In Neer's classification for impingement-related lesions, Type III acromion is described as which morphology?

• A. Hooked at the edge
• B. Flat
• C. Curved
• D. Convex

Answer: (A)

Neer’s impingement classification uses the shape of the acromion to explain how the subacromial space is affected during arm elevation. Type III is described as a hooked, beak-like inferior projection of the acromion, meaning the edge angles downward and projects into the subacromial space. This hooked morphology narrows the space under the acromion and increases contact with the rotator cuff tendons and bursa during elevation, leading to impingement. That downward-hooked edge best captures the characteristic appearance of this type, making “hooked at the edge” the correct description. Flat and curved describe the other types, and convex isn’t part of Neer’s terminology.