Understanding the morphological, movement, and biomechanical characteristics that influence rearfoot motion during lateral movements is necessary for footwear design and for the determination of injury mechanisms. The purpose of this study was to identify factors related to rearfoot kinematics during a lateral braking movement. Seven highly skilled male tennis players performed 24 trials of side shuffle movements at various speeds. A rear view of the right leg performing a braking step onto a force platform was filmed. The neutral-O landing style was most commonly demonstrated. Average movement velocity, foot velocity at touchdown, and body mass were variables demonstrating weak or nonsignificant correlations with the rearfoot parameters. Although structural inversion was correlated significantly with the maximum rearfoot angle and velocity (r = -0.52 and -0.69), the results were affected by movement speed and sample size. The biomechanical characteristics displayed the greatest influence on the various rearfoot kinematic parameters. The magnitude of the significant (P less than 0.0001) correlations generally decreased in the following order: maximum horizontal and vertical force gradients, corresponding times to the maximum gradient values, maximum horizontal and vertical forces, and the corresponding times to maximum forces. In conclusion, the gradient-associated parameters were the most useful biomechanical parameters for predicting changes in rearfoot kinematics.