult describes any mature organism, but normally it refers to a human: one that is no longer a child / minor and is now either a man or a woman. ... A male Caucasian toddler child A child (plural: children) is a young human. ...

• Cranial sutures, joining the bones of the cranium.
• Gomphoses, the joints between the roots of the teeth and their sockets (or alveoli) in maxilla and mandible.

A hippopotamuss skull A skull, or cranium, is a bony structure of Craniates which serves as the general framework for a head. ... Types of teeth Molars are used for grinding up foods Carnassials are used for slicing food. ... The maxillae are the largest bones of the face, except for the mandible, and form, by their union, the whole of the upper jaw. ... The mandible (inferior maxillary bone) (together with the maxilla) is the largest and strongest bone of the face. ...

Cartilaginous joints

In cartilaginous joints (also known as synchondroses) bones are connected entirely by cartilage. In comparison to synovial joints, cartilaginous joints allow only slight movement. Examples of cartilaginous joints are the pubic symphysis, the joints between the ribs and the sternum, and the cartilage connecting the growth regions of immature long bones. The pubic symphysis is the midline cartilaginous joint uniting the superior rami of the left and right pubic bones (pubis). ... The human rib cage. ... Sternum or breastbone is a long, flat bone located in the center of the thorax (chest). ... Grays illustration of a human femur, a typically recognized bone. ...

Synovial joints

The term "Synovial joint" and "Diarthrosis joint" are often used interchangably, although the first term refers to the structure and the second one to the function. For more details, see "Diarthrosis joints" below.

Functional classification

Functionally, they can be classified as:

• synarthrosis - permit no movement.
• amphiarthrosis - permit little movement.
• diarthrosis - permit a variety of movements (e.g. flexion, adduction, pronation). Only synovial joints are diarthrosis.

In anatomy, Flexion is movement whereby bones or other objects are brought closer together. ... In anatomy and physiology, adduction is the moving of limbs towards the midline of the body. ... In human and zoological anatomy (sometimes called zootomy), several terms are used to describe the location of organs and other structures in the body of bilateral animals. ...

Synarthrosis joints

Synarthroses are joints with very little (if any) mobility. They can be categorised by how the two bones are joined together:

• Syndesmoses are joints where the two bones are joined by one of more ligaments.
• Synchondroses are joints where the two bones are joined by a piece of cartilage.
• Synostoses are the fusion of two bones, to the point that they are practically one bone. In humans, the plates of the cranium, initially separate, fuse together as the 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.
• Amphiarthroses are slightly moveable joints where the two bone surfaces at the joint - both covered in hyaline cartilage - are joined by strands of fibrocartilage.

Craniostenoses are a group of cephalic disorders in which the plates of the cranium in children fuse prematurely, resulting in deformities of the skull. ... Cartilage is type of dense connective tissue. ...

Amphiarthrosis joints

Most amphiarthrosis joints are cartilaginous. See above for more details.

Diarthrosis joints

Joints:
1-ball & socket; 2-ellipsoid; 3-saddle; 4-hinge; 5-pivot;

Diarthroses (sometimes called synovial joints and also diarthroidal joints) are the most common and most moveable type of joint in the body. Image File history File links Download high resolution version (1500x1000, 357 KB) Beschreibung: Gelenke Quelle: [1] Zeichner: Produnis Legende: Kugelgelenk Eigelenk Sattelgelenk Scharniergelenk Zapfengelenk Lizenzstatus: File links The following pages link to this file: Joint ... Image File history File links Download high resolution version (1500x1000, 357 KB) Beschreibung: Gelenke Quelle: [1] Zeichner: Produnis Legende: Kugelgelenk Eigelenk Sattelgelenk Scharniergelenk Zapfengelenk Lizenzstatus: File links The following pages link to this file: Joint ...

The whole of a diarthrosis is contained by a ligamentous sac called the articluar capsule.

