Hamstring Stiffness After Anterior Cruciate Ligament Reconstruction

The role of hamstring has been studied in anterior cruciate ligament (ACL) injury prevention, mainly to counteract the anterior tibial translation , especially when contracting eccentrically, but also with passive stiffness. However, little is known about the passive hamstring stiffness after ACL reconstruction (ACLR). The primary objective of this study is to evaluate the passive stiffness of hamstring muscles after ACLR by using an isokinetic device. Secondary, we aimed to test the individual and surgical characteristics associated with hamstring stiffness and the impact of hamstring stiffness on RTS and knee re-injury. The hypotheses are that hamstring stiffness will be lower in the ACLR leg compared to the uninjured leg and to healthy individuals. Also, we hypothesized that hamstring stiffness will be lower after hamstring autograft compared to patellar tendon autograft and will increase progressively after ACLR to be symmetrical at the time for RTS. Also, we hypothesized that hamstring stiffness could be associated with better outcomes at RTS (RTS at same level and lower re-injury rates)