Which feature is characteristic of osteoarthritis (OA) on an X-ray?

Osteoarthritis (OA) is primarily characterized by degenerative changes in the joints, which are reflected in specific findings on X-rays. The presence of subchondral bone cysts is a notable feature associated with OA. These cysts occur beneath the cartilage surface where the bone becomes injured or remodels due to the degeneration of cartilage and can be seen on imaging studies.

In OA, the joint cartilage wears away, leading to increased pressure and stress on the underlying bone, promoting the formation of these cysts as a response to the changes in the joint dynamics.

The other options do not represent the classic X-ray findings associated with osteoarthritis. Juxta-articular bony erosions are more characteristic of inflammatory arthritides, such as rheumatoid arthritis, rather than the wear-and-tear nature of OA. Similarly, periarticular soft tissue swelling may indicate inflammation or fluid accumulation but is not a defining X-ray feature of OA itself. Fatigue and weight loss are systemic symptoms that could occur in a variety of conditions but are not indicative of osteoarthritis as visualized on an X-ray. Therefore, the identification of subchondral bone cysts is a hallmark feature of osteoarthritis on radiographic examinations.