Objective The aim was to analyze the gait of knee osteoarthritis patients before osteotomy. Material/patients and methods Twenty-four patients aged 52.4 years±6.8, 15M/9F, were comparatively analyzed to 24 matched controls. Deficiencies and disabilities were evaluated by means of: numeric pain scale, Lysholm, Koos and Womac and SF-36 scores. They were also asked to estimate their self-perception of gait on a 4-level scale. Spatiotemporal gait parameters were also measured at comfortable speed, using an optical system (otpogait). Results Disabilities were attested by the following data: numeric pain scale of pain 5.7±2.2/10, Lysholm score 58%, SF-36 physical score 31.8%, SF-36 mental score 53.2%, Womac score 46.5/96. As compared to controls, patients perceived their gait alteration (P <10−3), and walked slower (P =10−3), with shorter single support time on affected (P <10−4) and unaffected (P <10−3) sides, longer double support time (P <10−4), and shorter step length for both sides (P <10−3). Discussion–conclusion The assessments describe and quantify the limitation of gait in patients with knee osteoarthritis, and provide objective data to be compared with those after osteotomy.