Post-ACL Surgery: Knee Swelling and Pain Issues

Post-operative knee effusion following anterior cruciate ligament (ACL) surgery?

Hello, doctor.
I underwent anterior cruciate ligament reconstruction and partial meniscus repair on October 1st last year, and it has been 9 months since the surgery.
MRI scans taken at the 3-month and 6-month follow-ups showed that the ligament is intact and healing well, but there was a significant amount of effusion, so the doctor advised me to apply ice frequently.

Currently, when lying flat, I cannot fully extend my injured knee (the pain varies from intense to manageable, but I still cannot press it completely against the bed).
When sitting, I can sometimes kick my leg straight, but other times I cannot.
Additionally, my knee occasionally makes a cracking sound when standing straight, but it is not painful.

However, two weeks ago, due to persistent swelling in my knee (despite regular icing), the doctor aspirated approximately 20cc of fluid during my follow-up visit and injected sodium hyaluronate.
The fluid that was aspirated was not clear but had a reddish tint, though it was not bright red like blood.
After the aspiration, the sensation in my knee improved significantly, and I was able to apply pressure to it.
The doctor advised me to refrain from exercising and to return for a follow-up in two weeks.
I showed the MRI to my physical therapist, who assessed that there is fluid accumulation in the posterior-lateral aspect of my knee.
He is currently using shockwave therapy combined with acupuncture and manual therapy to disperse the fluid and bruising.
Two days ago, during my follow-up, the doctor aspirated another 10cc of fluid (which was also reddish).
This time, the sensation after aspiration was not as pronounced as the last time, and I sometimes experience sudden pain (on the lateral side of the knee) after sitting for a while; this varies in intensity.
Additionally, when lying flat to sleep, I can press my knee down with less pain, but upon waking, both the range of motion and pain are worse than before sleeping.
However, moving around after getting up helps alleviate the discomfort.
I would like to ask:
1.
What could be causing my current condition?
2.
What tests can I undergo to determine the exact cause? Should I get another MRI for confirmation?
3.
What could be the reason for the aspirated fluid not being clear? Is it simply inflammation, or could it be degenerative arthritis or synovitis?
4.
What could be causing the cracking sound in my knee?
Thank you for your response.

wing, 30~39 year old female. Ask Date: 2018/05/30

Dr. Cai Shanglin reply Orthopedics

The presence of effusion is generally a result of inflammation in the joint tissues.
The redness is likely due to the severity of the inflammation.
It is difficult to determine whether it is degenerative arthritis or periostitis.
If both MRI scans show no issues with the ligaments, I believe the reconstruction part should be fine.
If there are any doubts, I still recommend having the original surgeon examine you for a more accurate assessment.

Reply Date: 2018/05/30

More Info

Post-ACL surgery complications, such as knee swelling and pain, can be concerning for patients, especially when they persist long after the initial recovery period. Your situation, having undergone ACL reconstruction and meniscus repair, is not uncommon, and understanding the underlying causes of your symptoms is crucial for effective management.

1. Causes of Symptoms: The persistent swelling and pain you are experiencing can be attributed to several factors. After ACL reconstruction, the knee joint can remain inflamed for an extended period due to the surgical trauma, leading to synovitis (inflammation of the synovial membrane), which can cause excess fluid accumulation (effusion). The presence of red-tinged fluid suggests that there may be some bleeding within the joint, which could be due to irritation of the synovial lining or minor trauma to the surrounding tissues. This is often seen in cases of inflammation or irritation, and while it can be alarming, it does not always indicate a severe problem.

2. Further Investigations: To accurately determine the cause of your ongoing symptoms, further imaging studies may be warranted. An MRI can provide detailed images of the soft tissues, including the ligaments, cartilage, and synovial membrane, helping to identify any potential issues such as tears, inflammation, or other abnormalities. Additionally, a joint aspiration (the procedure you underwent to remove excess fluid) can be analyzed for cell counts, crystals, and other markers that can indicate inflammation, infection, or degenerative changes.

3. Nature of the Fluid: The non-clear appearance of the fluid you described could indicate inflammation or the presence of blood. Inflammatory joint conditions, such as post-surgical synovitis, can lead to the production of cloudy or bloody effusions. While degenerative joint disease (osteoarthritis) can also cause similar symptoms, it typically presents with chronic pain and stiffness rather than acute swelling post-surgery. Bone marrow edema or inflammation of the periosteum (the outer fibrous layer covering the bone) could also contribute to your symptoms.

4. Popping Sounds: The "clicking" or "popping" sounds you hear when moving your knee can be attributed to several factors, including the movement of tendons over bony prominences, the presence of scar tissue, or even the normal mechanics of the knee joint. In some cases, these sounds can be benign, especially if they are not accompanied by pain. However, if they are associated with discomfort or instability, further evaluation may be necessary to rule out any underlying mechanical issues.

In summary, your symptoms are likely a combination of post-surgical inflammation, possible irritation of the joint lining, and the normal healing process following ACL reconstruction. It is essential to continue working closely with your orthopedic surgeon and physical therapist to monitor your progress and adjust your rehabilitation program as needed. If your symptoms persist or worsen, further imaging or diagnostic procedures may be necessary to ensure that there are no complications that require intervention. Regular follow-ups and open communication with your healthcare team will be key to achieving a successful recovery.

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