OBJECTIVE: Objectively evaluate the incidence of sciatic nerve injury after a total hip arthroplasty (THA) performed through a posterolateral approach. METHODS: Patients scheduled to undergo THA were evaluated preoperatively and postoperatively with electrophysiologic studies, the Western Ontario and McMaster Universities Osteoarthritis index (WOMAC) questionnaire and other methods described in the study. Patients older than 21 years with any of the following preoperative diagnoses: primary or secondary osteoarthritis, aseptic avascular necrosis, rheumatoid arthritis, and posttraumatic arthritis were included. Variables used for analysis were sex, age, and body mass index (BMI). The Mann-Whitney U and Wilcoxon tests and, Pearson and Spearman correlation statistics were used for analysis of categorical and continuous data respectively. RESULTS: Electrodiagnostic data showed alterations in 17 patients (70.8%). No signs of sciatic nerve injury. The mean preoperative and postoperative WOMAC scores were 40 and 74, respectively (p = 0.0001). Statistical differences were noted in sural sensory amplitude (SSA) and distal amplitude of the tibialis motor nerve in the female group (p=0.007; p=0.036, respectively). The SSA also demonstrated differences in the obese group (p=0.008). In terms of age, both the SSA (Pearson p=0.010 and Spearman p=0.024) and the proximal latency of the peroneal motor nerve (Pearson p=0.026 and Spearman p=0.046) demonstrated a decrease in amplitude and an increase in latency that was inversely related with age. CONCLUSION: According to our subclinical electrophysiological findings, surgeons that use the posterolateral approach in THA procedures must be conscious of the sciatic nerve's vulnerability to reduce possible clinical complications.