Concave-Convex Rule in Joint Movement

Joint Movement

• When the body segment moves upward, the convex joint surface moves downward.
• The cupped right hand in the joint demonstration represents the concave joint surface.
• When raising the left elbow, the cupped right hand moves downward in relation to the left fist.
• When the left forearm moves up during the joint demonstration, the left fist moves upward.
• A concave joint surface will move in the opposite direction as the moving body segment on a fixed convex surface.
• During finger extension, the concave joint surface of the phalanx moves in the same direction as the phalanx itself while moving on the convex metacarpal joint surface.
• A concave joint surface moves on a fixed convex surface in the same direction the body segment is moving.
• The bone end shape that requires joint surfaces to move in a specific way during joint movement is the convex-concave joint surface.
• During shoulder flexion, the convex joint surface moves upward on a fixed concave surface.
• The bone end shape determines how joint surfaces need to move during joint movement.

Test your knowledge about the concave-convex rule, which describes how the differences in shapes of bone ends require joint surfaces to move in a specific way during joint movement. Understand how a concave joint surface moves on a fixed convex surface in the same direction as the body segment.