Anterior Cruciate Ligament (ACL) rupture is one of the most common and severe sports injuries among the athletes caused by trauma. The standard treatment for ACL rupture patients is Reconstruction Anterior Cruciate Ligament (RACL) surgery, followed by rehabilitation lasting six to nine months. Consistent post-RACL medical rehabilitation can restore normal knee function. In this study, proposes a real-time simulation of knee joint angle estimation from electromyogram (EMG) signals for medical rehabilitation of RACL patients. Which is the continuation of this program is to be able to create an exoskeleton to increase the consistency and quality of medical rehabilitation of RACL patients. The method used to make this simulation is using LabVIEW software to simultaneous data collection between the EMG signal from the bicep femoralis muscle and the knee angle. The simultaneous data is processed using a Monte Carlo calculation to estimate the knee angle from the EMG signals. The LabVIEW simulation shows that the knee angle's estimate was close enough to the measured knee angle and had a small time delay. It can be concluded that simulation of knee angle estimation from the EMG signal produces a good simulation and can be developed to the exoskeleton.