Why Do I Still Have Knee Swelling 6 Weeks After ACL Surgery?
- Emma Glynn
- Jun 17, 2025
- 5 min read
Updated: 2 days ago
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.
What’s a red flag?
Red flags that should be assessed promptly
Fever, chills, or feeling systemically unwell
Increasing redness, warmth, or severe tightness around the knee
Rapid escalation in swelling or pain
Calf swelling or pain (possible DVT)
Sudden loss of knee extension or flexion
True instability or giving way
If any of these are present, early clinical review is recommended.
Why Knee Swelling Might Still Be Hanging Around
If your knee is still swollen six weeks post-op, there are a few common contributors:
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.
Not Enough Movement: Doing too little can also be a problem. Inactivity limits circulation and joint fluid clearance, which may cause swelling to linger.
Poor Quad Activation: If your quadriceps aren’t activating well, your knee lacks muscular support. This can increase joint stress and contribute to swelling.
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).
Not sure if your swelling is normal? If your knee is still swollen and you're not sure whether you're doing too much, too little, or the wrong things entirely - that's exactly what an ACL check-in is for. Emma works with post-op ACL patients in Camberwell and online across Australia. You'll leave with a clear picture of where your recovery is at and what to do next.
3 Things That Can Help Right Now
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.
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.
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.
Not sure whether your current rehab is at the right level? Take Emma's free knee assessment quiz — it takes 60 seconds and tells you where your recovery stands.
When swelling blocks progress (and what clinicians assess)
When effusion persists or limits progression, clinicians typically assess:
Effusion grading
Knee range of motion (especially extension)
Quadriceps and hamstring strength
Movement quality (walking, stairs, squats)
Confidence, fear, and symptom behaviour
Addressing swelling early can prevent delays in later rehab milestones such as running, jumping, and return to sport [4,8].
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
Not sure if what you're experiencing is normal? Take Emma's free 60-second quiz. It's designed for people with hip and knee injuries who aren't sure what's driving their pain or whether their recovery is on track.
Book an ACL Rehab Check-In
At The Hip and Knee Physio, Emma Glynn is a knee physiotherapist in Melbourne with a focus on ACL rehabilitation for active adults.
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.
Can't Find What You're Looking For?
Explore more of our most popular services and guides:
Still can't find what you're looking for?
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.
Comments