We report a very rare injury of a 8-year-old girl with sacroiliac fracture dislocation and triradiate cartilage separation. After the restoration of the sacroiliac joint by open means, reduction of the separated cartilage was seen. At 20 months follow-up, an osseous bridging at the triradiate cartilage and mild coxa valga deformity developed. We think that every child with serious sacroiliac joint injury should be evaluated for associated triradiate cartilage injury and followed to skeletal maturity for late complications such as acetabular dysplasia, hip subluxation and pelvic asymmetry.