Pain behind the knee (posterior pain)
Your health expert: Mr Gareth Stables, Specialist Knee Surgeon
Content editor review by Rachael Mayfield-Blake, November 2023
Next review due November 2026
Pain behind the knee is also called posterior knee pain. ‘Posterior’ means behind. As well as pain, you may have some swelling. This may be just at the back of your knee or it can spread into your calf. The swelling may be bad enough to stop you bending your leg properly.
Causes of pain behind the knee
There are several causes of back of the knee pain. Your knee joint may wear down as you get older – for example, you may have osteoarthritis or rheumatoid arthritis. Or you may get a knee injury (ligament injury or torn cartilage).
The most common injuries or health conditions that may cause pain behind your knee include the following.
Hamstring injury
If you strain or tear your hamstring muscle on the back of your thigh, it can lead to pain behind your knee and difficulty bending it. This may happen if you overstretch or do any sudden, forceful movements.
Popliteal cyst (Baker’s cyst)
A cyst is a collection of fluid or material inside a thin layer of tissue. A popliteal cyst (Baker’s cyst) is a cyst in the shallow pit at the back of your knee. It’s often linked to other conditions that affect the knee, such as osteoarthritis, rheumatoid arthritis, or cartilage injuries. If you injure your knee, it can cause a collection of fluid to develop within your knee. Sometimes you can feel this in the back of your knee.
Meniscus tear
The menisci are two crescent-shaped pads of thick, rubbery shock-absorbing cartilage in your knee joint. They can tear after an injury, such as twisting your knee, or due to wear and tear. A meniscus tear can cause pain in the back of your knee, especially when you bend or twist your knee.
Posterior cruciate ligament injury
Your posterior cruciate ligament (PCL) runs across your knee from your thigh to your shin bone. A PCL injury can happen if you overstretch or tear this ligament. It often results from a heavy blow to the front of your knee while it’s bent. This can happen if you hit your knee on the dashboard during a car accident. Or if you’re playing sport and have a direct blow to your knee from a collision with another player.
Osteoarthritis
Osteoarthritis of the knee is another common cause of knee pain. The smooth, shiny cartilage that lines your knee joint becomes worn and rough. This causes pain and damages your knee over time. It mostly affects people over 50. The older you are, the more likely you are to get it.
Other causes of knee pain include an infection (septic arthritis), or a benign or cancerous growth but these are rare.
Symptoms of pain behind the knee
Symptoms of pain behind the knee will vary, depending on the cause. You may have swelling or pain when you move your knee a certain way.
A hamstring injury can cause pain when you put weight on your leg. And you may find it difficult to walk normally because it may feel stiff and painful to bend your knee.
A Baker’s cyst causes swelling and sometimes pain at the back of your knee, which you’ll probably notice. If you have a very large swelling, it may stop you from fully straightening your leg. The swelling may come and go, and get worse or better over time. If your cyst bursts, you may hear a pop and feel warmth spread down your calf. It may start to look red too.
A meniscus tear can cause pain in the back of your knee, especially when you bend or twist your knee. You may feel a ‘pop’ if you tear your meniscus. You may have some swelling, usually several hours after you injure the injury to your meniscus. Your knee may feel like it’s catching or locking too.
Osteoarthritis usually causes pain when you put weight on your knee, and gets better when you rest. Your knee may be stiff and you might not be able to move it as well in the morning or after you’ve been sitting down. This usually eases once you start moving around. You may also have some swelling over your knee.
If you have a posterior cruciate ligament injury (PCL injury), you’ll probably have injured other parts of your knee too. But if you’ve only injured your PCL, you may just feel a bit of discomfort or potentially, nothing at all. With a more severe injury, you may feel pain behind your knee, especially when you kneel. It may be uncomfortable going down an incline too. For example, you may have pain behind your knee when walking, running downhill, or going down stairs.
If you have a swollen, tender calf, it’s very important to see a doctor. This is because such a swelling can also be caused by a clot in your leg (deep vein thrombosis), which you’ll need urgent treatment for.
Diagnosis of pain behind the knee
Your doctor will examine your knee and ask about your medical history and symptoms, including:
- the type of pain you have, when it started, and if it comes and goes
- how active you are
- any activity, accident, or injury that could have caused the pain
If they suspect you have a posterior cruciate ligament injury, they may refer you to have an X-ray or a magnetic resonance imaging (MRI) scan. If you have signs of a Baker’s cyst, your doctor may suggest you have an ultrasound scan.
