Objective To investigate the effect of knee suspension during titanium plate fixation on postoperative posterior tibial slope (PTS) in knee osteoarthritis (KOA) with medial opening-wedge high tibial osteotomy (OWHTO). Methods The clinical data of 47 patients with KOA treated by OWHTO between January 2019 and December 2020 was retrospectively analyzed. In 24 cases, the knee joint was suspended when titanium plate was fixed (research group), and in 23 cases, the knee joint was naturally straightened when titanium plate was fixed (control group). There was no significant difference in gender, age, side, body mass index, disease duration, preoperative visual analogue scale (VAS) score, American Hospital for Special Surgery (HSS) score, Western Ontario and McMaster University Osteoarthritis Index (WOMAC) score, Lysholm score, and preoperative PTS between the two groups (P>0.05). PTS were measured at 1 day after operation and last follow-up, and were compared with that before operation. Before operation and at last follow-up, VAS score was used to evaluate the knee pain, HSS score, WOMAC score, and Lysholm score were used to evaluate the knee function. Results The patients in both groups were followed up 13-24 months, with an average of 19.9 months. There was no complication such as incision infection, screw fracture, and deep venous thrombosis of lower limbs in two groups. At last follow-up, the VAS score, HSS score, WOMAC score, and Lysholm score in two groups were significantly improved when compared with those before operation (P<0.05), but there was no significant difference between the two groups in the each score difference of before and after operation (P>0.05). There was no significant difference in PTS at each time point before and after operation in the research group (P>0.05), but PTS in the control group significantly increased at 1 day after operation and last follow-up (P<0.05). PTS of the research group at 1 day after operation and last follow-up were significantly lower than those of the control group (P<0.05). ConclusionOWHTO can effectively relieve knee pain and improve knee function in KOA, and the increase of postoperative PTS can be effectively avoided by suspending knee joint.