Which radiographic finding is characteristic of Sinding-Larsen-Johansson syndrome?

Sinding-Larsen-Johansson syndrome is characterized by pain and tenderness at the inferior pole of the patella, which is associated with traction apophysitis, often seen in active adolescents. The condition arises due to repetitive stress and leads to inflammation and possibly microtrauma at the patellar tendon insertion.

The splintering of the inferior pole of the patella, the correct answer, reflects the typical radiographic changes that can be observed in patients with this syndrome. Although it may not always be present on imaging, when it does occur, it indicates the stress and strain on the area where the patellar tendon attaches to the patella, illustrating the pathology underlying this condition.

Other options describe conditions that are not related to Sinding-Larsen-Johansson syndrome. For instance, a fracture of the patella pertains to acute injuries rather than chronic traction injuries, while knee joint dislocation and joint effusion in the femur generally involve entirely different mechanisms and pathologies, further distinguishing them from the chronic stress injuries seen in Sinding-Larsen-Johansson syndrome.