Despite several anatomical and neurophysiological studies have demonstrated the sensory role of anterior cruciate ligament (ACL), it is still unclear how significant the absence of the ACL will affect knee proprioception. Also because some mechanoreceptors has been discovered in the injured bundle commonly resected during ACL reconstruction.

In fact recently it has been observed that subjects with long standing ACL deficiency have not a knee joint pro-prioceptive deficit as measured by threshold of passive movement detenction and the ability to reproduce flex-ion angles, commonly accepted methods.

The aim of this study was to investigate the possibility to recognize a sensorial and behavior impairment in ACL deficient knee.

Through a computerized device the kinaesthetic data were collected from 120 sportsmen between 20–49 years (mean 32,4) affected by unilateral isolated ACL injury diagnosed with MRI and verified arthroscopically. The protocol consisted in four exercises, two bipodal on static and dynamic stance and two monopodal on healthy and injured lower limb. The balance index was divided in four areas on two dimensional plane for a qualitative assessment.

The mathematical and statistical elaboration revealed on bipodal static test a significant and costant displacement on the left side indipendently by the injured side and age. The kinaesthetic awarness was confirmed also by a significant increase of balance index in all exercises. Further studies are necessary to a better knowledge as a possible new tool.

In conclusion, this is the first report of a typical sensorial and behavior impairment in ACL deficient knee with intriguing clinical significance.