Which of the following conditions has an insidious onset rather than an acute onset of limp?

Legg-Calve-Perthes disease is characterized by an insidious onset of limping rather than an abrupt or acute onset. This condition involves avascular necrosis of the femoral head, which develops over time as blood supply to the area diminishes, leading to gradual symptoms. Patients often experience a progressive limp without a specific traumatic event that triggers the onset, making the symptoms gradually manifest.

In contrast, conditions like Osgood-Schlatter disease typically arise from repetitive stress and impact to the knee, often seen in young athletes, leading to more immediate pain and limping. Septic arthritis usually presents with sudden onset of severe pain, swelling, and fever, indicating an infection that develops rapidly. Slipped capital femoral epiphysis can also have an acute presentation, particularly if it involves a sudden slip.

Understanding the nature of the onset for these conditions is crucial for proper diagnosis and management in clinical practice.