Background Lower extremity vascular trauma (LEVT) is a major cause of amputation. A clear understanding of prognostic factors for amputation is important to inform surgical decision-making, patient counselling and risk stratification. The aim was to develop an understanding of prognostic factors for amputation following surgical repair of LEVT. Methods A systematic review was conducted to identify potential prognostic factors. Bayesian meta-analysis was used to calculate an absolute (pooled proportion) and relative (pooled odds ratio, OR) measure of the amputation risk for each factor. Results Forty-five studies, totalling 3187 discrete LEVT repairs, were included. The overall amputation rate was 10·0 (95 per cent credible interval 7·4 to 13·1) per cent. Significant prognostic factors for secondary amputation included: associated major soft tissue injury (26 versus 8 per cent for no soft tissue injury; OR 5·80), compartment syndrome (28 versus 6 per cent; OR 5·11), multiple arterial injuries (18 versus 9 per cent; OR 4·85), duration of ischaemia exceeding 6 h (24 versus 5 per cent; OR 4·40), associated fracture (14 versus 2 per cent; OR 4·30), mechanism of injury (blast 19 per cent, blunt 16 per cent, penetrating 5 per cent), anatomical site of injury (iliac 18 per cent, popliteal 14 per cent, tibial 10 per cent, femoral 4 per cent), age over 55 years (16 versus 9 per cent; OR 3·03) and sex (men 7 per cent versus women 8 per cent; OR 0·64). Shock and nerve or venous injuries were not significant prognostic factors for secondary amputation. Conclusion A significant proportion of patients who undergo lower extremity vascular trauma repair will require secondary amputation. This meta-analysis describes significant prognostic factors needed to inform surgical judgement, risk assessment and patient counselling.