PURPOSE: Recurrence of lateral ankle sprain (LAS) is common among recreational and competitive athletes. Talocrural (TC) joint laxity has traditionally been seen as the cause of mechanical instability after LAS. The purpose of this study was to examine the use of stress fluoroscopy and physical examination in the assessment of TC and subtalar (ST) instability in subjects with and without a history of LAS. METHODS: Twelve subjects with a history of unilateral LAS and eight healthy controls were examined by two blinded examiners. The first examiner performed physical examination on each ankle by using the anterior drawer (AD), talar tilt (TTPE), and medial subtalar glide (MSTG) tests. Laxity in each ankle was assessed on a 4-point scale. The second examiner performed stress fluoroscopy taking AP views with and without a manually applied supination stress to assess TC laxity and a sidelying modified Broden view with and without stress to assess ST laxity. Subjective examination of the images was used to determine excessive TC and ST laxity. RESULTS: Seventy-five percent of previously injured subjects demonstrated unilateral laxity differences of the TC joint using stress fluoroscopy. Of the nine with excessive talar tilt on fluoroscopy, 78% demonstrated excessive laxity with the AD and MSTG tests, and 67% demonstrated laxity with the TTPE test. Sixty-seven percent of those with TC laxity also demonstrated either excessive unilateral or bilateral laxity of the ST joint under stress fluoroscopy. CONCLUSIONS: These data suggest the existence of a subpopulation of patients with a history of LAS who demonstrate a pattern of combined TC and ST laxity.