The Crucial First Phase of ACL Rehab
Why Nailing Early Rehab is Key to Your ACL Recovery Success
You've had the injury, had the surgery, and now you're facing the rehab mountain.
As a sports physio, I work with people navigating this path every single day. We often focus heavily on the end game – getting back to running, jumping, sport-specific drills, and the eventually, back in the game.
But over years of practice and looking hard at the research, I've become convinced that the most critical phase for your long-term success is the one we sometimes rush through: the very beginning.
Honestly, the outcomes after ACL reconstruction (ACLR) aren't always what we hope for.
Even with brilliant surgery, getting back to your pre-injury sport level isn't a given (around 65-80% manage it recreationally), re-injury rates can be frustratingly high (especially for younger athletes - up to 30% in the first 2 years returning back to sport), performance can take a hit (not back to your best until 2nd season back), and that risk of early knee osteoarthritis is a real concern down the track (most people start to see radiographic changes within 5-10 years).
So, why is that? It's complex, of course, but one area that consistently comes up in both research and my clinical experience is how well (or poorly) the early stage of rehabilitation is managed.
Think of it like building a house.
You wouldn't dream of cutting corners on the foundations, would you?
That initial phase of rehab is the foundation for everything that follows. If you don't get this bit right, you're essentially building on sand, making the whole process harder and potentially limiting how well you recover in the end.
(Quick aside: Don't forget "pre-hab"! If you have the chance before surgery, working on reducing swelling, getting that knee fully straight, and waking up your quads makes a significant positive impact on your recovery afterwards. It's well worth the effort!)
So, What Does "Nailing Early Rehab" Mean in Practice?
From my perspective, blending clinical know-how with the evidence synthesised in Dr Matt Buckthorpe and colleagues seminal paper, truly effective early-stage rehab (this isn't strictly time-based, more about hitting milestones, but often covers the first 4-6 weeks or so) needs a laser focus on six key areas.
1. Taming Pain and Swelling: Seems basic, but it's fundamental. Pain and swelling aren't just annoying; they actively inhibit your muscles (that quad muscle really doesn't like swelling!) and physically block your ability to regain movement. We need to manage this proactively with the usual suspects – ice, compression, elevation – but also gentle, controlled movement. Crucially, you need to learn to monitor it: If your knee puffs up or gets significantly sorer after doing something, that's valuable feedback – you've likely pushed it a bit too hard for now. Listen to those signals!
Practical Tip: We often use a simple 0-10 pain scale. Aim for pain to be consistently low, ideally 0-2/10 specifically in the knee joint during and after your exercises. A bit of discomfort elsewhere (like the graft harvest site) might be okay up to maybe 4/10, but knee joint pain is the key signal.
Practical Tip: Keep an eye on swelling. Your physio might use a 'sweep test', but you can easily track knee circumference yourself with a tape measure around the kneecap. Compare it to the other side, and watch for changes day-to-day. An increase of more than 1cm often suggests you've overdone things a bit.
2.Reclaiming Range of Motion (ROM): Getting your knee bending and straightening again is vital. Getting full knee extension (your leg completely straight) back as soon as possible is absolutely critical. Trust me on this one. Losing even a tiny bit of extension early on can cascade into longer-term issues – altered walking, kneecap pain, even stubborn scar tissue limiting movement (arthrofibrosis). Gentle, consistent exercises (passive and active) need to start almost straight away. Getting the bend (flexion) back is important too, but nailing that extension early is often the game-changer. Hydrotherapy can be brilliant for this once your wounds are safely healed.
Practical Tip: Simple exercises like 'prone hangs' (lying face down on your bed with your leg hanging off the edge, letting gravity gently straighten the knee) are brilliant for extension. For flexion, gentle heel slides (lying on your back, sliding your heel towards your bum) are a staple. Early active movements, even assisted, in the pool can also feel great once wounds are healed.
3. Waking Up the Muscles (Dealing with AMI & Building Strength): This is a massive hurdle. After the trauma of the injury and surgery, your brain often slams the brakes on your quadriceps muscle. We call this Arthrogenic Muscle Inhibition (AMI), or "quad shutdown". Here's the kicker: you cannot properly strengthen a muscle that your brain is actively inhibiting. So, a huge part of early rehab is about overcoming this inhibition before you start thinking about heavy lifting. Strategies I use and we discussed in the paper include:
Neuromuscular Electrical Stimulation (NMES) – basically jump-starting the muscle.
Blood Flow Restriction (BFR) training – clever way to get a muscle-building effect with lighter, safer loads.
Cross-education – working the other leg hard actually sends signals that help the recovering leg. Simple, but effective!
Smart exercise selection – including carefully chosen Open Chain exercises (like knee extensions, maybe in protected ranges to start) and Closed Chain work (like leg presses or squats).
And don't forget the supporting cast! Hamstrings need attention (especially if you had a hamstring graft – think of it like rehabbing a significant hamstring strain), as do your calf muscles, and, critically, your hip and core muscles. A strong neighbourhood supports the knee.
Practical Tip: Check for 'quad lag'. Can you lie on your back and lift your straight leg off the bed without your knee bending or 'lagging'? If you can do 10 reps smoothly, that's a great sign your quad is starting to fire properly.
Practical Tip: We often use tools like NMES (electrical stim) or BFR (blood flow restriction cuffs) early on. These techniques can help stimulate the quad muscle and get strength/size benefits even when you can only tolerate very light loads, reducing stress on the healing joint and graft.
