Top 5 Reasons to Drain Swelling Behind the Knee

OK, you’ve noticed you have swelling behind the back of your knee. Do you have any idea what this is called? Hopefully you have used Google to find the answer, and we’re pleased you have stumbled upon our page where we’ll talk you through it.

Check out this video that goes through the procedure of how we drain swelling behind the knee:

Swelling behind the Knee

This is a common problem, and the condition is known as a Baker’s cyst, or a popliteal bursitis. The cyst is not a traditional cyst. It is not a hard white swelling, like a kidney cyst. It is a soft accumulation of fluid in a natural pocket behind the back of the knee. This is why another term is also often used… popliteal bursitis. Popliteus = the muscle at the back of the knee, bursitis = swelling or inflammation of a sac of fluid. The literal translation means, swelling at the back of the knee.

Why do they form?

Common reasons include:

1. Osteoarthritis: if you have arthritis in your knee, the knee can swell up, and the swelling forms in the back of the knee.


2. Rheumatoid Arthritis: this can also cause the joint to become irritated and inflame, forming swelling behind the knee.


3. Idiopathic: this means there is no reason why it has happened, it just happened.


4. Trauma: you had some structural trauma to the knee causing swelling and/or bleeding, forming behind the knee.

Top 5 Reasons to Drain a Baker’s Cyst

1. Pain

Yes, it hurts. Taking the fluid out is also helping to reduce inflammation and swelling. This reduces hydrostatic pressure on the tendons, ligaments, and nerves at the back of the knee, meaning you get less pain.

2. Improve Range of Movement

When your knee is swollen, it often gets stiff. You will notice that bending the knee is painful and stiff, and you will lack a good range in the knee joint. Stiffness ends up causing more stiffness, so the less mobile your knee is, the more likely the knee will continue to stiffen up due to immobility.

3. Aesthetic

Some people just don’t like to have a lump of swelling at the back of their knee. To be fair, it’s not a hugely visible part of the body in most circumstances.

4. Mindset

People don’t like “cysts” being in them, and just want them removed. People don’t like swellings that should not be there. Even though a Baker’s cyst is completely benign, just the thought of having it there is enough to make most people want to get it drained.

5. Safe procedure

The process of draining fluid behind the back of the knee is reasonably straightforward and fairly safe. Yes, there are some very important structures behind the knee like the popliteal artery, the sciatic nerve, and the popliteal vein. We always miss them when we aspirate, as we usually use an ultrasound scanner to home in on the cyst and swelling. There is a risk of discomfort during the procedure, and most people feel discomfort, although once the needle is in, it’s not too bad and almost everyone tolerates it well.

The Solution

Drain it. We aspirate them. We get a syringe or two, the right sized needle, and following an ultrasound scan to identify the cyst, we drain it. It takes about 5-15 minutes depending on how large the cyst is. It costs just £120 to get the procedure done (price correct in 2024). In most cases, the cyst does not return once aspirated. However, sometimes it does. In these cases, we might suggest aspiration followed by a steroid injection if aspiration needs to be repeated.

If you are a patient and struggling with swelling behind your knee, and you just need it drained, we offer a great solution. Just call us or email us to book in with one of our team. Please note, not all of our therapists do this procedure, as it is highly specialised. So, please call us to discuss your case further and we can let you know who in our team is best to see. Call us on 0208 685 6930 or click the link at the top to book online.