While there are more than five types of joints in the human body, a common classification focuses on the synovial joints, which are freely movable. Five common types of synovial joints are frequently cited:
Five Key Synovial Joint Types
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Hinge Joints: These joints allow movement in only one plane, like a door hinge. Examples include the elbow and knee joints. The articulation occurs between the convex end of one bone and the concave edge of another.
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Saddle Joints: These joints allow movement in two planes (flexion/extension and abduction/adduction), but not rotation. The carpometacarpal joint of the thumb is a prime example.
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Planar Joints: Also known as gliding joints, these allow for short, gliding movements. They are found between the carpal bones (wrist) and tarsal bones (ankle).
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Pivot Joints: These joints allow for rotation around a single axis. The joint between the first and second vertebrae in the neck (atlantoaxial joint) is a classic pivot joint enabling head rotation.
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Ball-and-socket Joints: These joints allow for movement in all three planes (flexion/extension, abduction/adduction, and rotation). The shoulder and hip joints are the primary examples.
Numerous sources detail various classifications of joints, including fibrous, cartilaginous, and synovial types. However, focusing on the freely movable synovial joints, the above five represent a common and readily understandable categorization. Other classifications may include condyloid joints, but for the sake of simplicity, these five are a clear and concise answer to the question.
