Background: Hamstring strain injury (HSI) is one of the most common sport injuries with long term complications and poor function subsequently. Hamstring has an important role in knee joint biomechanics and it has proven that some severe knee injuries such as ACL injury increases the risk of HSI; therefore, the functional deficits and knee joint biomechanical changes that occur after HSI need to be considered. Purpose: The aim of this study was to compare the kinetics and kinematics factors of the knee in sagittal plane at single leg jump-landing task, in athletes with previous HSI. We compared healthy and injured leg and also the injured leg with healthy subjects (control group). Methods: In this study 32 college athletes (16 healthy subjects and 16 patients with previous HSI) participated. All participants in HSI group had history of acute hamstring strain more than 3 months, without any other lower extremity injury and they had returned to sport after rehabilitation and functional training. None of the participants had history of ACL injury previously. All of them did single leg jump-landing task, 3 trial for each leg of HSI group and matched leg of healthy ones. Then their knee kinetic and kinematic recorded by six high-speed (200 Hz) cameras (JVC) and force plate. Knee angle and moment in sagittal plane, posterior ground reaction force (PGRF) and knee muscles power in sagittal plane were compared between two legs of injured group and compared with healthy subjects, at initial contact and maximal events of landing. After data collection, statistical analysis such as paired T-test, Wilcoxon for comparing two legs of HSI group, and student T-test and manvitney were used for comparing HSI and healthy groups (α≤ 0.05). Results: There were no significant differences in knee joint kinematic and kinetics between hamstring injured leg and healthy group (p˃0.05). There were significant differences in extensor force to posterior ground reaction force ratio (EF/PGRF), and
