Pencil-in-cup deformity

Last revised by Evangeline Collins on 30 Aug 2024

Pencil-in-cup deformity is the description given to one of the appearances on plain radiographs classically associated with psoriatic arthritis; however, it is not pathognomonic.

Radiographic features

The appearance results from periarticular erosions and bone resorption giving the appearance of a pencil in a cup.

Differential diagnosis

Although classically described with psoriatic arthritis, this appearance can also be seen in:

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