Energy dissipation differs between females with and without chronic ankle instability.

Chronic ankle instability (CAI) is associated with altered energy dissipation patterns, but comparisons to lateral ankle sprain (LAS) copers have not been explored. The purpose of this study was to examine differences in relative sagittal plane energy dissipation during a single-leg landing between female CAI and LAS coper participants. We separated 33 females (23.6 ± 4.6 years, 164.3 ± 6.2 cm, 69.4 ± 13.7 kg) into CAI (n = 17) and LAS coper (n = 16) groups. Participants completed 5 single-leg landings followed by a 5-second stabilization. We collected sagittal plane kinematics and joint moments at the ankle, knee, hip, and proximal joints (knee and hip) combined then calculated each joint's energy dissipation at 50, 100, 150, and 200 ms post-landing. We compared the percentage of total energy dissipated by the ankle, knee, hip, and proximal joints during each interval utilizing independent t tests and Cohen's d effect sizes. Statistical significance was set a priori at P < .05. The CAI group had lower relative energy dissipation from the ankle at 50 (24.7 ± 11.5% vs 39.2 ± 11.8%, P < .01, d = 1.25 [0.47, 1.95]), 100 (66.9 ± 19.4% vs 77.7 ± 6.5%, P = .04, d = 0.74 [0.01, 1.42]), and 150 ms (70.7 ± 17.8% vs 81.0 ± 5.7%, P = .03, d = 0.77 [0.04, 1.46]) compared to LAS copers. The CAI group had a greater hip contribution through 150 ms (17.9 ± 10.7% vs 11.7 ± 4.4%, P = .04, d =-0.75 [-1.44, -0.03]) and the proximal joints at 50 (75.3 ± 11.5% vs 60.8 ± 11.8%, P < .01, d = -1.25 [-1.96, -0.47]), 100 (33.1 ± 19.4% vs 22.3 ± 6.5%, P = .04, d = -0.74 [-1.42, -0.01]), and 150 ms (29.3 ± 17.8 vs 19.0 ± 5.7%, P = .03, d =-0.77 [-1.46, -0.04]) compared to LAS copers. Females with CAI may benefit from therapeutic exercises designed to correct a single-leg energy dissipation strategy that relies less on the ankle joint.