What it is
It may get bigger and smaller over time and sometimes goes away on its own. Treating the underlying knee problem often helps.
Occasionally a cyst bursts and fluid runs down into the calf, causing pain and swelling that can look like a blood clot, so this needs checking.
Common signs
- A swelling behind the knee
- Tightness or stiffness, especially when bending the knee
- Knee pain
How it is usually diagnosed
- Examination of the knee
- Ultrasound to confirm the cyst and rule out a blood clot
- MRI if a cartilage problem is suspected
Records worth keeping
Keeping these together makes each appointment easier, especially when you see a new doctor:
- Ultrasound and MRI reports
- Notes from orthopaedic or physiotherapy visits
Questions to ask your doctor
- What is causing the fluid to build up?
- Does the cyst need draining?
- How can I tell a burst cyst from a blood clot?
When to get help right away
Call 112 or go to the nearest emergency department if you have:
- A swollen, painful, red or warm calf, especially with breathlessness or chest pain: seek care urgently, it may be a blood clot
This page is general information. It is not a diagnosis and does not replace a doctor who knows your history. Medfold keeps your records organised; it does not interpret them.