Thromboprophylaxis in Lower Limb Immobilisation

Inclusion Criteria: * Age \>/= 16 years * Placed in temporary lower limb immobilisation (rigid cast or brace) as a result an injury that occurred within the last 7 calendar days Exclusion Criteria: * Hospital admission is required direct from the emergency department, minor injuries unit, or fracture clinic setting with an expected length of stay \>2 calendar days. * Absolute contraindication or known hypersensitivity to anticoagulants, including history of end stage renal failure (eGFR \<20ml/min/1.73m2), hepatic failure or use of concomitant systemic treatment with azole-antimycotics (such as ketoconazole, itraconazole, voriconazole and posaconazole), HIV protease inhibitors (e.g. ritonavir) or active substances strongly inhibiting elimination pathways such as CYP3A4 or P-gp (such as clarithromycin, erythromycin or dronaderone) or a history of heparin induced thrombocytopenia. * Pregnancy, actively seeking conception, or active breastfeeding. * Preceding use of anticoagulant treatment for \>3 calendar days at prophylactic or therapeutic dose. * Prior enrolment in the TiLLI study. * Non-rigid immobilisation (crepe bandage, tubigrip support, strapping). * Time since prescription of rigid immobilisation \>3 calendar days * Co-enrolment onto a CTIMP where an anticoagulant is administered * People lacking the capacity to consent * Inability or refusal to use acceptable contraception up until after the last administration of IMP. Only applicable for women of childbearing potential who have been randomised to receive apixaban or rivaroxaban