The Knee - ACL Injuries Part Two
Diagnosis, Treatment and Rehab
Not every ACL tear needs surgery. Growing evidence shows that, for many people, well-guided rehab can match surgical outcomes. Here's how ACL injuries are graded and assessed, and the treatment conversation you should be having with your physio.
Before we get into management, it's worth understanding the different grades of ACL injury — because this genuinely shapes the decisions ahead of you.
Grade 1, 2 or 3 — how bad is it really?
Contrary to popular belief, not every ACL injury is a complete tear. As we covered in Part One, the ACL can be strained, partially torn, or completely ruptured — Grade 1, Grade 2 and Grade 3 respectively.
- Grade 1: the fibres are stretched but not torn. There may be some swelling and tenderness, but the knee is structurally stable and shouldn't give way with activity.
- Grade 2: some, but not all, fibres are torn. Expect more swelling and tenderness, some loss of range of movement, and occasional feelings of instability.
- Grade 3: the ligament is completely ruptured, often with associated injuries. Swelling is usually large and rapid (within about 2 hours), with loss of range of movement and a knee that gives way, especially with rotation. Interestingly, once the initial shock passes, the pain reported is often much less than you'd expect given the severity.
How we assess an ACL injury
Early, thorough assessment matters — even if the injury feels minor. A good physiotherapist will ask a lot of questions about the injury itself. A great one will also ask what you love doing, and what your goals are.
Most of the time, the history alone tells us whether the ACL is involved, and points us toward any
other structures that may have been affected.
From there, a structured physical assessment — range of motion, ability to weight bear, muscle strength and activation, degree of swelling, plus some specific ligament tests — confirms the clinical picture.
In most cases, medical imaging is recommended. MRI is the gold standard for assessing the ACL and can help determine the grade of tear, while plain x-rays help rule out fractures, which sometimes accompany a significant knee injury (and can change the whole management plan).
Surgery isn't automatic — get the full picture
If the first thing you're told about an ACL injury is “we need to get you in to see a surgeon”, it's worth getting a second opinion. Your assessment findings, imaging results and treatment options should all be explained clearly enough for you to make an informed decision.
Surgery for complete ruptures — particularly in younger, athletic populations — remains the most common approach. But there's a growing body of evidence supporting non-surgical management too, especially for incomplete ruptures or where there's no history of mechanical instability. When you look at pain, function, return to sport, quality of life and the long-term risk of knee osteoarthritis, the outcomes between surgical and conservative approaches are strikingly similar.
The Cross Bracing Protocol
For carefully selected complete ACL ruptures, there's now a specific non-surgical pathway with genuinely promising results — the Cross Bracing Protocol (CBP), developed in Australia by Dr Mervyn Cross and Dr Tom Cross. The idea is to brace the injured knee in a position that brings the torn ends of the ligament close together, giving it a real chance to heal itself, much like immobilising a fracture so the bone can knit back together.
Who's actually eligible?
CBP isn't for everyone, and eligibility is only confirmed after a full physiotherapy assessment, MRI review and medical work-up. Factors that improve the chances of a good outcome include:
- Timing — ideally braced within 4 to 10 days of injury, with a hard cutoff at around 21 days. After this window, the torn ends of the ligament start to retract and close over, and bracing is no longer effective.
- Mechanism of injury — slower-velocity injuries (a twist coming off a ski lift, for example) tend to do better than high-speed, high-impact mechanisms, which more often involve additional damage.
- Early presentation — good function immediately after the injury and minimal early swelling are both encouraging signs.
- MRI findings — a small gap between the torn ends (ideally under 6mm), an intact attachment at the femur, a tear in the upper third of the ligament, minimal displacement of the fibres, and an intact synovial envelope around the ligament.
- Practical factors — occupation, home support and your ability to manage strict weight-bearing restrictions all matter too. This is never a decision made on imaging alone.
It's just as important to know what rules CBP out — this includes a significant risk of blood clots, some complex combined ligament injuries, and simply presenting outside the eligibility window.
When do the scans happen?
An MRI is essential before bracing begins, to confirm the diagnosis and check the injury against the eligibility factors above. A second MRI follows around the 12-week mark (or at the end of the bracing period), alongside a full clinical reassessment, to check for evidence of healing.
What does the bracing actually involve?
