The cases of seven patients who had a physeal arrest about the knee in association with nonphyseal fractures in the lower extremity were reviewed. The patients were between ten and twelve and one-half years old at the time of injury, and the physeal arrest involved either the posterolateral part of the distal femoral physis or the anterior part of the proximal tibial physis. There was no evidence of iatrogenic trauma to the physis. Recognition of the physeal injury was delayed for an average of one year and ten months until a gross angular deformity appeared. Adolescents who have fractures of the lower extremities that do not appear to involve a physeal plate should nevertheless be evaluated and followed for possible physeal injury about the knee that can be detected only after additional growth has taken place.