Inclusion Criteria:

1. Male and female military personnel and civilians with a MLKI (defined as a complete grade III injury of two or more ligaments)
2. Between the ages of 16 and 55
3. Must present to the orthopaedic surgeon in time to undergo definitive surgery within 6 weeks of injury if randomized to the early surgery group
4. Subjects with a MLKI that present to orthopaedic surgery at a time that precludes randomization to early surgery or have an injury that precludes randomizing the timing of surgery (such as a vascular injury) as well as those that refuse randomization to the timing of surgery will be eligible to participate in the study for Aim 2 which randomizes subjects to only early vs. delayed rehabilitation.

Exclusion Criteria:

1. Have a history of prior knee ligament surgery of the involved knee:
2. Have a torn or avulsed patellar or quadriceps tendon;
3. Have a periarticular or long bone fracture that is anticipated to preclude weight bearing after surgery;
4. Require use of an external fixator to maintain reduction of the knee or soft tissue/open wound management for greater than 10 days;
5. Are unable to WB on the contralateral uninjured leg;
6. Have a traumatic brain injury (TBI) that limits their ability to participate in their post-operative care or any condition that would preclude the ability to comply with post-operative guidelines;
7. Skin or soft tissue injury that precludes early surgery and/or early rehabilitation;
8. Surgical procedure that precludes early WB & ROM (i.e. surgery for extensor mechanism rupture or avulsion, vascular graft surgery).
9. Have multiple trauma that limits ability to participate in early rehabilitation;
10. Have a vascular injury that dictates the timing of surgery;
11. Have multiple trauma that precludes surgery within 6 weeks of injury
12. Have vascular surgery that precludes early rehabilitation;
13. Have a skin or soft tissue injury that precludes early weightbearing or range of motion.