What are some strategies for radiographically differentiating between erosions secondary to erosive osteoarthritis versus psoriatic arthritis involving the DIP joints?

In erosive OA, DIP changes show central (or paracentral) erosions with gull-wing appearance. Gull-wing appearance is created by the sclerotic border of erosion in OA (sclerotic border is typically not present in PsA). In addition, at least DIPs are involved in OA (Ridley et al., PMID 30309145).

In PsA, erosions are more peripheral with adjacent periostitis and/or proliferative changes around the affected joint (giving it a fuzzy appearance). One may also see pencil-in-cup deformity in an adjacent digit (additional clue). Sudol-Szopinska et al., PMID 27104004

The final diagnosis is always clinical but one may need more advanced imaging, such as- MRI.