Proprioception can be described as the combination of awareness of joint movement and position in space. Ruffini receptors, Vater Pacini receptors, Golgi tendon organs and free-nerve endings have been observed in human ACL and it is believed that these mechanoreceptors have a proprioceptive function and provide the afferent arc for signaling knee postural changes. Recently, direct evidence of anterior cruciate ligament-hamstring reflex arc has been shown in humans which strongly supported the concept of ACL is as a part of afferent ligamentous-neural-muscular arc to regulate the knee muscle stiffness and control the dynamic joint stability. In the injured knee this afferent ligamentous-neural-muscular arc is broken, thus significant decrease in proprioception after an ACL injury has been reported by several studies. Following ACL rupture, it was suggested that loss of proprioception is not only due to loss of afferent input through ACL but also due to altered joint kinematics. Proprioceptive deficits have been documented in both the injured and non-injured knees of unilateral ACL rupture and several studies reported that proprioceptive deficits improve after an ACL reconstruction regardless of the graft type used. It seems that impaired proprioception is related to reduced functional ability in ACL injured patients, and although good knee functions and activity level can be achieved after a supervised rehabilitation program in non-operated patients, proprioception of the knee is not restored.