Objective To evaluate the clinical efficacy, biomechanical stability, and scar recovery of minimally invasive posterior approach for the treatment of posterior cruciate ligament (PCL) avulsion fractures at the tibial insertion. Methods A retrospective cohort study design was adopted. A total of 45 patients with PCL avulsion fractures at the tibial insertion (23 cases of type Ⅱ and 22 cases of type Ⅲ according to the Meyers-Mckeever classification) admitted to the Department of Orthopedics of the Eighth People’s Hospital of Wuxi from June 2021 to April 2025 were included. According to the surgical plan, the patients were divided into an observation group (minimally invasive posteromedial approach, 23 cases) and a control group (traditional inverted L approach, 22 cases). The surgical-related indicators (incision length, operation time, intraoperative blood loss, hospital stay), postoperative complications, bone healing time, knee joint range of motion (ROM) at different time points, visual analogue scale (VAS) for pain, Lysholm score, Tegner score, International Knee Documentation Committee (IKDC) score, scar satisfaction score (VSS), and SF-36 quality of life score were compared between the two groups. Biomechanical stability was evaluated by the posterior drawer test, and subgroup analysis was conducted. Results All patients were followed up for 12 to 24 months, with an average of (16.57±3.58) months. The observation group had significantly better incision length, operation time, intraoperative blood loss, and hospital stay than the control group, and the differences were statistically significant (P<0.05). The VAS scores of the observation group at 1, 3, and 7 days after surgery were lower than those of the control group, with statistically significant difference(P<0.05). Three cases of fat liquefaction occurred in the control group (incidence rate of 13.64%), while there were no complications in the observation group. The difference in complication rates between the two groups was statistically significant. There was no difference in bone healing time between the two groups. The ROM at 1 month after surgery, the Tegner score, IKDC score, and SF-36 score at the last follow-up in the observation group were better than those in the control group, with statistically significant difference (P<0.05); the VSS score at 6 months after surgery in the observation group (1.95±0.74) was lower than that in the control group (4.09±1.05) , and the difference was statistically significant (P<0.05). The proportion of grade I stability in the posterior drawer test at 6 months after surgery in the observation group was 95.65%, significantly higher than 77.27% in the control group. Subgroup analysis showed that patients of different types and age groups could benefit from the modified surgical approach. Conclusions The minimally invasive posterior approach for the treatment of PCL avulsion fractures at the tibial insertion has significant advantages in trauma control, pain relief, hospital stay, functional recovery, biomechanical stability, and scar aesthetics, with a lower complication rate, which is a safe and efficient individualized treatment option.