Cross Bracing Protocol Versus Surgery for Acute Anterior Cruciate Ligament Rupture

Inclusion Criteria: * Aged 16 to 40 years; * Have a primary and acute ACL rupture (complete tear) confirmed by MRI scan; * At least moderately active before the ACL injury (a score of 5 to 10 on the Tegner Activity Scale before the injury); * Willing and able to give informed consent and participate fully in the interventions and assessment procedures; * Willing and able to cover the out-of-pocket costs associated with ACLR surgery. Exclusion Criteria: * Have not completed the baseline questionnaire within 16 days of their initial ACL injury; * Inability to read and speak English * Concomitant knee injury diagnosed on MRI that requires surgical opinion and/or alterative treatment: i) Loose body ii) Unstable osteochondral defect iii) Intra-articular fracture that extends into the articular surface and requires reduction iv) Displaced and/or unstable meniscal tear v) Grade 2 and 3 posterolateral corner injury vi) High-grade medial collateral ligament (MCL) injury that requires treatment with a knee brace and/or surgery vii) Posterior cruciate ligament (PCL) injury (partial discontinuity with some preserved fibers or complete disruption) * Severe disruption of ACL tissue visible on MRI: i) Gap distance ≥8mm and ≥ 25% of tissue displaced outside of intercondylar notch ii) Gap distance ≥8mm and ≥ 25% of femoral footprint avulsed iii) ≥ 25% of femoral footprint avulsed and ≥ 25% of tissue displaced outside of intercondylar notch iv) Complete femoral or tibial avulsion * Concomitant patellofemoral joint dislocation diagnosed on MRI and/or self-reported history of recurrent patellofemoral joint instability or ≥1 patellofemoral joint dislocation; * Self-reported episode of instability (i.e. 'giving way') since initial MRI that resulted in increased pain, swelling and reduced function (without a subsequent MRI to re-determine eligibility); * Open growth plate of the femur and/or tibia visible on MRI; * Past history of ACL injury on the ACL-injured knee; * Past history of any surgery on ACL-injured knee; * Breastfeeding, pregnancy or planned pregnancy within the first 12 weeks of the trial; * Health conditions/medications that are contraindications for ACLR, CBP and/or use of anticoagulant (rivaroxaban) medication: i) Current deep vein thrombosis (DVT); ii) Past history of DVT and/or pulmonary embolism; iii) Diagnosed hypercoagulable disease (e.g., Protein C and Protein S deficiency, Factor 5 Leiden); iv) Significant renal/hepatic impairment (creatinine clearance \<15mL/min, Child-Pugh score 10-15 (Class C)); v) Restless Legs Syndrome; vi) Current use of contraindicated medication (such as other anticoagulants, antiviral or oral anti-fungal medications); vii) Clinically significant active and/or recent bleeding (e.g., gastrointestinal, intracranial or haematuria); viii) At increased risk of clinically significant bleeding (e.g., significant inherited bleeding disorders, uncontrolled high blood pressure); ix) Other conditions requiring significant medical monitoring while anticoagulated, such as rheumatoid arthritis, type I or type II diabetes, autoimmune diseases; x) Self-reported body mass index (BMI) ≥40kg/m2, except in competitive athletes (defined as a pre-injury Tegner Activity Scale score of 7-10 and/or undertakes strength training/weightlifting two or more times per week); xi) Any known cardiovascular disease (history of stroke, coronary vascular disease); xii) Chronic obstructive pulmonary disease and/or chronic respiratory disease, except for controlled asthma; xiii) Acute infection of the knee or affected limb; xiv) Inflammatory arthropathy/arthritis; xv) knee osteoarthritis in the ACL-injured knee (assessed on acute knee MRI, defined as focal partial thickness cartilage loss or greater (at least ACLOAS grade 2 cartilage lesion2626) plus one or more definite osteophyte (at least ACLOAS grade 2 osteophyte26 xvi) Concurrent immunosuppressive illness (e.g., AIDS, cancer) and/or immunosuppressant usage; xvii) Connective tissue disorders (such as Ehlers-Danlos syndrome); xviii) Current systemic steroid usage; xix) Intravenous drug users and/or substance addiction.