Differences in spatiotemporal landing variables during a dynamic stability task in subjects with CAI.

Chronic ankle instability (CAI) has been previously associated with deficits in dynamic stability and proximal joint neuromuscular alterations separately, but it is unclear how the two factors relate. The purpose of this investigation was to examine the contributions of lower extremity kinematics during an assessment of dynamic stability in subjects with CAI. Thirty-eight subjects were divided equally into those with and without unilateral CAI. Subjects performed 10 single-limb jump landings on each limb. Kinematic position 100 ms pre-impact as well as peak and time-to-peak kinematic position post-impact were recorded for ankle plantar flexion, knee flexion and hip flexion. Ground reaction force data in the A/P and M/L directions were used to calculate the resultant vector time to stabilization (RVTTS). For the RVTTS data, a significant main effect (P=0.03) revealed that the CAI group had significantly reduced dynamic stability. For knee flexion pre-impact, a significant main effect for group (P=0.005) demonstrated that the CAI group prepared to land with less knee flexion than the Control group. Decreased knee flexion angle in preparation to land was apparent in the CAI group, and may play a role in the diminished dynamic stability in CAI subjects.