BOOK NOW

ACL Prehab

Book now

ACL Prehab

Book now

ACL prehab: why squats and lunges matter (science-backed, patient-friendly)

What “ACL prehab” actually means

ACL prehab is structured strength and neuromuscular training done after ACL injury and before a decision point (surgery vs non-surgical management, or before reconstruction if surgery is planned). The goal is to:

    • reduce pain and swelling

    • restore range of motion

    • rebuild strength (especially quadriceps)

    • improve control and confidence

    • improve function for day-to-day life and sport

In other words: prehab is about changing the knee you have today, not just waiting for time to pass.

Important context: it’s rarely “just the ACL”

An ACL injury is often part of a bigger knee injury. It’s common to see associated damage such as:

    • meniscal tears

    • cartilage/chondral injury

    • bone bruising and general joint irritation

That matters because these structures can influence pain, swelling, locking/catching symptoms, and longer-term knee health.

A useful reminder from the literature is that concomitant meniscal injury is frequently reported alongside ACL injury (commonly cited ranges around ~50–60% in some cohorts).

 

Myth-buster

 

Clicks, pops and grinding don’t automatically mean “damage”


Knee noises (crepitus/clicking) can be alarming, but the research doesn’t support the idea that noise alone equals harm.
A recent systematic review and meta-analysis on “noisy knees” evaluates how common knee crepitus is and how it relates to structural findings.


Large cohort work also reports that knee crepitus is not necessarily linked with progression to major outcomes like total knee replacement.


Clinically, this is why we focus less on the noise itself and more on the pattern of symptoms: swelling/effusion, true locking/catching, repeated giving-way, and whether pain/function are trending better or worse over time.

Why squats and lunges are central (not optional)

Squats and lunges (and their progressions) are “closed-chain” strength patterns that load the whole lower limb. They’re central in ACL rehab/prehab because they train the exact qualities most people lose after injury:

    • Quadriceps strength (often the biggest limiter)

    • Hip and trunk control (key for knee alignment)

    • Single-leg capacity (stairs, walking speed, running, change of direction)

    • Tolerance to load (your knee coping with real-life forces)

They’re also easy to scale: you can make them lighter/heavier, shallower/deeper, slower/faster, and more/less single-leg.

 

A quick “how to dose it” safety guide (so you don’t flare the knee)

 

Prehab should feel like training, not punishment. Two simple rules that keep most people on track:

  • Pain and swelling guide progression: if pain is ramping up during the session, or you wake up the next day with more than trace effusion/swelling, scale back (reduce depth, slow tempo, add support, or drop a step).

  • Don’t progress through ongoing effusion: some ACL rehab guidance recommends not progressing exercise when joint effusion is above a mild threshold (for example, >1+ effusion), and to reduce activity if effusion appears or increases.

When to get checked

 

Most knee symptoms after ACL injury are manageable with the right plan. But don’t just “push through” if you have any of the following:

  • True locking (knee gets stuck and you can’t straighten or bend it)

  • Repeated giving-way episodes (especially if they’re increasing)

  • Rapidly increasing swelling/effusion or a sudden big change in swelling

  • Inability to fully straighten the knee that isn’t improving

  • Calf swelling/redness/warmth, chest pain, or shortness of breath (urgent medical review)

  • Fever, feeling unwell, or night pain that’s getting worse

If any of these are happening, get assessed by an appropriate clinician.

 

Who this isn’t for (yet)

 

Squats and lunges are brilliant tools, but timing matters. If your knee is in a very acute flare (significant swelling/effusion, severe pain, you can’t weight-bear properly, or you’ve recently had a big giving-way episode), the first step is usually:

  • Swelling control

  • Range of motion work

  • Early muscle activation (often isometrics)

Then you build back into squat/lunge patterns as the knee settles and tolerates load.

What the research supports (and why it matters)

1) Early progressive exercise improves function after ACL injury (Eitzen 2010)

Eitzen et al. (2010) is an older paper, but it’s basically “prehab” in modern language: a short, progressive exercise therapy programme early after ACL injury produced meaningful improvements in knee function.

