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A joint or articulation (or articular surface) is the connection made between bones, ossicles, or other hard structures in the body which link an animal's skeletal system into a functional whole. [ 1 ] [ 2 ] [ 3 ] They are constructed to allow for different degrees and types of movement.
A multiaxial joint, such as the hip joint, allows for three types of movement: anterior-posterior, medial-lateral, and rotational. A multiaxial joint (polyaxial joint or triaxial joint) is a synovial joint that allows for several directions of movement. [9] In the human body, the shoulder and hip joints are multiaxial joints. [10]
A plane joint (arthrodial joint, gliding joint, plane articulation) is a synovial joint which, under physiological conditions, allows only gliding movement. Plane joints permit sliding movements in the plane of articular surfaces. The opposed surfaces of the bones are flat or almost flat, with movement limited by their tight joint capsules.
The shoulder joint involves articulation between the glenoid cavity of the scapula (shoulder blade) and the head of the upper arm bone and functions as a diarthrosis and multiaxial joint. Due to the very loose joint capsule that gives a limited interface of the humerus and scapula, it is the most mobile joint of the human body.
The presence of an articular disk also permits a more even distribution of forces between the articulating surfaces of bones, increases the stability of the joint, and aids in directing the flow of synovial fluid to areas of the articular cartilage that experience the most friction. The term "meniscus" has a very similar meaning. [1]
The knee joints and ankle joints are less typical, as they allow a slight degree of rotation or side-to-side movement in certain positions of the limb. The knee is the largest hinge joint in the human body. Hinge and pivot joints are both types of synovial joint. A hinge joint can be considered a modified sellar/saddle joint, with reduced ...
On the trunk of the body, the chest is referred to as the thoracic area. The shoulder in general is the acromial, while the curve of the shoulder is the deltoid. The back as a general area is the dorsum or dorsal area, and the lower back as the lumbus or lumbar region.
The ball-and-socket joint (or spheroid joint) is a type of synovial joint in which the ball-shaped surface of one rounded bone fits into the cup-like depression of another bone. The distal bone is capable of motion around an indefinite number of axes, which have one common center. This enables the joint to move in many directions.