ACL Cross Bracing Protocol: Everything you need to know

Author: Scott Harrison - Senior Physiotherapist, BSc (Exercise and Sports Science), MPhysio

MRI images demonstrating MRI evidence of ACL healing for five participants. ACL, anterior cruciate ligament; ACLOAS, Anterior Cruciate Ligament OsteoArthritis Score.

The ACL Cross Bracing Protocol (CBP) is an evidence-based, non-surgical management strategy designed to facilitate the spontaneous healing of acutely ruptured anterior cruciate ligaments (ACLs). Developed to mitigate surgical risks while maintaining native knee biomechanics, the protocol utilizes specific range-of-motion (ROM) bracing to approximate torn ligament ends and encourage structural tissue continuity.

Key Clinical Outcomes & Evidence

According to recent clinical findings (Filbay et al., 2023), non-surgical management using the Cross Bracing Protocol yields competitive recovery metrics compared to traditional ACL reconstruction (ACLR):

• Structural ACL Healing:90% of select complete ACL tears demonstrate MRI evidence of healing (continuous ligament fibers) at 3 months post-injury.

• Functional Recovery: Participants achieved an average Lysholm Score of 95/100 at 12 months, indicating excellent self-reported knee function. For context, historical post-operative averages range between 85–95/100 (Carey et al., 2009).

• Return to Sport (RTS):79% of participants returned to their pre-injury sports level within 12 months, including 66% of elite/competitive athletes.

• Secondary Joint Injuries: Associated meniscal tears (present in 49% of study cases) often stabilize and become asymptomatic alongside ACL tissue restoration.

• Re-injury Rates: The 12-month re-injury rate (14%) remains congruent with global re-injury averages post-ACLR.

Phase-by-Phase Bracing Timeline

Implementation must occur within 4 weeks post-injury to ensure optimal healing potential. Supervised upper-body and contralateral limb rehabilitation is maintained throughout all phases.

Phase 1: Weeks 1–4

• Locked strictly at 90° flexion (24/7)

• Non-weight bearing

• Maximize ligament approximation; mandatory prophylactic anticoagulants overseen by a physician to prevent Deep Vein Thrombosis (DVT).

Phase 2: Week 5

• Restricted to 90°–60° flexion

• Non-weight bearingInitial controlled ROM introduction; continuous crutch or mobility scooter use

Phase 3: Week 6

• Extended to 90°–45° flexion

• Non-weight bearing

• Incremental extension expansion while guarding healing tissue

Phase 4: Week 7

• Restricted to 30° to full flexion

• Partial weight bearing

• Gradual axial load introduction using crutches; ongoing pharmacological DVT prophylaxis

Phase 5: Week 8

• Restricted to 20° to full flexion

• Partial weight bearing

• Final week of mandatory DVT prophylaxis; preparation for unassisted gait

Phase 6: Week 9

• Restricted to 10° to full flexion

• Full weight bearing

• Transition to unassisted weight-bearing inside the brace

Phase 7: Weeks 10–12

• Full range of motion unlocked

• Full weight bearing

• Functional gait restoration; preparation for brace weaning

Phase 8: Post-Week 12

• Brace removed

• Unrestricted (Criterion-based)

• Transition to high-level functional, neuromuscular, and sports-specific rehabilitation.

Patient Eligibility & Clinical Considerations

Determining candidacy requires a formal clinical assessment, high-resolution MRI review, and physician clearance.

Ideal Candidates & Inclusion Factors:

• Presentation within 16 days of initial injury.

• Confirmed acute full-thickness ACL rupture (isolated or complex).

• Presence of concomitant meniscal (49%), medial collateral ligament (MCL, 50%), or posterolateral corner (PLC, 39%) injuries does not automatically preclude eligibility.

Associated Clinical Risks:

• Vascular: Increased risk of Deep Vein Thrombosis (DVT) due to prolonged immobility (managed via mandatory anticoagulation).

• Musculoskeletal: Rapid quadriceps and hamstring muscle atrophy; risk of joint stiffness or extension/flexion contractures.

• Biomechanical: Secondary overuse injuries on the contralateral limb.

References & Primary Sources

1. Filbay, S. R., et al. (2023).Healing of acute anterior cruciate ligament rupture on MRI and outcomes following non-surgical management with the Cross Bracing Protocol. British Journal of Sports Medicine.

2. Filbay, S., et al. (2022).Spontaneous healing of the ruptured anterior cruciate ligament: Observations from the KANON trial. Osteoarthritis and Cartilage, 30, S21-S22.

3. Carey, J. L., et al. (2009).A systematic review of anterior cruciate ligament reconstruction with autograft compared with allograft. J Bone Joint Surg Am, 91(9), 2242-2250.

4. Ihara, H., & Kawano, T. (2017).Influence of Age on Healing Capacity of Acute Tears of the Anterior Cruciate Ligament Based on Magnetic Resonance Imaging Assessment. J Comput Assist Tomogr, 41(2), 206-211.

5. Jacobi, M., et al. (2016).Healing of the Acutely Injured Anterior Cruciate Ligament: Functional Treatment with the ACL-Jack, a Dynamic Posterior Drawer Brace. Adv Orthop, 2016, 1609067.The ACL Cross Bracing protocol is an non-surgical bracing program that is designed to increase the probability of healing of the anterior cruciate ligament in complete ACL tears (rupture, full thickness tear).

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