TY - JOUR T1 - 19 Lateral ankle joint complex stiffness in those with chronic ankle instability JF - British Journal of Sports Medicine JO - Br J Sports Med SP - A8 LP - A8 DO - 10.1136/bjsports-2015-095573.19 VL - 49 IS - Suppl 1 AU - CN Brown AU - CO Samson AU - KL Hsieh AU - J Ko Y1 - 2015/10/01 UR - http://bjsm.bmj.com/content/49/Suppl_1/A8.1.abstract N2 - Background The in-vivo status of lateral ankle joint complex laxity and stiffness in chronic ankle instability (CAI) is unclear and may contribute to repeated injury.Objective To determine if differences exist in beginning- and end-range stiffness during anterior loading between various ankle injury groups.Design Cross-sectional.Setting Biomechanics Laboratory.Participants From 52 recreational athletes, 40 meeting the inclusion criteria were divided into control (n = 17), coper (n = 7), mechanical ankle instability (MAI; n = 6) and functional ankle instability (FAI; n = 10) groups (17 males; 23 females; 22.2 ± 3.2 years, height 168.4 ± 10.3 cm, body mass 68.3 ± 15.8 kg). Controls (no ankle injury) and copers (1 sprain from which they recovered) reported Cumberland Ankle Instability Tool (CAIT) scores ≥29. MAI and FAI groups had repeated episodes of giving way and CAIT scores ≤24. The MAI group had anterior displacement >18 mm with arthrometer testing with the FAI group having <18 mm.Interventions Three trials of an instrumented arthrometer anterior load to 150N were applied.Main outcome measurements Anterior displacement (mm) at 150N and stiffness (N/mm) values at beginning- (40–60N) and end-range (125–150N) were extracted and averaged. One-way ANOVAs with Tukey post-hoc comparisons (α = 0.05) were applied. Results Groups were not different in age, height, or body mass. The MAI group had significantly lower stiffness values at beginning-range (3.1 ± 0.6 N/mm, p < 0.007) than controls (4.4 ± 1.0 N/mm) and FAI (4.8 ± 0.6 N/mm) and at end-range (4.3 ± 0.5 N/mm, 5.5 ± 0.9 N/mm, 6.0 ± 0.6 N/mm, respectively, p < 0.01). There were no other group differences.Conclusions The MAI group demonstrated decreased stiffness at beginning- and end-range compared to control and FAI groups. There were no differences in stiffness among control, coper, and FAI groups. For the MAI sub-group with laxity, decreased stiffness may indicate poor joint complex response to loading. Changes in ankle joint complex laxity and stiffness may play a role in repeated injury in some sub-groups of CAI. ER -