ObjectiveTo investigate the effectiveness of internal and external lysis combined with Ilizarov external fixation technology for severe knee pathological flexion contracture deformity in children.MethodsA retrospective analysis was made on 12 children (12 knees) with severe knee pathological flexion contracture deformity who were treated with internal and external lysis and Ilizarov external fixation between August 2012 and January 2017. There were 9 boys and 3 girls with an age of 3-12 years (mean, 8.4 years). There were 8 cases of tuberculosis, 3 cases of haemophilia A, and 1 case of residual deformity after extensive hemangioma drug injection. The disease duration ranged from 5 months to 4 years, with an average of 20.3 months. The degree of knee contracture was (67.42±23.30)°, and the range of motion of knee was (38.33±14.98)°. The preoperative Western Ontario and McMaster University Osteoarthritis Index (WOMAC) score was 78.42±15.57. The complication was observed after operation, and the degree of knee contracture, range of motion, and WOMAC score at 3 months and 1 year after operation were recorded and compared with those before operation.ResultsThe operations completed successfully in all children. All the 12 cases were followed up 9-24 months (mean, 14.5 months). All incisions healed by first intention after operation. The knee function of all children improved significantly and the weight-bearing walking function of the lower limbs restored. The degree of knee contracture, range of motion, and WOMAC score were significantly improved at 3 months and 1 year after operation (P<0.05), but there was no significant difference between 3 months and 1 year after operation (P>0.05).ConclusionFor severe knee pathological flexion contracture deformity in children, application of internal and external lysis combined with Ilizarov external fixation has advantages, such as small trauma, rapid recovery, and early postoperative knee function training, and good effectiveness.