Kim KI, et al. - One-hundred and sixty-nine knees that underwent medial open-wedge high tibial osteotomy (MOWHTO) for treatment of varus osteoarthritis with a minimum follow-up of three years were recruited in a study by the researchers in order to examine the incidence, degree, and natural course of lateral numbness post-MOWHTO and assess which predisposing factors would influence lateral numbness following MOWHTO. At six weeks postoperatively, lateral numbness was seen in 87 knees. Eighteen knees exhibited no improvement to the latest follow-up, however, 69 knees got better over time. The level of skin incision demonstrated a marked correlation with lateral numbness on univariate and multivariate analyses, ie, the higher the level of skin incision, the greater the degree of estimated numbness. Hence, following MOWHTO, about half the cases reported postoperative lateral numbness in the lower leg, out of whom, approximately one-fifth remained symptom until the last follow-up. Moreover, for lateral numbness, the level of skin incision could be a risk factor. Pre-operative subject guidance concerning the likelihood of lateral numbness was suggested.