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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 joint space equals the distance between the involved bones of the joint. A joint space narrowing is a sign of either (or both) osteoarthritis and inflammatory degeneration. [12] The normal joint space is at least 2 mm in the hip (at the superior acetabulum), [13] at least 3 mm in the knee, [14] and 4–5 mm in the shoulder joint. [15]
Histology of a synovial membrane. H&E stain. The synovial membrane is variable but often has two layers: [4] The outer layer, or subintima, can be of almost any type of connective tissue – fibrous (dense collagenous type), adipose (fatty; e.g. in intra-articular fat pads) or areolar (loose collagenous type).
The joint allows inversion and eversion of the foot, but plays minimal role in dorsiflexion or plantarflexion of the foot. [5] The centre of rotation of the subtalar joint is thought to be in the region of the middle facet. [3] It is considered a plane synovial joint, also commonly referred to as a gliding joint. [6]
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.
The acromioclavicular joint provides the ability to raise the arm above the head. This joint functions as a pivot point (although technically it is a gliding synovial joint), acting like a strut to help with movement of the scapula resulting in a greater degree of arm rotation.
The inner layer is mainly composed of two cell types, specialized macrophages (macrophage-like synovial cells) and fibroblast-like synoviocytes, which are important in maintaining the internal joint homeostasis. These cells represent the main source of hyaluronic acid and also other glycoproteins, major components of the synovial fluid. [1] [2]
Cells at the center of this interzone region undergo cell death to form the joint cavity, while surrounding mesenchyme cells will form the articular capsule and supporting ligaments. The process of endochondral ossification, which converts the cartilage models into bone, begins by the twelfth week of embryonic development.