The original protocol runs for 12 weeks, though many clinics now use shorter 6 or 8-week versions depending on the specific injury. In the full 12-week version:
- Weeks 1–4: the knee is locked at 90 degrees of flexion, 24/7, and completely non-weight bearing (crutches or a mobility scooter are needed, since the knee can't straighten enough to walk normally).
- Weeks 5–6: the brace is gradually opened to allow more movement.
- Weeks 7–8: partial weight-bearing begins as the brace opens further.
- Week 9 onward: full weight-bearing resumes, with the brace progressively opening to full range of motion by week 12.
Because of the extended period of reduced mobility, blood-thinning medication is typically required during the early weeks to help manage the risk of blood clots, overseen by a sports doctor.
And the rehab timeframes?
Rehab doesn't wait for the brace to come off — it runs throughout the entire bracing period, targeting the injured leg, the uninjured leg and the upper body to limit muscle loss and keep you as capable as possible. Once the brace comes off, rehab continues in a fairly familiar progression: strength, control, and a graded return to sport.
In published outcomes, a good proportion of carefully selected patients showed MRI evidence of ACL healing at around 3 months, and most who met the eligibility criteria returned to their pre-injury sport within about 12 months — with re-injury rates broadly similar to what's reported after surgery.
The take-home on CBP
This is a genuinely exciting development in ACL care, but it isn't a do-it-yourself option, and it's very time-sensitive. If you think you've torn your ACL, getting assessed within days — not weeks — keeps every option on the table, including this one. Talk to your physio as early as possible so you don't miss the window.
If the CBP is out, what does rehab involve?
For a Grade 1 tear, rehab might be as short as 3 to 6 weeks, depending on any underlying risk factors that need correcting. The more significant the injury, the longer the road — surgical repairs typically need 9 to 12 months of rehab before a safe return to full-contact sport.
Rehab is so much more than stretching and strengthening.
It's about retraining the neuromuscular and biomechanical systems we talked about in Part One — strengthening key muscle groups, addressing modifiable risk factors (more in Part Three), tailored exercise prescription, a graded return to sport, and a lot of education along the way. Our clinical classes, including our GLA:D program, are built around exactly this kind of structured, progressive knee rehab.
The take-home
If you've tweaked your knee — even a little — you won't know if you've strained your ACL until it's assessed. A Grade 1 strain significantly raises your risk of a bigger ACL injury down the track, so it's worth heeding the warning: get it checked and do the rehab. It'll save you time, money and missed sport later on.
And know your options. Healthcare is about informed decision-making — surgery for an ACL injury should never feel like a given. Get all the facts, take time to consider your situation, and don't feel pressured either way.
ACL Injuries
Frequently Asked Questions
Ready to get on top of your symptoms?
At Movement for Life Physiotherapy, our team across Coconut Grove and Rosebery can assess your knee and diagnose an ACL injury. Direct referral for further investigations and a network of ACL specialist doctors will help you build a personalised, progressive recovery program to help you get stronger, move better, and back to activity sooner.
Get in touch with our team to book an assessment, and let's build a plan that keeps you strong, active, and pain-free today and into the future.
Give us a call now or click on BOOK AN APPOINTMENT to book online.
This article is general information only and does not replace individual clinical assessment. If you're experiencing joint or muscle pain, book an appointment with one of our physiotherapists for a tailored assessment and treatment plan.
Sources
- Arundale, A.J.H., Bizzini, M., Giordano, A., et al. (2018). Physical Therapy Evaluation and Treatment After Anterior Cruciate Ligament Reconstruction: Clinical Practice Guidelines. Journal of Orthopaedic & Sports Physical Therapy, 48(9), A1–A47.
- Dargo, L., Robinson, K.J. and Games, K.E. (2017). Prevention of Knee and Anterior Cruciate Ligament Injuries Through the Use of Neuromuscular and Proprioceptive Training. Journal of Athletic Training, 52(12), 1171–1172.
- Noyes, F.R. and Barber-Westin, S.D. (2021). ACL Injury Prevention Training Programs: The Injury Epidemic and Prevention Approaches. In: ACL Injuries in the Female Athlete. Springer.
- Filbay, S.R., Dowsett, M., Jomaa, M.C., Rooney, J., Sabharwal, R., Lucas, P., 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, 57(23), 1490–1497.
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