Signs of impaired neuromuscular communication at 6 h after anterior cruciate ligament (ACL) injury. Representative images of vastus lateralis muscles stained with neural cell adhesion molecule (NCAM; A). NCAM+ cell abundance (B) for vastus lateralis muscles of rats without injury (control) and at 6, 12, 24, and 48 h and 1, 2, and 4 wk after ACL injury. Mean fiber cross-sectional area (CSA; C) for NCAM+ fibers (bars) compared with mean fiber CSA of all fibers (red lines) for rats without injury (control) and at 6, 12, 24, or 48 h or 1, 2, or 4 wk following ACL injury. Values are means ± SE. $P < 0.05, difference from control.