Active ankle motion may result in changes to the talofibular interval in individuals with chronic ankle instability and ankle sprain copers: a preliminary study.

INTRODUCTION: Alterations in talocrural joint arthrokinematics related to repositioning of the talus or fibula following ankle sprain have been reported in radiological and clinical studies. It is unclear if these changes can result from normal active ankle motion. The study objective was to determine if active movement created changes in the sagittal plane talofibular interval in ankles with a history of lateral ankle sprain and instability.

METHODS: Three subject groups [control (n = 17), ankle sprain copers (n = 20), and chronic ankle instability (n = 20)] underwent ultrasound imaging of the anterolateral ankle gutter to identify the lateral malleolus and talus over three trials. Between trials, subjects actively plantar and dorsiflexed the ankle three times. The sagittal plane talofibular interval was assessed by measuring the anteroposterior distance (mm) between the lateral malleolus and talus from an ultrasound image. Between group and trial differences were analyzed with repeated measures analysis of variance and post-hoc t-tests.

RESULTS: Fifty-seven subjects participated. A significant group-by-trial interaction was observed (F4,108 = 3.5; P = 0.009). The talofibular interval was increased in both copers [2.4±3.6 mm; 95% confidence interval (CI): 0.73-4.1; P = 0.007] and chronic ankle instability (4.1±4.6 mm; 95% CI: 1.9-6.2; P = 0.001) at trial 3 while no changes were observed in control ankle talar position (0.06±2.8mm; 95% CI: -1.5-1.4; P = 0.93).

DISCUSSION: The talofibular interval increased only in subjects with a history of lateral ankle sprain with large clinical effect sizes observed. These findings suggest that an alteration in the position of the talus or fibula occurred with non-weight bearing sagittal plane motion. These findings may have diagnostic and therapeutic implications for manual therapists.