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Why Is My Knee Still Swollen 6 Weeks After ACL Surgery?

  • Writer: Emma Glynn
    Emma Glynn
  • Jun 17
  • 4 min read

Updated: Oct 3


A girl after she has injured her ACL in her knee

You’re six weeks post anterior cruciate ligament (ACL) surgery, following your surgeon’s instructions, doing your rehab exercises- and yet, your knee is still swollen. Should you be worried? Is this normal?

The short answer: Some swelling is expected after ACL reconstruction, but persistent swelling may be a sign your knee isn’t tolerating the current load well.


In this blog, I’ll walk through what’s normal, what might be contributing to ongoing swelling, and what can support a smoother recovery.


Already know you need a physiotherapy assessment. Book online below.




What’s Normal After ACL Surgery?

Swelling after ACL reconstruction is part of the healing process. In the first 2–3 weeks, it’s common to have:

  • Moderate swelling around the joint

  • Some fluid near the incision sites

  • Discomfort with movement


By the six-week mark, many people experience reduced swelling as inflammation subsides and movement improves.


According to Shelbourne et al. (2009), prolonged joint effusion is associated with delayed strength gains and slower recovery. That means persistent swelling beyond this point may be worth investigating further.


Why Swelling Might Still Be Hanging Around

If your knee is still swollen six weeks post-op, there are a few common contributors:

  1. Load > Capacity: You may be doing too much, too soon. Even with good intentions, walking further, cycling harder, or squatting deeper than your knee is ready for can lead to ongoing joint effusion.

  2. Not Enough Movement: Doing too little can also be a problem. Inactivity limits circulation and joint fluid clearance, which may cause swelling to linger.

  3. Poor Quad Activation: If your quadriceps aren’t activating well, your knee lacks muscular support. This can increase joint stress and contribute to swelling.

  4. Joint Irritation or Synovitis: In some cases, low-grade synovitis or scar tissue can contribute to persistent swelling. A physiotherapist can assess and adjust your rehab accordingly.

    (Palmieri-Smith et al., 2008).


3 Things That Can Help Right Now

  1. Physio-Led Rehab Plan: A tailored program that targets the quads, hamstrings, and calves at the right level for your current capacity is key. It’s not just about doing more- it’s about doing what your knee can tolerate safely.

  2. Balance Load and Rest: Recovery requires controlled movement. A structured rehab plan can help identify which exercises to progress, which to pause, and how to train without flare-ups.

  3. Manual Therapy and Swelling Support: Techniques like massage, soft tissue release, or taping may assist some individuals, but they’re usually adjuncts- not the main solution.


When Should You Seek Help?

If you’re noticing any of the following, consider getting a professional review:

  • Swelling is worsening or hasn’t improved

  • The knee feels hot, red, or unstable

  • You’re unable to fully bend or straighten your leg

  • You’re avoiding activity due to pain or frustration


Book an ACL Rehab Check-In

At The Hip and Knee Physio in Camberwell, Emma Glynn (APA Titled Musculoskeletal Physiotherapist) works with ACL clients regularly, guiding them through recovery with individualised treatment.


If you’re unsure whether your knee is on track, an ACL post-op check-in can help assess swelling, movement, strength, and provide a personalised rehab plan.



Moving Forward: Your Next Steps

Booking an initial consult is the best way to get clear on your options. You’ll leave with a personalized plan, a clearer understanding of what’s driving your pain, and evidence-based strategies you can use straight away.


If you’re in Melbourne or Camberwell and need experienced hip and knee physiotherapy, book a consultation with APA Titled Hip and Knee Physio - Emma today.



Not sure what’s behind your hip or knee pain?

Take this free, 60-second quiz created by APA Titled Musculoskeletal Physiotherapist Emma Glynn. It’s designed to help you identify the most likely cause of your pain — from fat pad irritation to osteoarthritis — and guide your next step.

👉 Take the quiz now and get tailored insights to move forward with confidence.



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Disclaimer

The content provided on this website is for general information and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. While The Hip and Knee Physio strives to present accurate and up-to-date information, we do not guarantee results or outcomes based on the information provided. Any exercises, strategies, or recommendations featured on this site should not be considered a personalized treatment plan. Always seek the advice of a qualified healthcare provider before starting any exercise program, particularly if you are experiencing pain, injury, or a pre-existing medical condition. Use of this website does not create a physiotherapist–patient relationship. The Hip and Knee Physio accepts no responsibility for any injury or loss arising from reliance on or use of this information. By using this website, you agree to these terms.


References

  • Shelbourne, K. D., Gray, T., & Haro, M. (2009). Incidence of residual knee laxity after anterior cruciate ligament reconstruction. American Journal of Sports Medicine, 37(3), 516–521.

  • Palmieri-Smith, R. M., Thomas, A. C., & Wojtys, E. M. (2008). Maximizing quadriceps strength after ACL reconstruction. Clinics in Sports Medicine, 27(3), 405–424.


 
 
 
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