How fast can legg-calve-perthes disease symptoms show up? is it a really slow disease?

Slow disease: Children younger than 6 have the best prognosis since they have time for the dead bone to revascularize and remodel, with a good chance that the femoral head will recover and remain spherical after resolution of the disease. [12] children who have been diagnosed with perthes' disease after the age of 10 are at a very high risk of developing coxa magna.

Varies: First symptom is often limping, which is usually painless. Sometimes there may be mild pain that comes and goes. knee pain,worsening pain and limping as time goes by thigh or groin when putting weight on the affected leg or moving the hip joint, onstant thigh pain,reduced joint motion, joint stiffness,thigh muscles (atrophy)