BACKGROUND Adult-acquired flatfoot deformity requires a complex operative plan that often utilizes a number of procedures to correct deformity, at both the hindfoot and midfoot. A lateral column lengthening procedure is typically performed to correct abduction deformity across the talonavicular joint; however its effect on hindfoot alignment is not well understood, and overcorrecting the hindfoot deformity can lead to pain and revision surgeries. Therefore, understanding the effect of lateral column lengthening on hindfoot alignment is important for operative planning. The aim of this study was to demonstrate the effect of a lateral column lengthening osteotomy on hindfoot valgus in a simulated flatfoot model. METHODS A flatfoot deformity was created in 12 lower limb cadaveric specimens. A step-cut lateral column lengthening osteotomy was performed and changes in hindfoot and midfoot alignment were measured using a motion capture system. RESULTS The lateral column lengthening procedure corrected 60% of the hindfoot valgus deformity (P < .001). In addition, the abduction deformity at the midfoot was completely corrected with the procedure (P < .001). CONCLUSION Our findings suggest that the lateral column lengthening procedure corrects hindfoot valgus, in addition to midfoot abduction, in a flatfoot deformity. CLINICAL RELEVANCE Understanding the relative contribution of each operative procedure to the overall deformity correction in flatfoot reconstruction will allow surgeons to accurately correct the foot into a plantigrade position while minimizing the risk of overcorrection.