Background: There is controversy regarding routine prophylaxis for deep vein thrombosis (DVT) in patients treated via a short leg cast or splint following lower extremity trauma. Objectives: The main aim of this study is to evaluate the incidence of DVT and need for chemoprophylaxis in these patients. Materials and Methods: Patients with ankle sprains or stable foot/ankle fractures were entered in this cross-sectional study. Serum D-dimer levels were measured 2 weeks following fixation. If the D-dimer levels were above 0.2 micrograms/ml the test was considered positive and the patient was referred for Doppler ultrasound examination (DUE) to confirm or rule out the diagnosis of DVT. Finally, the incidence of DVT was calculated and the role of predisposing factors was investigated. Results: There were 95 patients with an average age of 38 ± 13.7 (77.9% males); 46 patients had at least one risk factor for DVT. The D-dimer test was positive in 21(22.1%) patients. DVT was confirmed by DUE in 3 patients (3.1%). The incidence of DVT significantly increased in the presence of 3 or more risk factors (P = 0.01). Conclusions: It seems that DVT is not a common complication of below knee fixation and chemoprophylaxis is not necessary when the patient has less than 3 predisposing factors. With 3 or more risk factors chemoprophylaxis and periodic follow-ups must be considered.