Background: Recent systematic reviews support that non-operative management should be the standard treatment for all stable isolated lateral malleolar fractures (ILMFs), regardless of fibular fracture displacement. Surgical fixation of ILMFs carries a risk of adverse events (AEs), and many patients will later require implant removal. We wanted to estimate the incidence of AEs requiring revision after surgical fixation of “potentially stable” displaced ILMFs before non-operative treatment became standard care in our department. Materials and methods: To identify patients with “potentially stable” ILMFs who had been treated surgically in a historical cohort, we retrospectively applied the stability-based classification system, introduced by Michelson et al., to a cohort of 1006 patients with ankle fractures treated surgically from 2011 to 2016. The primary outcome of this retrospective cohort study was the incidence of AEs that had functionally significant adverse effects on outcome and required revision in the first 12 months after surgery. AEs were graded and categorized using the Orthopedic Surgical Adverse Events Severity (OrthoSAVES) System. Results: The study population comprised 108 patients with “potentially stable” displaced ILMFs; 4 patients (3.7% [95% CI (0.1–7.3%]) experienced AEs requiring revision in the first twelve months after surgery. There were 5 additional patients (4.6%) with functionally significant AEs where revision surgery was not indicated within the first twelve months after surgical fixation. A further 5 patients (4.6%) had AEs managed in the outpatient clinic (grade II); 36 patients (33.3%) required secondary implant removal due to implant-related discomfort. Conclusions: Surgical fixation of ILMFs carries a risk of severe AEs, and many patients will subsequently need implant-removal procedures. Further prospective studies are required to ascertain whether non-operative treatment can lower the risk of AEs and the need for additional surgical procedures.