Unlock ALL 989 Research Reviews now Learn more

Healing of acute anterior cruciate ligament rupture on MRI and outcomes following non-surgical management with the Cross Bracing Protocol

Review written by Dr Teddy Willsey info

Key Points

  1. After management with the Cross Bracing Protocol (CBP), 90% of patients had signs of anterior cruciate ligament (ACL) healing on the 3-month MRI, compared with 30% in a non-CBP trial.
  2. Increased evidence of healing at the 3-month MRI was significantly associated with better long-term outcomes, with 50% going on to have grade 1 healing with full continuity of the ACL.
  3. The CBP and MRI technique of monitoring healing appears to be a viable alternative to immediate ACL reconstruction. This will likely be a large area of research in the coming years.


Current management strategies for ACL ruptures have been shaped by the belief that the ACL has limited healing capacity. This assumption has been called into question, as conservative management is proving to be a viable treatment option for some, and evidence of ACL healing has been observed via MRI (1,2). From a biological and histological perspective, the ACL tissue has a rich vascular supply, and has been shown to go through normal phases of healing post-injury.

The novel cross bracing protocol (CBP) is a conservative ACL protocol where the knee is immobilized at 90 of flexion for four weeks immediately post injury, and then progressed to full ROM by 10 weeks. The CBP is thought to facilitate healing of the ACL by reducing the gap between the two ends of the ruptured ligament and providing it an opportunity to rebuild its continuity.

The objective of this study was to investigate MRI evidence of ACL healing, patient reported outcomes, and knee laxity in the first 80 participants willing to give the CBP a try.

The ACL tissue has a rich vascular supply and has been shown to go through normal phases of healing post-injury.
Researchers may be able to develop clinical prediction rules for the likelihood of ACL healing within the first three months of injury.


  • 80 patients with acute ACL rupture (< 4 weeks) were recruited over a 5-year period with an average age of 26.

  • Participants chose to participate in the CBP after being informed of all options.

  • The use of cryotherapy and anti- inflammatory medications was discouraged to minimize impairment of the acute inflammatory response.

  • 14 patients who were greater than 1-week post-injury with minimal joint effusion underwent a platelet rich plasma (PRP) injection to encourage hemarthrosis.

  • DVT prophylaxis was initiated on the 11th patient, as 2 of the first 10 patients were diagnosed with below knee DVTs.

  • Exercise Progression: Patients performed cross-education exercises during weeks 0-4. They began weight bearing week 5 and performing isometrics, hip add/abd, leg press, leg extension, hamstring curls, isometrics, calf raises, glute bridges, wall sits, body-weight squats and core activation within their ROM restrictions. Full ROM with full weight bearing (FWB) began at week 10, as they focused on ROM and gait normalization alongside a continued focus of strength. Jog to run progressions began around week 14, with a goal of 90% limb symmetry index (LSI) by week 20 and return to sport (RTS) activities at 6-9 months.



At three month follow up, 90% showed MRI evidence of healing: 50% Anterior Cruciate Ligament Osteoarthritis Score (ACLOAS) grade 1 (continuous thickened ligament and/or high intraligamentous signal) and 40% grade 2 (continuous but thinned/elongated or complete discontinuity). Of the eight patients with grade 3 (non-continuous), six ACLs had attached to the lateral wall and/or PCL. Interestingly, healing grades only changed for five of the 80 participants from three to six months, with four of those five improving from grade 1 to grade 0, and one re-injury.

Participants with grade 1 healing observed on a 3-month MRI reported better outcomes, reduced knee laxity, and a better RTS (92% vs. 62%) compared with grades 2-3. 11 total participants (14%) experienced re-injury. Four (previously grade 1) sustained high energy contact sport injuries (skiing, cycling, rugby, football). The seven remaining reinjuries had all been grade 2-3. Only 1 of 39 patients with meniscal injury had persistent symptoms after the CBP and underwent meniscal surgery.


A flexion contracture was noted in 11 patients (14%), although this was resolved in all patients within three weeks. DVTs were noted in 2 of those first 10 patients before prophylaxis was initiated. The pragmatic patient centered design of this study is a limitation due to its lack of control, however it is also probably more realistic. There were departures from protocol on an individual level as well as re-injuries that occurred before the recommended RTS timeline.


Although beyond the scope of this study, it is possible that certain characteristics of ACL rupture observed on acute MRI may help to predict the likelihood of healing. For example, partial femoral avulsions and displacement of ACL tissue outside of the intercondylar notch were strong predictors of grade 2-3 healing at 3-months. Healing grades remained static for 94% of the population from three to six months, indicating that researchers may be able to develop clinical prediction rules for the likelihood of ACL healing within the first three months of injury.

It would be interesting to see research utilizing the CBP imaging and monitoring techniques to inform an escalation of intervention for the varying grades of healing. For example, emergent ACL repair procedures like the “bridge-enhanced ACL restoration (BEAR)” and “Fertilized ACL” are showing promising results and could be a viable alternative for the CBP grade two group. These techniques utilize biologics as a histological scaffold to augment the healing of the ACL in situ, negating the need for autograft harvesting, implantation, and fixation (3,4).

Many individuals who undergo ACLR experience poor long-term outcomes, reduced activity participation, persistent pain, and early onset of OA. The number of re-injuries and adverse events following ACLR are unacceptably high.

Momentum is building for conservative ACL management, and there appears to be a spectrum of ACL healing that can be determined via MRI at 3-months post injury, or even possibly sooner. Although the quality of life (QOL) impact of the bracing protocol, the 3-month waiting period, and the 50/50 potential for knee instability will be early barriers to CBP implementation in competitive sport, this paper serves as a valuable contribution to the evolving field of ACL research.


Filbay S 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, Published Online First.


  1. Rodriguez, K., Soni, M., Joshi, P. K., Patel, S. C., Shreya, D., Zamora, D. I., Patel, G. S., Grossmann, I., & Sange, I. (2021). Anterior Cruciate Ligament Injury: Conservative Versus Surgical Treatment. Cureus.
  2. Reijman, M., Eggerding, V., van Es, E., van Arkel, E., van den Brand, I., van Linge, J., Zijl, J., Waarsing, E., Bierma-Zeinstra, S., & Meuffels, D. (2021). Early surgical reconstruction versus rehabilitation with elective delayed reconstruction for patients with anterior cruciate ligament rupture: COMPARE randomised controlled trial. BMJ.
  3. Murray, M. M., Fleming, B. C., Badger, G. J., BEAR Trial Team, Freiberger, C., Henderson, R., Barnett, S., Kiapour, A., Ecklund, K., Proffen, B., Sant, N., Kramer, D. E., Micheli, L. J., & Yen, Y. M. (2020). Bridge-Enhanced Anterior Cruciate Ligament Repair Is Not Inferior to Autograft Anterior Cruciate Ligament Reconstruction at 2 Years: Results of a Prospective Randomized Clinical Trial. The American journal of sports medicine.
  4. Lavender, C., Singh, V., Berdis, G., Fravel, W., Lamba, C., & Patel, T. (2021). Anterior Cruciate Ligament (ACL) Reconstruction Augmented With Bone Marrow Concentrate, Demineralized Bone Matrix, Autograft Bone, and a Suture Tape (The Fertilized ACL). Arthroscopy, sports medicine, and rehabilitation.
Healing of acute anterior… By Dr Teddy Willsey