We performed physical therapy after reconstruction of the posterior cruciate ligament (PCL) on a Japanese Taekwondo player. In physical therapy after the reconstruction of PCL, we had to protect PCL from mechanical stress. To protect the reconstructed PCL in this case, we predicted the traction stress for PCL by motion analysis using surface electromyography (EMG). In order to avoid the traction stress on PCL, we checked the muscle activity of the quadriceps femoris and the hamstrings during various kinds of muscle strengthening exercises for the lower extremity in the closed kinetic chain (CKC). The muscle contraction of hamstrings with knee flexion caused the posterior displacement of the tibia, and the traction load on PCL was increased with a contraction of hamstrings. On the other hand, because the muscle contraction of the quadriceps femoris produced anterior sharing force of the tibia, the contraction of the quadriceps femoris could protect the PCL from traction load. Therefore, we selected the muscle strengthening exercises in which the muscle activity of the hamstrings was lower and the muscle activity of the quadriceps femoris was higher. Twelve weeks post operation, the muscle strength of the quadriceps femoris had reached a level compatible with returning to competition, and since the patient had no pain or instability of the knee, we had him perform athletic training (jogging, running, step drill, etc.). He could practice athletic training without any pain or feeling instability of the knee. After 19 weeks post operation, we had him perform kick training gradually under the doctor's permission, and to prevent the hamstrings tearing as well as increasing the performance of kicking, we started him on muscle strengthening exercises of the hamstrings with the kick training gradually. After about 27 weeks post operation, the patient could practice all Taekwondo training without any knee pain or feeling instability of the knee, and after about 43 weeks post operation, he competed successfully in the All Japan Taekwondo Championship and becoming. In conclusion, because we selected the muscle strengthening training avoiding traction load on the PCL, the patient could carry out athletic training and Taekwondo training in safety after the operation.
