Ankle sprains are a common injury, with affected individuals often experiencing recurrent symptoms that can progress to chronic ankle instability (CAI). Balance impairments are routinely present in subjects with CAI. Changes in tissue structure of the anterior talofibular ligament (ATFL) and superior extensor ankle retinaculum (SEAR) may occur after an ankle sprain, and may contribute to impaired balance through altered proprioception. PURPOSE: To determine if ATFL/SEAR thicknesses were related to dynamic balance in individuals with CAI. METHODS: Subjects were 14 males and 15 females (Age= 24.52 ± 3.46 years). Ankle instability was assessed using the Cumberland Ankle Instability Tool (CAIT), with a cut-off score of 25 to define two groups: those with and without CAI. Real-time ultrasound was used to assess ATFL and SEAR thicknesses. Dynamic balance was measured with the Y Balance Test (YBT) and the NeuroCom® motor control and adaptation tests. For subjects with CAI, we analyzed stable versus unstable ankles; for those without CAI, we analyzed right versus left ankles. RESULTS: There was no difference in mean ATFL thickness (0.24 ± 0.03 vs. 0.22 ± 0.04 cm, respectively, p=0.21) or in SEAR thickness (0.09 ± 0.01 vs. 0.10 ± 0.02 cm, respectively, p=0.19) between the stable and unstable ankles in those with CAI. For those without CAI, there was also no difference between the right and left ATFL thickness (0.22 ± 0.06 vs. 0.20 ± 0.04 cm, p=0.14) or SEAR thickness (0.09 ± 0.01 vs. 0.09 ± 0.01 cm, p=0.95). There was no difference in YBT scores in those with or without CAI (p=0.21, p=0.89 respectively). Additionally, sway energy for upward or downward forces was comparable between those with and without CAI, (p=0.15, p=0.36). Similarly, composite latencies were also no different (p= 0.68). CONCLUSIONS: There was no relationship between ligament thickness and balance, supporting a multifactorial CAI rather than dependency upon tissue changes alone. Central nervous system sensory integration, neuromuscular control compensations, or psychosomatic reactions may be the ones affecting the balance more. Likewise, subject perception of ankle instability may not coincide with impaired dynamic balance. Finally, tests used to assess dynamic balance may not be sensitive enough to identify differences caused by CAI.