Which finding best distinguishes a joint effusion from an intra-articular injury?

• A. Joint effusion presents as diffuse swelling and tenderness.
• B. Joint locking or catching is typical of a fracture.
• C. Intra-articular injury may present with joint locking, catching, or reduced ROM.
• D. Joint swelling is not seen with intra-articular injuries.

Answer: (C)

Mechanical symptoms within the joint—like locking or catching—signal a problem inside the joint itself. An intra-articular injury often disrupts structures such as the meniscus or articular surfaces, leading to these catching or locking episodes and sometimes a reduced range of motion as the joint can’t move smoothly. In contrast, a joint effusion is excess fluid in the joint that causes diffuse swelling and tenderness but doesn’t by itself create mechanical obstruction. So the best clue pointing to an intra-articular injury is the presence of locking, catching, or reduced ROM. Swelling can occur with both conditions, but the absence of mechanical symptoms would make a pure effusion more likely; locking is not typical of a fracture, and swelling is indeed seen with some intra-articular injuries.