Background and objectives:Discoid lateral meniscus (DLM) is the most common congenital variant of a meniscus with a high prevalence meniscal tear due to abnormal shape and behavior. The proximal tibiofibular joint (PTFJ) has an important role during knee extension and ankle dorsiflexion. The aim of this research is to study the association between PTFJ morphology in MRI and DLM and its pathologies as compared with the normal lateral meniscus in Iranian population. Materials and methods:Totally, 1729 MRI scans were reviewed, and 69 scans were selected based on inclusion/exclusion criteria. A group of aged-matched control patients without DLM were also included in this study. MRI scans were studied for DLM, meniscal tear and PTFJ inclination angle (horizontal or oblique). Findings were compared with those of patients without DLM. Results:The frequency of horizontal-type PTFJ was significantly higher in the DLM group than in the control group. We also found a strong association (p value=0.018) between horizontal-type PTFJ and meniscal tear as compared with oblique-type in patients with DLM. Conclusion:Horizontal-type PTFJ is more prevalent in patients with DLM. The meniscal tear is also more frequently seen in patients with DLM and horizontal-type PTFJ. Larger prospective studies are needed to confirm these results.