In Neer's classification for impingement syndrome, Type II acromion is described as which characteristic?

• A. Flat-shaped acromion
• B. Curved acromion parallel to the humeral head
• C. Hooked acromion
• D. Irregular acromion

Answer: (B)

In Neer's impingement classification, the acromion is described by how its inferior surface sits relative to the humeral head. Type II is the curved acromion, with its inferior surface forming a gentle arc that runs parallel to the humeral head. This curvature narrows the subacromial space as the arm is raised, promoting impingement of the rotator cuff tendons and subacromial tissues.

This differs from a flat acromion, which has no downward curvature and thus typically causes less impingement, and from a hooked acromion, which projects more inferiorly and can cause greater mechanical compression. An irregular acromion is not part of Neer’s original categories. Therefore, the curved shape parallel to the humeral head best fits Type II.