The surfaces of the two bones at the joint are covered in cartilage. The thickness of the cartilage varies with each joint, and sometimes may be of uneven thickness. Articular cartilage is multi-layered. A thin superficial layer provides a smooth surface for the two bones to slide against each other. Of all the layers, it has the highest concentration of collagen and the lowest concentration of proteoglycans, making it very resistant to shear stresses. Deeper than that is an intermediate layer, which is mechanically designed to absorb shocks and distribute the load efficiently. The deepest layer is highly calcified, and anchors the articular cartilage to the bone. Cartilage is a type of dense connective tissue. ... Collagen triple helix. ... Proteoglycans represent a special class of glycoprotein that are heavily glycosylated. ...

In joints where the two surfaces do not fit snugly together, a meniscus or multiple folds of fibro-cartilage within the joint correct the fit, ensuring stability and the optimal distribution of load forces.

The synovium is a membrane that covers all the non-cartilaginous surfaces within the articular capsule. It secretes synovial fluid into the joint, which nourishes and lubricates the articular cartilage. The synovium is separated from the capsule by a layer of celluar tissue that contains blood vessels and nerves. Synovium means with egg, because the (synovial) fluid in joints that have a cavity between the bearing surfaces is like egg-white. ... Synovial fluid is a thick, stringy fluid found in the cavities of synovial joints. ...

Synovial joints can be further grouped by their shape, which controls the movement they allow:

• Gliding joints, such as in the carpals of the wrist. These joints allow a wide variety of movement, but not much distance.
• Hinge joints, such as the elbow (between the humerus and the ulna). These joints act like a door hinge, allowing flexion and extension in just one plane.
• Pivot joints, such as the elbow (between the radius and the ulna). This is where one bone rotates about another.
• Condyloid (ellipsoid) joints, such as the knee. When the knee is extended there is no rotation, when it is flexed some rotation is possible. A condyloid joint is where two bones fit together with an odd shape (e.g. an ellipse), and one bone is concave, the other convex. Some classifications make a distinction between condyloid and ellipsoid joints.
• Saddle joints, such as at the thumb (between the metacarpal and carpal). Saddle joints, which resemble a saddle, permit the same movements as the condyloid joints.
• Ball and socket joints, such as the hip joint. These allow a wide arrange of movement.

In human anatomy, the carpal bones are the bones of the human wrist. ... Elbow redirects here. ... The humerus is a long bone in the arm or fore-legs (animals) that runs from the shoulder to the elbow. ... The ulna (along with the radius) is one of the two bones in the forearm. ... The front door of a house is often decorated to appear inviting. ... A hinge is a mechanical device that connects two solid objects, allowing rotation between them. ... Elbow redirects here. ... The radius and ulna of the left forearm, posterior surface. ... The ulna (along with the radius) is one of the two bones in the forearm. ... An x-ray of a human knee In human anatomy, the knee is the leg joint connecting the femur and the tibia. ... In mathematics, an ellipse (from the Greek for absence) is a plane algebraic curve where the sum of the distances from any point on the curve to two fixed points is constant. ... The thumbs up gesture is a sign of approval in many cultures. ... The metacarpus is the intermediate part of the hand skeleton that is located between the fingers distally and the carpus which forms the connection to the forearm. ... In human anatomy, the carpal bones are the bones of the human wrist. ... Tack is any of the various accessories worn by horses in the course of their use as domesticated animals. ... Bones of the Hip In anatomy, the hip is the bony projection of the femur, known as the greater trochanter, and the overlying muscle and fat. ...

See also

• Arthrology, the science concerned with the anatomy, function, dysfunction and treatment of joints.
• Kinesiology, the study of musculoskeletal movements.
• condyloprotector
• arthritis
• Replacement joint

Kinesiology is the study of human movement. ... Arthritis (from Greek arthro-, joint + -itis, inflammation) is a group of conditions that affect the health of the bone joints in the body. ... Joint Replacement is one of the commonest and most successful operations in modern orthopaedic surgery. ...

External links

• Illustration of synovial joints