P30 The redistribution of lower-extremity joint effort in patients with chronic ankle instability during a forward-side jump

Study Design Single cohort, descriptive. Objectives To investigate the effect of CAI on lower-extremity kinetic and energetic patterns during a forward-side jump. Background Lateral ankle sprains are common sport-related injuries which often lead to chronic ankle instability (CAI). CAI impairs neuromuscular control and dynamic stability of the lower extremity. Skeletal muscles absorb the kinetic energy during the landing phase of jumping. However, little is known how patients with CAI alter lower-extremity joint mechanics and energetics between distal and proximal joints during functional activity. Methods and Measures 100 CAI (22.3±2.2 years, 174.2±9.5 cm, 72.0±14.0 kg, 82.5%±9.0% FAAM ADL, 61.7%±12.8% FAAM Sports, 3.6±1.2 MAII, 4.3±3.0 ankle sprains), and 100 healthy control subjects (22.2±3.0 years, 172.2±13.2 cm, 71.7±18.4 kg, 100.0%±0.0% FAAM ADL, 100.0%±0.0% FAAM Sports, 0.0±0.0 MAII, 0.0±0.0 sprains) performed five trials of a forward-side jump, which was to jump forward to the centre of a force plate, landing on the dominant leg, and then immediately jump to the contralateral side. A functional analysis of variance (FANOVA) was used to evaluate differences between the two groups (CAI and Control) for joint moment (Nm/kg), and power (W/kg) throughout the entire the ground contact phase of the forward-side jump task (α=0.05). If 95% CI bands did not cross the zero line, we considered the difference significant. Results Relative to the control group, the CAI group increased hip joint moment and decreased ankle and knee joint moment during a forward-side jump. The CAI group demonstrated less ankle and knee joint power and greater hip joint power during landing and jumping phases of a forward-side jump. Conclusion CAI subjects altered their jump landing strategy, redistributing joint kinetics and energetics from distal to proximal joints during the forward-side jump task, to compensate for decreased distal joint moment and power. These differences could have injury risk and performance implications.