Background Treatment of anterior cruciate ligament rupture in adolescents with open physes is controversial. Hypothesis Delaying reconstruction until the physes bridge will affect the rate of additional knee injuries. Study Design Case control. Methods The physes group was 13 adolescents with open physes whose anterior cruciate ligament reconstructions were delayed until their physes bridged. Specific types of activity were absolutely restricted during the delay. The physes groups’ rates of additional injuries, identified arthroscopically at reconstruction, were compared to rates among 116 skeletally mature adolescents. The comparison adolescents were stratified into four groups by interval from injury to reconstruction (< 1 week, 1 to 6 weeks, 6 to 26 weeks, >26 weeks). Results The additional injury rates in the physes and four comparison groups were 46%, 50%, 47%, 43%, and 69%, respectively. Severity of additional injury, mechanism of injury, and rate of additional surgical procedures were similar among the groups. Conclusions There was no evidence that intentionally delayed anterior cruciate ligament reconstruction increased the rate of additional knee injuries. Delayed reconstruction is a valid treatment option for adolescents with open physes at injury. Absolute activity restriction is key to decreasing the risk of additional knee injuries.