American Board of Family Medicine (ABFM) Practice Exam 2026 - Free ABFM Practice Questions and Study Guide

The condition characterized by insidious onset of pain and mild limitation of range of motion in one hip joint in a 2-12 year old boy is idiopathic osteonecrosis of the hip, also known as Perthes disease. This condition typically presents with gradual onset of hip or groin pain, which may be accompanied by referred pain to the knee. The limited range of motion is often noted upon examination, particularly in terms of internal rotation and abduction of the hip.

Idiopathic osteonecrosis occurs when the blood supply to the femoral head is temporarily disrupted, leading to avascular necrosis of the bone. This condition most commonly affects boys between the ages of 4 and 10, although it can present in children as old as 12, making the age group relevant for this scenario.

Other options listed exhibit different characteristics: slipped capital femoral epiphysis usually presents with more acute hip or knee pain, altered gait, and a history of obesity or hormonal changes, often involving children just prior to or during adolescence. Osteochondritis dissecans can also involve joint pain and can affect those active in sports, but it primarily shows a more active pain pattern and can involve locking of the joint. Septic arthritis would typically present with