Growth disturbance in Legg-Calve-Perthes disease and the consequences of surgical treatment. Seventy-two patients with Legg-Calve-Perthes disease were studied to assess the interference with proximal femoral growth as a result of the disease itself and of surgical treatment. Twenty-five patients were treated nonoperatively, 20 were treated by femoral varus derotation osteotomy, and 27 by innominate osteotomy. All patients were studied clinically for evidence of abductor weakness and leg-length discrepancy. They were also studied roentgenographically for evidence of femoral head deformity and trochanteric overgrowth. The overall results showed a 6% incidence of leg-length discrepancy greater than 2 cm after both operative and nonoperative treatment. The articulo-trochanteric distance (ATD) was less than +5 mm in 23% of patients, of which 43% had a positive Trendelenburg sign. A significantly lower mean ATD was found in patients treated by femoral varus osteotomy, which should be avoided in patients over eight years of age. The study also demonstrated a strong association between coxa magna and growth disturbance of the proximal femoral physis manifesting itself as either a leg-length discrepancy or as a low ATD. The significant effects of growth disturbance after treatment must be considered, as well as the sphericity of the healed femoral head, in the final assessment in Legg-Calve-Perthes disease. 