Abstract: Twenty-six patients with Legg-perthes’disease were studied （23 males,3 females）. The patients’age ranged from 6-11 years. Based on Catterall’s grouping,these patients consist of group Ⅰ,2 cases;group Ⅱ, 10 cases;group Ⅲ,14 cases. Five normal hips were measured,which intra-articular pressure showed nagtive pressure. The changes of intra-capsule pressure seen in Legg-perthes’disease were noted as: （1）.Ⅰ.Ⅱ groups with increasing pressure.（2）.Ⅲ group with nagtive pressure.These findings suggest that this condition is probably due to synovitis of the hip joint.The increased pressure of intra-capsule might be a disturbance of venous return in the proximal femur.