Assessment of Knee Kinetic Symmetry Using Force Plate Technology.

CONTEXT: Athletes who have undergone an anterior cruciate ligament reconstruction often demonstrate more pronounced interlimb knee kinetic symmetry in comparison with uninjured athletes, even after they have completed rehabilitation. Part of the reason for the persistent asymmetry may be that sports medicine professionals are typically not able to assess knee joint kinetics within the clinic setting. Developing measures to assess knee joint kinetic symmetry could help to augment current rehabilitation practices.

OBJECTIVE: The purpose of this study was to explore the extent to which interlimb vertical ground reaction force (GRF) symmetry can predict knee kinetic symmetry during a drop landing task.

DESIGN: Cross-sectional study.

SETTING: Motion analysis laboratory.

PARTICIPANTS: A total of 21 uninjured subjects (9 males and 12 females).

PROTOCOL: Three-dimensional kinematic data were collected using a multicamera system while subjects performed double-leg drop landings. GRF data were collected synchronously using 2 adjacent force plates.

MAIN OUTCOME MEASURES: Knee joint moments and power were calculated for both limbs during the landing trials. An interlimb symmetry index (dominant/nondominant limb) was calculated for both the peak knee joint moment and power variables, as well as for the peak vertical GRFs. Linear regression analyses were performed to determine if the degree of symmetry in the peak vertical GRFs predicted the degree of symmetry for the kinetic variables.

RESULTS: The symmetry index for the vertical GRFs was a significant predictor of the symmetry indices for the knee joint moments (r = .81; P < .001) and power (r = .88; P < .001).

CONCLUSION: Interlimb symmetry in the peak vertical GRFs can be used to predict knee joint kinetic symmetry during a double-leg drop landing task.