Objective To compare the effectiveness of modified distal tibial tubercle-high tibial osteotomy (DTT-HTO) and open-wedge HTO (OWHTO) in the treatment of medial compartment osteoarthritis. Methods A clinical data of 80 patients with medial compartment osteoarthritis treated with HTO between January 2016 and January 2019 was retrospectively analyzed, including 40 patients treated with DTT-HTO (DTT-HTO group) and 40 patients treated with OWHTO (OWHTO group). There was no significant difference in gender, age, body mass index, affected side, disease duration, Kellgren-Lawrence grading of osteoarthritis, and preoperative knee society score (KSS), Hospital for Special Surgery (HSS) score, knee joint visual analogue scale (VAS) score, hip-knee-ankle angle (HKA), posterior tibial slope (PTS), weight-bearing line ratio (WBL), Blackburne-Peel index (BPI), Caton-Deschamps index (CDI), and Insall-Salvati index (ISI) between the two groups (P>0.05). The operation time, incision length, bleeding volume, hospital stay, and complications in both groups were recorded. The KSS, HSS, and VAS scores were used to evaluated the effectiveness. A self-made questionnaire was used to evaluate the recovery of low-impact sports ability of the knee. X-ray films were used to observe the osteotomy healing and measure the HKA, PTS, WBL, and the patellar height indexes (BPI, CDI, ISI). Results All operations successfully completed in both groups. The OWHTO group operated longer than the DTT-HTO group (P<0.05). There was no significant difference in the incision length, bleeding volume, and hospital stay between the two groups (P>0.05). All incisions healed by first intention in both groups. There were 2 cases of lateral hinge fractures in the OWHTO group, and 1 case of lateral hinge fracture and 2 cases of tibial plateau fractures in the DTT-HTO group. No other complications occurred. The patients in both groups were followed up 2-4 years with an average of 2.8 years. The HSS, KSS, and VAS scores in both groups significantly improved after operation when compared with preoperative scores (P<0.05). All scores gradually improved with the time and there were significant differences between different time points (P<0.05). The HSS, KSS, and VAS scores were significantly better in the DTT-HTO group than in the OWHTO group at 3 months after operation (P<0.05). There was no significant difference between the two groups at 6 months, 1 year, and 2 years (P>0.05). At 1 year, the low-impact sports ability of the OWHTO group was rated as excellent in 8 cases, general in 25 cases, and poor in 7 cases, and as excellent in 7 cases, general in 26 cases, and poor in 7 cases of the DTT-HTO group. There was no significant difference between the two groups (Z=−0.715, P=0.475). X-ray film reexamination showed that the osteotomies healed in both groups. The healing time was (4.52±1.23) months in the OWHTO group, and (4.23±1.56) months in the DTT-HTO group, showing no significant difference (t=0.923, P=0.359). At immediate after operation, the HKA and WBL of the two groups significantly improved when compared with the preoperative values (P<0.05). However, the pre- and post-operational difference was not significant between the two groups (P>0.05). The PTS of the OWHTO group was significantly higher than preoperative value (P<0.05), while the PTS of the DTT-HTO group was lower than preoperative value (P>0.05). The pre- and post-operational difference between the two groups was significant (P<0.05). BPI and CDI in the OWHTO group were significantly lower than preoperative values (P<0.05), but there was no significant difference in ISI when compared with preoperative value (P>0.05). There was no significant difference in the BPI, CDI, and ISI of the DTT-HTO group between pre- and post-operation (P>0.05). The pre- and post-operational differences of BPI and CDI between the two groups were significant (P<0.05), and there was no significant difference in the pre- and post-operational difference of ISI (P>0.05). ConclusionThe two osteotomies in the treatment of medial compartment osteoarthritis can significantly change the varus deformity and achieve satisfactory effectiveness. The early functional recovery of DTT-HTO is faster, which can avoid the increased PTS and patellar baja of traditional OWHTO. However, neither of the two surgical procedures can restore the patient’s ideal low-impact sports ability of the knee.