To date, the use of the quadriceps tendon as an autograft option in primary paediatric Anterior Cruciate Ligament (ACL) reconstruction has not been well studied. The 2018 International Olympic Committee (IOC) Consensus Statement now outlines the quadriceps tendon as a possible autograft option. However, no Randomised Control Trial (RCT) has examined the efficacy of the quadriceps tendon autograft in primary paediatric ACL reconstruction compared to the historical "gold-standard" soft-tissue hamstring autograft in this population. In light of its evidence for favourable outcomes in the adult population, and the (albeit limited) evidence showing safety and promise in the paediatric population, clinical equipoise exists for assessing its impact on outcomes in paediatric patients at the index surgery. This is a parallel, international, multi-centre, blinded randomized controlled trial of 352 skeletally-immature (at the time of injury) patients (ages 10-18 years, inclusive) undergoing primary ACL reconstruction to compare the effect of autograft tendon choice (i.e. hamstring versus soft-tissue quadriceps) on the rates of ACL graft failure, return-to-sport, knee function, pain, health-related quality of life and health utility, psychological factors, range of motion and stability, and any other adverse events at 24 months.

Inclusion Criteria

1. Patients aged 10-18 years.
2. History, physical exam, and magnetic resonance imaging (MRI) or arthroscopic image confirmation of ACL insufficiency.
3. Suitable for anatomic, single-bundle arthroscopic-assisted ACL reconstruction.
4. X-ray or MRI evidence of skeletal immaturity (i.e., open physes) based on imaging that is closest to the time of injury (and correlated with standard bone age left hand posteroanterior (PA) radiographs).
5. Patient involved in sport (competitive and/or recreational level) prior to injury.
6. Patient and parent/guardian speak, read, and understand the language of the clinical site.
7. Patient and parent/guardian provide informed consent and/or assent.

Exclusion Criteria

1. Evidence (i.e. radiographic and/or arthroscopic) of International Cartilage Repair Society (ICRS) Cartilage Lesion Classification System Grade 2 (i.e., lesions extending down to 50% of the cartilage depth) and higher osteoarthritis that is symptomatic, requiring treatment other than debridement or microfracture.
2. Tibial eminence/spine fractures treated surgically.
3. Concomitant collateral, posterior cruciate, and/or cartilage pathology requiring surgical reconstruction and/or advanced restoration techniques (i.e., osteochondral allograft or autograft transfer, matrix-induced autologous chondrocyte implantation, particulate juvenile articular cartilage allograft transplantation).
4. Previous ACL reconstruction in the affected knee or contralateral knee.
5. Previous distal femur and/or proximal tibial/fibular physeal injury in the affected knee or contralateral knee.
6. Allograft or allograft-augmentation, or synthetic augmentation of the ACL reconstruction.
7. Biological-augmentation of the ACL reconstruction (i.e. platelet-rich-plasma, fibrin clot, reinforced bioinductive implants, etc.).
8. ACL reconstruction utilizing synthetic grafts.
9. Primary ACL repair.
10. Patient diagnosed with inflammatory arthropathy.
11. Significant medical co-morbidities (requiring daily assistance for activities of daily living).
12. Patient, parent/guardian, and/or clinical investigator believe the patient will have difficulty maintaining follow-up.

Autograft donation incisions will be covered with adhesive bandages for clinical outcome assessment by the attending physician. The assessor will perform a physical assessment of the patient's knees, including range of motion and laxity.