Pain behind the knee is also called posterior knee pain. ‘Posterior’ just means behind.
As well as pain, you may have swelling just at the back of the knee or that extends into the calf. The swelling may be large enough to stop you bending your leg properly.
Managing pain behind the knee
You can help yourself by keeping weight off your leg as far as possible, using an ice pack and taking painkillers. If you can’t put weight on your leg, you may need crutches.
Popliteal cysts often get better on their own and you may not need any further treatment. But it’s a good idea to see a doctor if you have pain behind the knee. It may be something more urgent (such as a blood clot in the leg). With posterior cruciate ligament injury, you can develop complications later if you are not treated. You should see a doctor if:
- you cannot put weight on the affected leg
- you have severe pain, even when not bearing weight
- your knee buckles, clicks, or locks
- your knee is deformed or misshapen
- your knee is hot, red or very swollen or you have a fever
- you have pain, swelling, numbness, tingling, or a bluish discoloration in your calf
- you’re still in pain after three days
Treatment of pain behind the knee
The treatment that you have for pain behind your knee will depend on what condition is causing the pain.
Diagnosis of pain behind the knee
Your doctor will examine your knee and take a history, asking about:
- the type of pain you have, when it started and whether it comes and goes
- how active you are
- any activity, accident or injury that could have caused it
If you have signs of a popliteal cyst, your doctor may suggest an ultrasound scan. If they suspect a posterior cruciate ligament injury, they may suggest an X-ray or a magnetic resonance imaging (MRI) scan.
Symptoms of pain behind the knee
Symptoms you may have with pain behind the knee will vary, depending on the cause. You may have swelling or pain with particular movements.
A popliteal cyst causes swelling at the back of the knee, which can be quite noticeable. A very large swelling may stop you from fully straightening your leg.
The swelling may come and go, getting bigger or shrinking over time. If the cyst bursts, you may have swelling and pain in your calf.
If you have a swollen, tender calf, it’s very important to see a doctor as the swelling can also be caused by a clot in your leg (deep vein thrombosis), which needs to be treated urgently.
If your cyst bursts, you may hear a pop and feel warmth spread down your calf. You may develop redness or bruising anywhere from the back of your knee down to your ankle and the top of your foot.
With a posterior cruciate ligament (PCL) injury, it’s more common to have other knee injuries as well. But if you have only injured your PCL, you may just feel vague discomfort or instability in your knee. You may feel pain behind your knee, but some people have pain at the front of the knee as well. You may also have pain when kneeling. A chronic or long-term PCL injury can cause pain when slowing down from running, walking downhill or going down stairs.
Osteoarthritis usually causes pain when you’re bearing weight, which is relieved by rest. Stiffness and loss of movement is often worst first thing in the morning or after sitting for a while and eases once you start moving around.
