Rupture of the anterior cruciate ligament (ACL) is a frequent and disabling injury in pivot sports, leading to knee laxity and instability, reduced performance and an increased risk of early osteoarthritis. The risk is 2 to 8 times higher in women, linked to greater ligament laxity and a different quadriceps/hamstring muscle ratio post-puberty. To assess knee laxity and the degree of ligament damage, anterior tibial translation (of the tibia below the femur) is usually measured. This translation is symmetrical and varies between 3 and 10 mm depending on the individual (natural laxity). It is increased in cases of ACL damage. Measuring tibial rotation is also of interest in this context. Studies show that the ACL plays a crucial role in controlling internal and external tibial rotation, especially during low-flexion movements (between 10° and 30°). ACL rupture also significantly increases this rotation, aggravating knee instability. It therefore seems important to study both tibial rotation and tibial translation to assess knee laxity. Combining these two measurements seems to improve diagnostic accuracy. This multifactorial approach could provide additional information on biomechanical abnormalities and predisposition to injury. The use of biomechanical data, such as normative values for tibial rotation, is fundamental to prevention, and preventive exercise programs reduce the risk of rupture4. Defining these norms would help identify athletes at risk and personalize preventive strategies. Instrumented assessment of laxity, using devices such as the DYNEELAX dynamic arthrometer, enables precise quantification of tibial rotation and anterior tibial translation under controlled loads. Its reliability has been proven5 and its use has been mastered at Toulon (Unité de Médicine et Traumatologie du Sport) and Brest (Centre de Médecine du Sport). It will be used in the PRELAX project to define normative tibial rotation values.