Fracture patterns in 87 interphalangeal joint fractures in children's hands were studied and correlated with unique anatomic features of these joints. The collateral ligaments, which extend beyond the physis into the metaphysis, were found to protect the growth plate in the frontal plane. With laterally directed forces, fractures on the proximal side of the joint occurred, rather than epiphyseal fractures. There was good remodeling of angular deformities in the sagittal plane, but minimal correction in the frontal plane. In those patients treated surgically, angular deformities did not result. Of 24 condylar fractures followed for an average of 55 months, 11 (46%) demonstrated some restriction of joint motion.