Tension band plating is a commonly performed procedure to address angular deformities about the knee in children. We present a case of a synovial fistula formation after tension band plate removal, an unreported complication in the literature. An 11-year-old girl underwent tension band plating for genu valgum. After removal of the plate, she developed a synovial fistula that was confirmed by magnetic resonance imaging. Her knee was immobilized in extension, which allowed the synovial fistula to heal. The unique capsular anatomy in the knee provides a possible etiology. Physicians performing tension band plating should be aware of this complication and consider a brief period of immobilization of 3 to 5 days after hardware removal to allow the capsular rent to heal.