This is a prospective randomized controlled trial with the purpose to determine if patients undergoing isolated posterior cruciate ligament (PCL) reconstruction, or isolated medial collateral ligament (MCL) reconstruction, or combined PCL, anterior cruciate ligament (ACL), fibular collateral ligament (FCL), posterolateral corner (PLC), and MCL reconstructions (or any combination of multiple ligaments) can safely begin partial controlled weightbearing for the first six weeks after surgery.

Patients will be randomly assigned to one of two rehabilitation protocols for the first six weeks post-surgery:

1. non-weightbearing
2. partial weightbearing

An immobilizer brace in extension will be used from post-operative day 0 through 4 and a dynamic stabilizing posterior knee brace (Ossur) will be used from 5 days through 6 months post-surgery to protect against increased posterior translation forces due to gravity and while weightbearing for patients with PCL reconstructions.

Specific Aims

1. Primary Aim: To determine if there is clinical equivalence in millimeters of posterior tibial translation on posterior stress radiographs at six months post-surgery between patients who are non-weightbearing versus partial controlled weightbearing during the first six weeks of post-surgical rehabilitation.
2. Primary Aim: To determine if there is clinical equivalence in millimeters of valgus and/or varus compartment gapping on stress radiographs at six months post-surgery between patients who are non-weightbearing versus partial controlled weightbearing during the first six weeks of post-surgical rehabilitation.
3. Secondary Aim: To determine if there is a difference in pain, edema, range of motion, gait, and quadriceps strength between groups.

The current standard of care for posterior cruciate ligament reconstruction and multiligament reconstruction is non-weightbearing for the first six weeks after surgery.

Inclusion Criteria:

• ≥ 14 years old, <60
• Reconstruction of PCL alone
• Reconstruction of MCL alone
• Reconstruction of combined multiligament injuries (PCL+ (FCL, PLC, ACL, MCL))
• Reconstruction of multiligament injuries (ACL+MCL)
• Males or females
• Is willing and able to comply with the clinical trial plan and able to understand and sign the Patient Informed Consent Form.

Exclusion Criteria:

• < 14 years old
• >60 years old
• Pregnant
• Revision PCL reconstructions
• Previous or concurrent vascular injury (vascular bypass procedure)
• Associated fractures requiring concurrent surgery
• Concurrent meniscal root or radial repair surgery