Common symptoms include hip, knee (hip pathology can refer pain to a normal knee), or
groin pain, exacerbated by hip/leg movement, especially internal hip rotation (twisting the leg toward the center of the body). There is reduced range of motion, particularly in abduction and
internal rotation, and the patient presents with a limp. Pain is usually mild. There may be atrophy of thigh muscles from disuse and an inequality of leg length. In some cases, some activity can
cause severe irritation or inflammation of the damaged area including standing, walking, running, kneeling, or stooping repeatedly for an extended period of time. In cases exhibiting severe femoral
osteonecrosis, pain is usually a chronic, throbbing sensation exacerbated by activity.
The first signs are complaints of soreness from the child, which are often dismissed
as growing pains, and limping or other
guarding of the joint, particularly when tired. The pain is usually in the hip, but can also be felt in the knee ('referred pain'). In some cases, pain is felt in the unaffected hip and leg, due to the child favoring the
injured side and placing the majority of their weight on the "good" leg. It is predominantly a disease of boys (4:1 ratio). Perthes is generally diagnosed between 5 and 12 years of age, although it
has been diagnosed as early as 18 months. Typically the disease is only seen in one hip, but bilateral Perthes is seen in about 10% of children diagnosed. (The differential diagnosis for bilateral
Perthes disease is Multiple Epiphyseal Dysplasia).