Which condition is likely if there is high fever and swelling of the affected joint?

Septic arthritis is characterized by the presence of infection in a joint, which leads to pronounced symptoms such as high fever and swelling of the affected joint. This condition often occurs when bacteria, viruses, or fungi enter the joint space, usually through the bloodstream or direct infection. The inflammation caused by the infection results in significant pain, swelling, and loss of mobility in the joint, accompanied by a systemic response that often manifests as fever. Early diagnosis and treatment are crucial to prevent joint damage.

The other conditions listed do not typically present with both high fever and significant joint swelling. Osgood-Schlatter disease primarily affects adolescents and is related to activity-induced knee pain rather than infection. Legg-Calve-Perthes disease is a childhood hip disorder resulting from the loss of blood supply to the femoral head and does not commonly cause fever or swelling indicative of infection. Slipped capital femoral epiphysis involves slippage of the femoral head and can lead to hip pain but similarly does not usually include fever or signs of infection. Hence, the presence of fever and joint swelling points strongly towards septic arthritis.