BACKGROUND The purpose of this retrospective study is to analyze the effect of different variables on union rate and functional outcome in patients who underwent arthroscopic ankle fusion for end-stage arthritis of ankle. METHODS Clinical records and radiographs were reviewed to evaluate the variables that could predispose patients to non-union and poor functional outcome. Union and functional outcomes were correlated with different variables. RESULTS Fifty patients had arthroscopic ankle fusion on 52 ankles. The mean age at the time of surgery was 59.4 (27-80) years and mean length of follow up was 32.1 (8-78) months. Forty-eight out of 52 ankles (92.3%) achieved radiographic and clinical union. The average time to fusion was 12.2 (8-28) weeks. The time taken for union was significantly higher in smokers as compared to non-smokers (p<0.001). All the patients in this series who had non-union shared one common factor - neuromuscular imbalance. Age, gender, smoking, diabetes, steroid, bisphosphonates, neuropathy, frontal and sagittal plane alignment and tibial-axis-to-talus (T:T) ratio did not significantly affect the union rate and functional outcome. CONCLUSION Smokers should refrain from smoking before surgery and patients with neuromuscular problems may require more rigid fixation and a longer period of immobilization to achieve more consistent union rates.