Lower limb immobilisation increases venous thromboembolism (VTE) risk. However, as the risk is low (0.6–2%), it is preferable to use a risk assessment tool to determine who should receive prophylaxis.1 Various VTE risk assessments for lower limb immobilisation exist.2 King’s College Hospital (KCH) Trust employs a simple four-item risk assessment tool (the K4 score) (figure 1), which was derived from local expert opinion and implemented in 2016. Risk assessment is a mandatory field during electronic referral from the EDs or urgent care centres (UCCs) to the orthopaedic team. We report VTE risk assessment rate, prescription for weight-based thromboprophylaxis and incidence of VTE within 90 days, over a 2-year period at our Trust, which includes two EDs and their associated UCCs . There was no patient or public involvement in the design, and no ethical approval was required …