Knee Effusion: RA Impact and Treatment Insights

Knee posterior flexion with effusion?

Hello Dr.
Lin: I have been diagnosed with rheumatoid arthritis (RA) based on some blood test results, but I have no clinical symptoms.
I was originally taking methotrexate (MTX) and steroids (for six months), but in February of this year, I experienced knee pain (with slight swelling behind the knee that is not easily noticeable to others, and I didn't pay much attention to it since I was focused on RA).
To date, I still have no clinical symptoms; the pain has somewhat alleviated, but I still feel discomfort when squatting and standing up.
I have also had an X-ray of my knee during this period, which showed no abnormalities.
During my follow-up appointment in September, the doctor indicated that since there are no clinical symptoms, my medication dosage needs to be adjusted.
Currently, I take my medications once a day in the morning, which includes 7.5 mg of Bone-Sensitive (a brand name for MTX), one quinine tablet, and one steroid tablet or a quarter of a tablet daily.
The doctor mentioned that in the future, he would discontinue Bone-Sensitive and steroids, replacing them with quinine.
Recently, as the weather has turned colder, I have been experiencing soreness behind my knee joint (in the flexed area).
On December 13, I visited an orthopedic doctor who arranged for an ultrasound examination today (December 14), which revealed some fluid accumulation behind my knee (about one centimeter).
Since I had a habit of hiking and climbing stairs (for two years) before the onset of my symptoms, the doctor suggested it might be an exercise-related injury, but he did not rule out the possibility of RA-related fluid accumulation in the back of the knee.
However, he repeatedly emphasized that RA typically starts in the small joints.
The doctor advised me to perform leg elevation exercises for six weeks, stating that the fluid might be absorbed by the body (surgery to remove the fluid sac would only be necessary if it becomes severe).
I would like to ask Dr.
Lin if it is possible for RA-related fluid to accumulate behind the knee.
I have read a lot of information about RA, including the RA Friends website, and have asked the moderator, but I have not seen any mention of fluid accumulation behind the knee; it seems to always swell or accumulate in the front of the knee.
Could you please clarify this for me?

MIMI, 30~39 year old female. Ask Date: 2005/12/14

Dr. Lin Xiaoyi reply Orthopedics

Hello,
This symptom is likely a Baker's cyst, which is mostly caused by issues within the knee joint (such as knee joint inflammation or injuries to the cartilage or ligaments within the knee) leading to fluid accumulation.
This fluid extends out from the weaker area of the knee joint capsule at the back of the knee, forming a cyst between the gastrocnemius and semimembranosus muscles.
Your condition seems more related to arthritis; if the diagnosis is confirmed as rheumatoid arthritis (RA), it is very likely that RA is affecting the knee joint, causing intra-articular fluid accumulation that leads to the formation of a Baker's cyst.
In this case, if the underlying knee joint issues are properly addressed, the cyst will likely gradually resolve.

If you are experiencing tightness in the knee joint, difficulty straightening or bending it, and symptoms such as redness, swelling, heat, and pain, it is very likely that you have knee joint inflammation.
Treatment methods are similar to those for RA and may include aspiration of the intra-articular fluid and corticosteroid injections, depending on the situation.

For rehabilitation, applying ice can help reduce inflammation, and using a knee brace while walking can temporarily reduce the burden on the knee joint.
Maintaining gentle exercise is also advisable.
Please discuss these recommendations with your rheumatologist.
Wishing you good health.
Sincerely,
Lin Hsiao-Yi
Department of Allergy, Immunology, and Rheumatology, Taipei Veterans General Hospital

Reply Date: 2005/12/14

More Info

Knee effusion, commonly referred to as "water on the knee," can be a significant concern for individuals diagnosed with rheumatoid arthritis (RA). Your situation, where you have been diagnosed with RA but are not experiencing typical clinical symptoms, is not uncommon. The presence of knee effusion, particularly in the context of RA, raises several important considerations regarding its causes, implications, and treatment options.

Firstly, it is essential to understand that RA is an autoimmune condition that primarily affects the joints, leading to inflammation, pain, and, in some cases, joint damage. While it is true that RA often manifests in smaller joints initially, it can also affect larger joints, including the knees. The accumulation of synovial fluid in the knee joint can occur due to inflammation of the synovial membrane, which is the lining of the joint. This inflammation can be triggered by various factors, including physical activity, joint overuse, or even the underlying autoimmune process of RA itself.

In your case, the ultrasound revealing approximately one centimeter of fluid accumulation behind the knee suggests a condition known as "popliteal cyst" or Baker's cyst, which can occur when excess synovial fluid escapes from the knee joint into the surrounding tissues. This can happen in individuals with RA, especially if there is underlying inflammation or joint damage. While it is less common for effusion to present behind the knee, it is not impossible, particularly in the context of RA.

Regarding your treatment plan, it is good to hear that your physician is monitoring your medication regimen closely. Methotrexate (MTX) and corticosteroids are commonly used to manage RA symptoms and inflammation. The adjustment of your medication, with a focus on reducing corticosteroid use and potentially replacing it with quinine, is a strategy aimed at minimizing side effects while maintaining disease control. It is crucial to follow your physician's recommendations and report any changes in your symptoms or new concerns.

As for the knee effusion, your doctor’s recommendation to perform leg raises and other exercises is beneficial. These exercises can help strengthen the muscles around the knee, improve stability, and potentially assist in the reabsorption of the excess fluid. However, if the effusion persists or worsens, further interventions, such as aspiration (removal of fluid) or corticosteroid injections, may be considered to alleviate symptoms and reduce inflammation.

In terms of your concern about RA causing fluid accumulation behind the knee, while it is less frequently documented, it is not outside the realm of possibility. The inflammatory processes associated with RA can lead to fluid accumulation in various areas of the joint, including atypical locations. It is essential to maintain open communication with your healthcare provider, who can provide personalized insights based on your specific condition and response to treatment.

In summary, knee effusion in the context of RA can occur and may present in various locations around the knee joint. Your treatment plan should be tailored to your individual needs, and it is crucial to monitor your symptoms closely. Engaging in recommended exercises and maintaining regular follow-ups with your healthcare provider will be key in managing your condition effectively. If you have any further questions or concerns, do not hesitate to reach out to your healthcare team for guidance.

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