Alterations in knee kinematics and dynamic stability associated with chronic ankle instability

Context: Chronic ankle instability (CAI) has been previously and separately associated with deficits in dynamic stability and proximal joint neuromuscular alterations, but how the 2 factors relate is unclear. Objective: To examine the contributions of lower extremity kinematics during an assessment of dynamic stability in participants with CAI. Design: Repeated-measures case-control design. Setting: Research laboratory. Patients or Other Participants: Thirty-eight volunteers were categorized into groups of those with unilateral CAI (10 men, 9 women; age = 20.3 ± 2.9 years, height = 1.77 ± 0.1 m, mass = 76.19 ± 13.19 kg) and those without (10 men, 9 women; age = 23.1 ± 3.9 years, height = 1.72 ± 0.1 m, mass = 72.67 ± 16.0 kg). Intervention(s): Participants performed 10 jump landings on each limb with a rest period between test limbs. Main Outcome Measure(s): Ankle plantar flexion, knee flexion, and hip flexion were captured with an electromagnetic tracking device at the point of ground impact. Ground reaction force data were used to calculate time to stabilization in the anteroposterior and mediolateral planes. Results: For the anteroposterior plane, we found a group-byside interaction (P = .003), with the injured side of the CAI group demonstrating reduced dynamic stability. For knee flexion, a group main effect (P = .008) showed that the CAI group landed with less knee flexion than the control group. Conclusions: Diminished dynamic stability and decreased knee flexion angle at initial contact were apparent in the CAI group and may play a role in contributing to CAI. This altered kinematic pattern may influence preventive and therapeutic interventions for those with CAI.