A patient presents with a painful, translucent, fluid-filled mass on the dorsal aspect of the distal interphalangeal (DIP) joint. This ‘mucous cyst’ is pathogenically and clinically most strongly associated with which underlying condition?

Explanation:
The correct option is a. A digital mucous cyst is essentially a ganglion cyst that arises from the DIP joint capsule. It is intimately and almost universally associated with underlying DIP joint osteoarthritis and the formation of marginal osteophytes (Heberden's nodes). The osteophyte causes capsular irritation and fluid leakage, forming the cyst stalk. If surgical excision is performed, the underlying osteophyte must be thoroughly debrided to prevent an almost certain recurrence of the cyst. Reference: Brown RE, Zook EG. Russell RC. Fingernail deformities secondary to ganglions of the distal interphalangeal joint (mucous cysts). Plast Reconstr Surg.