Synovial Effusion: Causes, Treatments, Recovery Time

Have you been diagnosed with synovial effusion in a joint (knee, ankle, hip, elbow, shoulder, etc.)?

It’s very common, and in the vast majority of cases benign , although sometimes quite annoying.

I take a look at the questions patients most often ask their physiotherapists when they have this problem.

♻️ Last update: March 24, 2025.
👩‍⚖️ Declaration of financial interests: none directly related to the subject. My complete declaration of interest is in the legal notice section.
Written by Nelly Darbois, physiotherapist and scientific editor

What is a synovial effusion?

A synovial effusion is when a certain type of fluid accumulates in a joint.

This fluid is normally present in the joints to lubricate them, but sometimes it can multiply: being present in greater quantities.

What causes the joint to swell: it’s visually bigger, wider than usual, or on the side where it’s not swollen.

This can occur in most joints. But the most frequent locations are :

• the knee,
• elbow,
• ankle and foot,
• and hip.

A clinical examination is generally sufficient to diagnose an effusion. Complementary tests such as an X-ray, ultrasound or puncture of the fluid are used only when there is doubt about the diagnosis, to rule out another problem.

Effusion usually occurs as a result of :

• an injury,
• infection,
• arthritis,
• or inflammatory diseases such as gout.

This can also happen to children.

How long does a synovial effusion last?

Many parameters will influence the time it takes for the effusion to leave.

Here are two examples of very different healing times.

🏃‍♀️ Example 1 : Mirelle is 24 and a trail runner.

At the end of a long downhill run, she twisted her knee.

His knee swelled that evening and the next day, but there were no other symptoms. It’s a simple synovial effusion in the knee.

She’s able to walk and even run, even if it’s a little uncomfortable.

After 5 days, the swelling (and therefore the effusion) disappears, without her having done anything special.

🦴 Example 2: John is 82 and has a lot of osteoarthritis.

A few years ago, he underwent surgery on his right knee for gonarthrosis.

For several months now, her left knee has been swollen: it’s a synovial effusion, most likely related to osteoarthritis.

As long as the associated pain is bearable and doesn’t interfere with his activities, his surgeon tells him to let things take their course.

The effusion is likely to remain “for life”, unless a knee prosthesis is fitted, which is justified only in cases of pain and functional discomfort.

What does it mean? A synovial effusion lasts from a few days at best, to several months or even a lifetime.

Is it possible to walk despite the effusion?

You can still walk with a synovial effusion in your foot, knee or hip.

🚶‍♂️ On the contrary, moderate walking can help drain excess fluid and prevent stiffening of the joint.

⚠️ If pain or swelling increases after walking, it’s not necessarily the walking itself that’s the problem, but perhaps a poor dose of effort.

In this case, it may be useful to :

• reduce the intensity or duration of walking ;
• alternate with longer rest periods;
• use a technical aid (crutch, cane, etc.) to relieve pressure. The less weight you put on the joint, the less strain it will be subjected to.

How is synovial effusion treated?

Depending on its origin, an effusion may disappear on its own, without any specific treatment.

In this case, the main line of treatment will be to relieve pain, if present, while waiting for the spontaneous disappearance of the sprain.

In this case, you can use :

• a splint to rest the joint (often dispensable);
• cold application;
• taking painkillers (paracetamol or even NSAIDs).

If the fluid doesn’t go away on its own after several weeks, and the discomfort or pain is very severe, fluid puncture is sometimes considered. This is not a miracle cure, as the fluid may return.

Sometimes, corticosteroid injections into the joint are also proposed.

🚑 If infection is suspected (rare), intravenous antibiotic therapy should be initiated after joint fluid analysis.

🔬 The most common bacteria responsible for septic arthritis are :

• Staphylococci (40%)
• Streptococci (28%)
• Gram-negative bacilli (19%)
• Mycobacteria (8%)
• Gram-negative cocci (3%)
• Gram-positive bacilli (1%)
• Anaerobes (1%)

Does exercise help?

There are arguments in favor of doing exercises that challenge the swollen joint, and arguments against.

Arguments in favor of exercising in case of effusion :

• helps drain synovial fluid by stimulating blood and lymph circulation;
• prevents stiffening: prolonged immobilization can aggravate stiffness and slow recovery;
• strengthens the muscles around the joint to stabilize it and reduce the risk of recurrence;
• improves joint function by maintaining range of motion and preventing loss of mobility;
• reduces long-term inflammation: moderate activity can help regulate synovial fluid balance and reduce chronic pain;
• accelerates recovery if exercises are well balanced and adapted to the condition of the joint.

Now, there are also arguments against exercises:

• Risk of aggravating inflammation if the joint is already very swollen and painful;
• can increase pain if exercises are too intense or repeated;
• can slow healing if stress exceeds the body’s capacity for regeneration.

There are no well-conducted clinical studies that allow us to say that people with effusions recover better with more or less exercise.

There’s a fine balance to be struck, and your physiotherapist can help you find it.

Note that there’s no single exercise that’s better than another: it’s the movement of the joint that counts, whatever the movement.

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That’s all I wanted to say on the subject! Any questions or comments? See you in comments!