LCP (Lego-Calve-Perthes) disease almost always results with various degrees of deformity in proximal femur. Several intra- and extraarticular deformities such as coxa magna, coxa plana, coxa breva, loss of sphericity, joint incongruency, instability, trochanteric overgrowth, shortening, and acetabular dysplasia may diminish joint congruency and biomechanics which precipitate osteoarthritis. Prognostic factors are age, size and location of epiphyseal involvement, and size of the ossific nucleus. In Perthes sequela, prevalance of radiological osteoarthritis is higher than normal population. In addition, progression of osteoarthritis accelerates after fourth decade in patients with LCP disease.