Nine children who were less than fourteen years old and had open physes and ligament injuries of the knee were studied. Despite an initial thorough physical and roentgenographic evaluation, the full extent of the lesion was determined only at operation in seven of the nine patients. The intercondylar eminence of the tibia was avulsed in five patients, four of whom had associated collateral ligament injuries and a positive anterior drawer sign. Despite surgical repair, all nine patients demonstrated some degree of postoperative ligament instability. This was increased in those patients in whom menisectomy had been performed concomitantly with ligament repair. Although none of the children were symptomatic at the time of writing, development of degenerative arthritis in the future must be considered. Ligament injury must be considered in the differential diagnosis of the child suffering from knee trauma. The association of avulsion of the tibial spine and collateral ligament injury is emphasized.