May this never happen to your child. Gretchen Reynolds, the fabulous New York Times’ phys. ed. writer shares her experience in helping get treatment for her son who suffered the “terrible triad” while training on a trampoline: he ruptured his A.C.L., tore his medial collateral ligament, and frayed one of his “menisci,” (cartilage in the knee). Even if you’re a couch potato, this is a gripping story — and a good reminder to be engaged in whatever medical treatment you seek.