Joints, or articulations, are points where two or more bones connect, allowing the skeletal system to function as a movable structure. They are classified based on the degree of movement they permit. The gliding joint is a specialized articulation that coordinates subtle movements throughout the body and is structurally classified as a plane joint.
Structure and Classification
Gliding joints belong to the group of freely movable articulations known as synovial joints. They are defined by their articulating surfaces, which are flat or only slightly curved. This planar structure is the reason for their alternate name, plane joints.
Like all synovial joints, the gliding joint is enclosed by a fibrous joint capsule that maintains the integrity of the articulation. The ends of the bones within this capsule are covered with a layer of hyaline cartilage, which reduces friction as the surfaces interact. Synovial fluid fills the joint cavity, providing lubrication and minimizing wear between the bone ends.
Range of Motion
The movement allowed by a gliding joint is characterized by a simple sliding or slipping of one bone surface over another. This mechanical action is known as translation, where the bones move in the same plane but do not revolve around a central axis. Because the joint does not have a single axis of rotation, it is functionally classified as non-axial.
Although the motion at any single gliding joint is small, it allows movement along two axes, meaning the joint can be considered multiaxial. The movement is limited by the tight joint capsule and the surrounding ligaments that hold the bones securely together. This configuration permits side-to-side and back-and-forth movement, but it prevents significant rotation or angular motion.
Primary Anatomical Locations
Gliding joints are positioned in areas of the body that require flexibility through small, coordinated movements rather than large ranges of motion. A primary example is the wrist, where the intercarpal joints allow the carpal bones to slide against one another. This collective sliding motion provides the wrist with the flexibility to adjust the hand’s grip and position.
Foot and Shoulder
A similar arrangement exists in the foot at the intertarsal joints, where the tarsal bones articulate to provide flexibility and shock absorption during walking and running. The slight gliding motion between these bones helps the foot conform to uneven surfaces.
In the shoulder region, the acromioclavicular joint connects the clavicle (collarbone) to the acromion of the scapula (shoulder blade). This joint allows the scapula to move slightly relative to the clavicle, which is necessary for elevating the arm above the head.
Gliding joints are also found in the axial skeleton, specifically as the facet joints between the vertebrae of the spine. These joints allow for slight adjustments between adjacent vertebrae, enabling the vertebral column to bend and twist while maintaining stability and supporting body weight.