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In geology, a brittle fracture surface in rocks along which little or no displacement has occurred.
Present in nearly all surface rocks, joints extend in various directions, generally more vertical than horizontal. Joints may have smooth, clean surfaces, or they may be scarred by slickensides, or striations. Jointing does not extend very far into the Earth's crust, because at about 7.5 mi (12 km) even rigid rocks tend to flow plastically in response to stress.
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Structure connecting two or more
Most joints, including synovial (fluid-containing) joints and those between vertebrae, which incorporate a disk, can move. Immovable joints include the sutures of the skull (see fontanel ). Ligaments connect the bones of a joint, but muscles keep them in place. Joint disorders include various forms of arthritis , injuries (e.g., sprains, fractures , and dislocations ), congenital disorders , and vitamin deficiencies.
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[c mediumvioletred] (as used in expressions)
Joint Photographic Experts Group
degenerative joint disease
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