Imbalances between the agonist-antagonist muscles of the knee have been linked to a greater susceptibility to injury in the knee joint. The aim of the present study was to assess the Hamstring/Quadriceps muscular strength (H/Q) ratio of elite karate athletes before and after muscular fatigue. Thirteen female elite karate athletes (age: 15.5±1.5 years) were evaluated in an isokinetic dynamometer at 60◦/s, 180◦/s and 300◦/s before and after hamstring and quadriceps muscular fatigue. Paired sample T-test and one way repeated measure were used for statistical analysis. α level was set at 0.05. After muscular fatigue, significant decrease were found in Hamstring/Quadriceps muscular strength ratio in the knee flexors and extensors strength (P>0.05) at the 60◦/s, 1800◦/s and 300◦/s speeds (P<0.05). No significant difference was found in the knee (H/Q) ratio between three different speeds (F=1.23; P=0.30). Our results showed that lower limb muscle imbalances in elite female karate athletes that could predispose young karate athletes to injuries exist at the speed of 300◦/s speed and in three different speeds after fatigue protocol, but there are not any differences after fatigue between three speeds. So we can say that fatigue can probably increase the potential of knee joint injury and particularly ACL structure.