BACKGROUND: Medial meniscus (MM) translates and extrudes posteriorly during knee flexion in MM posterior root tear (MMPRT) knees, and transtibial pullout repair of MMPRT has been performed to regulate the MM extrusion. This study aimed to calculate each suture translation during knee flexion in transtibial pullout repair of MMPRT, and to investigate the morphologic features of the MM that lead to longer suture translations during knee flexion. METHODS: Thirty patients with MMPRT who met the operative indication of pullout repair were enrolled and investigated prospectively. Pullout repair was performed by using two simple stitches (outer and inner sutures) and an all-inside suture in the posteromedial part of the MM. Each suture's translation from 0° to 90° of knee flexion was measured intraoperatively. The MM morphologic features, including MM medial extrusion (MMME) and MM posterior height (MMPH), were measured using preoperative magnetic resonance imaging, and the correlation between these values and each suture translation was evaluated. RESULTS: The average outer, inner, and all-inside suture translations were 4.8 mm, 3.9 mm, and 1.3 mm, respectively. Significant correlations were observed between the outer suture translation and MMME, and MMPH (p < 0.001 and <0.01, respectively). The thresholds for preoperative MMME and MMPH for longer outer suture translations (≥6 mm) were 2.1 mm and 5.4 mm, respectively. CONCLUSIONS: Preoperative longer MMME and higher MMPH were associated with longer meniscus translations during knee flexion during MMPRT repair.