Why that matters: it supports the idea that early, structured rehab can improve symptoms and performance quickly—so you’re not stuck in a “rest and wait” loop.

2) Rehab-first approaches can work well (KANON and COMPARE)

Two landmark studies often referenced in ACL decision-making are KANON and COMPARE. The big message is that a structured rehab-first pathway—with surgery reserved for those who still have instability or can’t reach their goals—can produce similar patient-reported outcomes for many people compared with early reconstruction.

Why that matters: it reframes the decision. For a lot of patients, the first best step is not “surgery now,” it’s high-quality rehab now, then decide.

3) Prehab is associated with better outcomes if surgery happens (Failla 2016)

Failla et al. (2016) compared outcomes with and without prehab and reported that prehab is associated with better post-operative outcomes.

Why that matters: even if reconstruction is the plan, prehab still has a payoff. A stronger, better-controlled knee tends to be easier to rehabilitate.

 

3b) A systematic review reports benefits of prehabilitation (PLOS ONE 2020)
 

A systematic review in PLOS ONE reports that “exercises have a positive impact on pre-operative and postoperative functional performance” and that “prehabilitation” shows “superiority in terms of self-reported knee function” at both three months and two years after ACL reconstruction.

4) Knee osteoarthritis risk is higher after ACL injury (but it’s manageable)

It’s well established that ACL injury (especially when combined with meniscus/cartilage injury) increases the risk of developing post-traumatic knee osteoarthritis (OA) over time.

Some reviews specifically look at OA rates around the 10-year mark after ACL injury/reconstruction and report wide ranges depending on definitions and injury combinations.

Why that matters: this is exactly why prehab/rehab matters. You can’t change the fact the knee has been injured—but you can influence symptoms, function, strength, and long-term capacity.

5) Arthritis does not mean “no exercise” — it usually means “more targeted exercise”

A common fear is: “If I’m at risk of arthritis, should I stop loading the knee?”

For most people, the answer is the opposite. Exercise therapy is recommended as a first-line treatment for knee OA in major guidance, because it improves pain and function.

Why that matters: strength work (including squat/lunge patterns, appropriately dosed) is often part of the long-term knee health plan.

6) Supervision matters: better outcomes than home exercise alone 

There’s evidence in knee rehab that supervised rehabilitation can outperform unsupervised/home-based rehab for outcomes like strength, neuromuscular control, and patient-reported function.

Why that matters: ACL prehab isn’t just “do these exercises.” It’s coaching, progression, and decision-making.

The science behind why squats and lunges help an ACL-injured knee

1) They rebuild quadriceps strength (a key predictor of function)

After ACL injury, the quadriceps often “switch off” (inhibition), and strength drops quickly. Squat and lunge patterns let you progressively load the quads while also training hip control.

Practical meaning: stronger quads usually = better stairs, better walking tolerance, better confidence, and better readiness for higher-level rehab.

2) They train control under load (not just strength)

A lot of “giving way” isn’t only about the ligament—it’s about timing, coordination, and control under load. Squats and lunges are ideal for coaching:

    • knee tracking (avoiding uncontrolled collapse)

    • pelvic control

    • trunk position

    • controlled deceleration (especially the lowering phase)

Practical meaning: you’re building a knee that can handle real movement, not just a knee that can do isolated exercises.

3) They progress naturally from early rehab to return-to-sport

You can start with supported, shallow ranges and progress to deeper, heavier, and more sport-specific variations.

Practical meaning: the same exercise “family” can take you from early-stage confidence building to late-stage strength and performance.

Why regular follow-ups matter (and why DIY rehab often stalls)

A good prehab plan isn’t a static list—it’s a progression. Early after ACL injury, things change week to week: pain, swelling, range, confidence, and how well you tolerate load.

