Anatomic ACL reconstruction using a four-strand autologous hamstring graft. If the diameter of the graft is found to be less than 7.5mm, semitendinosus will be tripled (5 strand graft) providing a greater graft diameter. Femoral tunnels will be drilled using an anteromedial portal technique, with femoral fixation provided by an Endobutton or equivalent. Tibial fixation will be provided by interference screw.

The MARS Activity Rating Scale is a four-item activity rating scale. The patient is asked to rate how often they were able to perform each activity (e.g. running, cutting, decelerating, and pivoting) in their most healthy and active state. The patient is provided with five categories of frequency of each functional activity, ranging from less than one time in a month to four or more times in a week. One point is allocated for each category of frequency and a maximum score of 16 points can be awarded. The MARS has demonstrated excellent test-retest reliability and construct validity in patients with disorders of the knee.

The International Knee Documentation Committee Subjective Knee Form (IKDC) is a knee-specific functional outcome that consists of 18-items about symptoms (7 items), sports activities (10 items) and function (1 item). Likert scales, a dichotomized item and 11 point rating scales make up the response options, and total score ranges from 0 (total limitation) and 100 (no limitations). The IKDC has shown test-retest reliability and good construct validity in patients with issues at the knee.

MRI will be performed only on patients recruited from the lead site at the Fowler Kennedy Sport Medicine Clinic (n=196). Similar to the imaging protocol used at the two-year visit, patients will undergo bilateral 3 Tesla MRI on a Siemens Magneton Trio magnet, and a 15-channel Siemens PRISMA knee coil at the 10-year visit. Longer T1rho and T2 relaxation times have shown to be associated with worsening cartilage quality. These changes can also be seen prior to the development of radiographic changes of OA, therefore, MRI can be used as a method for early detection of degenerative changes. The high incidence of arthritic changes observable at the 10 year time point using MRI (compared to plain radiographs), justifies the use of MRI in the subgroup of patients at the lead site.

The ACL-QOL has five domains that query physical symptoms, occupational concerns, recreational activities, lifestyle, and social and emotional aspects.

Each item has one 100 mm visual analogue scale response option, with labeled anchors at 0 mm (e.g., extremely difficult) and 100 mm (e.g., not difficult at all). Scores are calculated by converting the average of each of the five domain scores to a total average score out of 100% where 100% represents the best possible score. The ACL-QOL has demonstrated validity in patients with ACL injury and responsiveness to change in patients following ACLR.

Four-item questionnaire that asks patients to report the amount of pain they experience throughout the day (morning, afternoon, evening) and with activity. Each item response is a visual analog scale ranging from 0 (no pain) to 10 (as bad as it can be). The total score is a sum of the four responses to a maximum score of 40. The P4 has demonstrated good test-retest reliability and the ability to detect changes in pain intensity in patients with muscle and joint injuries. Because men and women may experience and report pain differently, we have included the Gender Role Expectation of Pain questionnaire to examine its association with pain and quality of life reporting in this study.

As previously described, clinical failure is defined as a composite of symptomatic instability requiring revision ACL surgery, or symptomatic instability with positive pivot shift, or asymmetrical pivot shift greater than the contralateral side.

Range of motion (ROM) measurement will include passive knee extension and active-assisted knee flexion. For passive knee extension, the patient is seated with legs extended on a table, heel propped so that the calf and upper thigh clear the treatment table. We will instruct the patient to relax both quadriceps and hamstrings to assure passive measurement. For active assisted knee flexion, the patient is seated with both legs extended on a table. We will instruct them to perform active-assisted knee flexion by placing one hand under their thigh to initiate flexion and then clasp both hands just below the tibial tuberosity. We will measure flexion and extension in degrees using a goniometer. For both measurements, we will centre the fulcrum of the goniometer over the lateral epicondyle of the femur. We will then align the stationary arm of the goniometer with the greater trochanter of the femur and the moving arm with the lateral malleolus at the ankle.

We will record adverse events including painful hardware, graft rupture, and reasons for re-operation (e.g., painful knee joint, meniscal injuries, ACLR revision, contralateral ACLR, etc.). Given the significance of these types of events, we expect excellent recall.