Practical Tip: Early quad exercises often start with isometrics (tensing the muscle without moving the joint, perhaps holding for 5-10 seconds, or longer holds like 45 seconds at comfortable angles like 60-90 degrees of knee bend). Once you can bend the knee comfortably past 90 degrees, very light (1-3kg) knee extensions through the full available range might start. Later in this early phase, we might progress to slightly heavier knee extensions but performed only in a mid-range (e.g., 90 down to 45 degrees) to load the muscle effectively while minimising stress on the kneecap and graft.
Practical Tip: Don't forget the neighbours! Simple exercises like bridges (lying on your back, lifting your hips) target hamstrings and glutes. Clamshells or side-lying leg raises work the hip muscles. Calf raises are important too. Working the other leg hard (e.g., single leg press, hamstring curls) also has a proven 'cross-education' benefit for the operated leg.
4. Mastering Movement Quality (in Everyday Life): How you walk out of the clinic today genuinely impacts how you'll run in a few months. Compensatory movements – limping, shifting your weight away from the operated leg when standing up or doing a simple squat – become ingrained habits incredibly quickly. Early rehab must include retraining good quality, basic movement. This means working on your walking pattern (right from using crutches correctly), balance drills, and fundamental exercises like controlled bodyweight squats, often using feedback (like a mirror or my watchful eye!). Hydrotherapy again offers a great low-load environment to practice. Coming off crutches shouldn't just be about time passed; it needs to be based on hitting criteria – like that full knee extension, minimal swelling, good quad control, and walking reasonably well without them.
Practical Tip: Before ditching crutches, we need to see certain things: minimal pain/swelling, full active knee extension (no lag!), and a reasonably 'normal' looking walking pattern when assessed (ideally on a treadmill). Don't rush this step!
Practical Tip: We'll look at basic movements like a simple bodyweight squat. Can you squat to around 90 degrees without your weight dramatically shifting away from the operated leg? We often aim for less than a 20% difference in loading between legs, even this early. We might use visual feedback (mirrors) or simple scales to help retrain this symmetry.
5. The Head Game & Your Support Crew: Let's be honest, an ACL injury can be as much a mental battle as a physical one. Dealing with the shock, fear, frustration, and feeling disconnected is a massive part of the journey. Good rehab absolutely has to acknowledge this. Things that help are:
Understanding what's happened and the road ahead.
Having solid emotional support – whether that's your physio, teammates, family, or friends. It's okay to talk about the tough stuff.
Building a trusting relationship and having open communication with your rehab team.
Getting practical help when you need it (lifts, help around the house). Asking for help isn't weakness; it's smart recovery.
6. Preserving Overall Fitness: While your knee needs careful management, don't let your general fitness completely disappear. The rehab process is long; use the time wisely. This means:
Safe cardio options early on often include an arm bike (ergometer) or stationary cycling once your knee bend allows. Pool running or swimming (avoiding whip kick initially) can be added once wounds heal.
For strength, focus on upper body work and exercises for your non-operated leg (like single leg press, extensions, curls, calf raises).
Thinking about nutrition to help manage your body composition during a less active period. It's not the absolute top priority in week one, but integrating this early helps maintain a baseline, prevents unnecessary deconditioning, and can be a real psychological win.
Bringing It All Together – The Physio Bit
So, how do we make this happen? From my side, structuring effective early rehab involves:
A Holistic Approach: Looking at you as a whole person, not just a knee, and addressing all six areas.
Smart Prioritisation: Knowing what needs the most focus when (e.g., often pain, swelling, and extension ROM are top priorities right at the start).
Individualisation: No two ACL recoveries are identical. Your programme must be tailored to your surgery (graft type matters, as do any extra repairs like meniscus work), your goals, and your life.
Consistency is King: Little and often is usually the mantra. Daily exercises, even simple ones, make a huge difference.
Constant Monitoring & Adjusting: Regularly checking your pain, swelling (I’ll often show my patients how to do the Sweep Test so that they can track their own response to exercise), ROM, and crucially, how your knee responds to the exercises and activities you do. We adjust the plan based on this feedback.
Criterion-Based Progression: You move to the next stage when you demonstrate you're ready by hitting specific targets (like those mentioned for pain, swelling, ROM, quad activation, walking well), not just because the calendar says it's week 6.
The Bottom Line…
Please don't underestimate these crucial first few weeks after ACL surgery. This isn't just downtime; it's arguably the most important active phase for setting yourself up for success. By diligently working on managing pain and swelling, regaining movement, waking up those key muscles, relearning good movement patterns, looking after your mental well-being, and preserving fitness, you are laying the strongest possible foundation for the rest of your recovery journey. Get the start right, and you give yourself the very best shot at getting back to doing what you love, safely and confidently.
Disclaimer: I'm one of the co-authors of the scientific paper this post is based on. We poured a huge amount of collective experience and research analysis into it because we genuinely believe optimising this early phase can make a massive difference.
Reference:
Buckthorpe M, Gokeler A, Herrington L, Hughes M, Grassi A, Wadey R, Patterson S, Compagnin A, La Rosa G, Della Villa F. Optimising the Early-Stage Rehabilitation Process Post-ACL Reconstruction. Sports Med. 2024 Jan;54(1):49-72. doi: 10.1007/s40279-023-01934-w. Epub 2023 Oct 3. PMID: 37787846.
Link to abstract with supplementary videos at the end of the article here