That’s why we typically recommend:

    • Weekly sessions early on (to coach technique, manage symptoms, and progress load safely)

    • then no more than 2 weeks between reviews while you’re still building strength and control

This isn’t about “needing someone to watch you exercise.” It’s about progressing the right variables at the right time:

    • load (how heavy)

    • range (how deep)

    • tempo (how controlled)

    • single-leg bias (how much demand)

    • complexity (balance, direction change, speed)

A simple squat/lunge progression (prehab-friendly)

Use pain and swelling as your guide. The knee should feel worked, not punished.

  1. Sit-to-stand / box squat (control, symmetry)
  2. Goblet squat (load + depth as tolerated)
  3. Split squat (introduce single-leg bias)
  4. Reverse lunge (often better tolerated than forward lunge)
  5. RFESS (rear-foot elevated split squat) (high quad demand)
  6. Step-downs and step-ups (real-world strength)

  1. Coaching cues that matter:

    • slow lower (3–4 seconds)

    • keep the foot “tripod” (big toe, little toe, heel)

    • control knee collapse (don’t chase perfect—chase controlled)

Who should consider ACL prehab?

    • Anyone with a recent ACL injury who is unsure about surgery

    • Anyone planning reconstruction (to go in stronger)

    • Anyone with instability episodes who needs better strength and control

The bottom line

The best evidence-based starting point after ACL injury is rarely rest. It’s progressive rehab.

Squats and lunges aren’t trendy exercises—they’re efficient tools to rebuild the strength and control that make the knee feel stable again. And the bigger studies (KANON/COMPARE) support what clinicians see every day: for many people, a rehab-first approach can deliver outcomes comparable to early surgery, with surgery reserved for those who truly need it.

 

If you want help, we can guide you through it

 

If you want a clear, safe plan for your knee (and a step-by-step progression for squats and lunges based on your symptoms), book an assessment with our team.

References

    • Eitzen et al. (2010). A Progressive 5-Week Exercise Therapy Program Leads to Significant Improvement in Knee Function Early After Anterior Cruciate Ligament Injury.

    • Failla et al. (2016). Does Extended Preoperative Rehabilitation Influence Outcomes 2 Years After ACL Reconstruction? (prehab vs no-prehab comparison).

    • Frobell et al. (KANON trial). Treatment for acute anterior cruciate ligament tear: structured rehabilitation plus early ACL reconstruction versus structured rehabilitation and optional delayed ACL reconstruction.

    • COMPARE trial. Early ACL reconstruction versus rehabilitation with optional delayed reconstruction: comparison of outcomes.

    • Keyhani S, Esmailiejah AA, Mirhoseini MS, Hosseininejad S-M, Ghanbari N. (2019). The Prevalence, Zone, and Type of the Meniscus Tear in Patients with Anterior Cruciate Ligament (ACL) Injury; Does Delayed ACL Reconstruction Affects the Meniscal Injury? Archives of Bone and Joint Surgery. https://pmc.ncbi.nlm.nih.gov/articles/PMC7358246/

    • Rhim HC, Lee JH, Lee SJ, Jeon JS, Kim G, Lee KY, Jang K-M. (2021). Supervised Rehabilitation May Lead to Better Outcome than Home-Based Rehabilitation Up to 1 Year after Anterior Cruciate Ligament Reconstruction. Medicina (Kaunas). https://pmc.ncbi.nlm.nih.gov/articles/PMC7824668/
    • Escamilla RF, et al. (2012). ACL strain and tensile forces for weight bearing and non-weight-bearing exercises after ACL reconstruction: a guide to exercise selection. Journal of Orthopaedic & Sports Physical Therapy.
    • Fukuda TY, et al. (2013). (Closed kinetic chain / weightbearing exercise rationale).
    • “Noisy knees” systematic review: https://pubmed.ncbi.nlm.nih.gov/39375004/
    • Cohort paper on crepitus + outcomes: https://pubmed.ncbi.nlm.nih.gov/30292656/

Book now
Book Now