It has been reported that chronic dental lesions such as dental caries, tooth erosions, periodontal diseases, occlusion disorders, temporomandibular joint disorders, and orofacial injuries are common in athletes and this situation negatively affects both general health and sports performance. Our study aims to compare the isokinetic muscle strength of the knee joint in athletes with and without periapical lesions which are chronic dental lesions in the mouth. 32 athletes with periapical lesions (n=16; study group), same gender, similar demographic characteristics, and no periapical lesions(n=16; control group) were included in the study. All athletes were examined by the same dentist using a disposable examination set and evaluated with panoramic radiography. Athletes with periapical lesions after examination and radiological evaluation as the study group; athletes without periapical lesions were determined as the control group. Then, the muscle strength of the knee joint flexor and extensor muscles of the athletes was evaluated concentrically with the IsoMed 2000 isokinetic dynamometer. Isokinetic muscle strength comparisons of the study and control groups were analyzed according to the distribution status by Independent Samples T-test, Mann Whitney-U test. The level of significance was taken as p<0.05. Concentric isokinetic muscle strengths of knee joint flexor and extensor muscles were found to be similar at 60º/sec and 180º/sec angular velocities of study and control group athletes(p>0.05). We can say that the concentric isokinetic muscle strength of the knee joint of athletes with periapical lesions in the mouth and without periapical lesions was not affected negatively.