Question

question 19 (mandatory) (2 points)
which of the following occurs during pronation at the distal radioulnar joint?
a) the convex radius rolls posterior and glides anterior
b) the concave radius rolls and glides posterior
c) the concave radius rolls and glides anterior
d) the convex radius rolls anterior and glides posterior

Explanation:

To solve this, we recall the kinematics of the distal radioulnar joint during pronation. The radius is convex at the distal radioulnar joint. During pronation, the convex radius rolls anteriorly and glides posteriorly (using the convex - concave rule: for a convex surface moving on a concave surface, the roll and glide directions are opposite). Let's analyze each option:

• Option a: Incorrect direction of roll and glide.
• Option b: The radius is convex, not concave, so this is wrong.
• Option c: The radius is convex, not concave, so this is wrong.
• Option d: Matches the kinematics of the convex radius during pronation (rolls anterior, glides posterior).

Answer:

d) The convex radius rolls anterior and glides posterior