Extensive histological studies have now confirmed a definite link between the anterior cruciate ligament (ACL) and the central nervous system. Preliminary histological evidence indicates that this neurological connection may be restored following reconstruction utilizing a free graft. In spite of this apparent graft reinnervation, clinical studies indicate that proprioception in the reconstructed knee probably remains inferior to that of the contralateral normal knee. A number of abnormalities of gait, reflexes, and muscle firing patterns have been discovered following an ACL tear. The degree to which a successful repair or reconstruction corrects these abnormalities remains uncertain, but again it appears that some abnormalities remain even during normal walking. Increased activity of the hamstrings as well as of the vastus lateralis, tibialis anterior, and medial gastrocnemius seems to be an adaptive mechanism to stabilize the knee after ACL injury. These muscle firing patterns seem to be trainable to some degree and should be incorporated into postinjury and postsurgical rehabilitation protocols.