The relationship between exercise and knee ligament laxity has been explored to some degree in recent research. However, previous studies have focused on athletes participating in a variety of sporting activities with great variance in exercise bouts. This study evaluated anterior cruciate ligament laxity, using the KT‐1000 knee ligament arthrometer, in 50 male and female basketball players before and immediately after a controlled muscular fatiguing isokinetic exercise protocol. Significant pre‐and postexercise differences (p<0.05) in ligament laxity were seen in the combined group of males and females only at 25°±5°of knee flexion with 15 to 20 pounds of anterior displacement (left leg) and 20 pounds of posterior displacement (right leg). In the male athletes, significant pre‐and postdifferences were found at 25°±5°of knee flexion with 15 and 20 pounds of anterior displacement (left leg). No significant before to after differences were observed among female athletes.