What describes the movement of the convex bone on a concave surface?

In the context of joint mechanics, when a convex bone surface moves on a concave surface, the movement occurs in a manner that is opposite to the direction of the desired motion. This principle is derived from the convex-concave rule, which states that for joints where one surface is convex and the other is concave, the convex surface will glide in a direction that is opposite to the movement of the limb or the distal bone segment.

For instance, if you consider an action where the arm is being raised (the distal segment moving upward), the convex surface of the humeral head moves downward and posteriorly on the concave glenoid cavity of the scapula. This relationship is fundamental in understanding joint mobilization techniques and is crucial for athletic trainers and rehabilitation professionals when assessing and treating joint problems.