Foot Kinematics Differ Between Runners With and Without a History of Navicular Stress Fractures

BACKGROUND: A navicular stress fracture (NSF) is a common and high-risk injury in distance runners. It is not clear whether there are differences in foot structure and function between runners who have and those who have not sustained an NSF. PURPOSE/HYPOTHESIS: This study compared foot structure, range of motion, and biomechanics between runners with a history of unilateral NSFs and runners who had never sustained this injury. The hypothesis was that runners with a history of NSFs will have less dorsiflexion and subtalar range of motion in a clinical examination and greater rearfoot eversion and higher eversion velocity while running than either the noninvolved feet or healthy controls. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: Seven runners who sustained an NSF were matched with 7 controls without this injury history. Participants underwent a clinical orthopaedic examination, followed by a 3-dimensional running gait analysis. Clinical examination variables, foot kinematics, and ground-reaction forces were compared between injured and noninjured feet within the NSF group and between the NSF group and control group. RESULTS: The NSF group demonstrated less plantar flexion on the clinical examination than the control group (P = .034, effect size [ES] = 0.69). The involved feet of the NSF group demonstrated greater rearfoot eversion excursion, greater eversion velocity, and reduced forefoot abduction excursion than either the noninvolved feet of the NSF group (P = .015, ES = 1.73; P = .015, ES = 1.86; and P = .015, ES = 0.96, respectively) or the control group (P = .012, ES = 1.40; P = .016, ES = 0.49; and P = .005, ES = 1.60, respectively). CONCLUSION: There are differences in foot kinematics but not ground-reaction forces, foot structure, or passive range of motion between runners who have and those who have not sustained an NSF. Runners who demonstrate increased rearfoot eversion and reduced forefoot abduction during stance may be more at risk for developing NSFs.