A 68-year-old woman presents with rheumatoid arthritis. What deformity is most likely to occur at her metacarpophalangeal joints?

In rheumatoid arthritis, especially as it progresses, the metacarpophalangeal joints (MCP) are particularly affected due to the inflammatory nature of the disease. As the condition deteriorates, the forces at play around these joints tend to lead to specific deformities as a result of the disease's chronic impact on the joint structures.

Volar subluxation and ulnar deviation arise at the MCP joints due to the imbalance between the flexor and extensor tendons. With the involvement of erosive changes in the joints and soft tissue inflammation, there's a tendency for the fingers to deviate ulnarly as the joints become lax and distorted. Additionally, the volar subluxation occurs because the palmar ligaments and capsule are often compromised in rheumatoid arthritis, allowing the proximal phalanx to displace volarly. This results in a characteristic appearance where the fingers point towards the ulnar side of the hand while the proximal phalanx is shifted forward.

The other options present various deformities but are not as characteristic of the changes seen at the MCP joints specifically in rheumatoid arthritis. Radial deviation and dorsal subluxation imply a different pathology or positioning of the fingers, which is less common in this condition. Similarly