Self-help for pain behind the knee
There’s a lot you can do to help yourself if you have a knee injury. It’s a good idea to follow the POLICE (PDF, 0.5MB) procedure.
Protect. Protect your injury from further damage. Rest immediately after the injury but not for long. Consider using some form of support or crutches.
Optimal Loading. Get active sooner rather than later. Start to put weight on your knee and build up your range of movement. Do this gradually – be guided by what feels right for you.
Ice. Place a cold compress such as a bag of ice or frozen peas wrapped in a towel onto your knee. Do this for around 20 minutes every couple of hours for the first two to three days.
Compression. Compress your knee using a bandage to help reduce swelling.
Elevation. Elevate your knee above the level of your heart to reduce swelling. Sit or lie on a chair and use a cushion to raise your leg.
Infographic: POLICE principles
Bupa's POLICE infographic (PDF, 0.5 MB), illustrates the ‘POLICE principles’ to reduce your pain and help you to recover. Click on the POLICE image below to download the PDF.
And there are certain things you should avoid in the first three days after your injury so you don’t damage your knee further. These can be remembered as HARM (PDF, 0.6 MB), which stands for the following.
H – Heat. Don’t have hot baths, showers, or saunas, and avoid heat packs and rubs.
A – Alcohol. Drinking alcohol can slow down your recovery and mask your symptoms – increasing the risk that you’ll injure yourself again.
R – Running. Don’t run or do any other form of moderate exercise.
M – Massage. Massaging the affected areas can cause more swelling and damage, so avoid this for the first day or two.
Infographic: HARM principle
Bupa's HARM infographic (PDF, 0.6 MB), illustrates the ‘HARM principle' of things you should avoid doing in the first three days after your injury. Click on the HARM image below to download the PDF.
Both POLICE and HARM are guidelines you can follow to treat any type of soft tissue injury to your knee, including pain behind the knee.
Baker’s cysts often get better on their own and you may not need any treatment. But it’s a good idea to see a doctor if you have pain behind the knee. It may be a sign of something more urgent (such as a DVT in your leg).
You should see a doctor if:
- you cannot put weight on your leg
- you have severe pain even when you don’t put any weight on it
- your knee buckles, clicks, or locks
- your knee looks deformed or misshapen
- your knee is hot, red or very swollen or you have a fever
- you have pain, swelling, numbness, tingling, or your calf looks blue
Treatment of pain behind the knee
Treatment for pain behind your knee will depend on what condition is causing the pain.
For information on how to treat pain behind the knee, please see the relevant page for each type of knee condition. For example, treatment for:
Looking for physiotherapy?
You can access a range of treatments on a pay as you go basis, including physiotherapy.
To book or to make an enquiry, call us on 0370 218 6528∧
There are various causes of pain at the back of the leg behind the knee. Your knee joint can wear down as you get older or you might injure your knee and tear the ligament or cartilage in it. A common condition that causes pain behind the knee is a popliteal cyst (Baker’s cyst).
For more information, see our section on causes of pain behind the knee.
If you injure your knee, you could try to relieve the pain by putting some ice on it – but wrap the ice in a tea towel first so you don’t hurt your skin. Put your leg up on a cushion too. If you can’t put weight on your leg, you may need crutches.
For more information, see our section on self-help for pain behind the knee.
A pulled tendon behind your knee can feel very painful. If you injure the biceps femoris tendon, for example, you may feel sharp pain at the back of your knee and thigh. The biceps femoris tendon attaches your hamstring muscle at the back of your thigh to your knee. You may feel a pop in your knee when you straighten and bend your leg. You might not be able to walk or walk normally.
Pain behind the knee isn’t usually something you should be worried about because with some form of treatment, most people recover well. But sometimes knee injuries can lead to complications so it’s important to see a health professional if you have problems. And if you have a swollen and tender calf, it’s very important to see a doctor. This sort of swelling can also be caused by a clot in your leg (deep vein thrombosis), which you’ll need urgent treatment for.
For more information, see our section on symptoms of pain behind the knee.
Anterior cruciate ligament (ACL) injury
An ACL injury can be a partial or a complete tear, an overstretch, or a detachment of the ligament.
Lateral collateral ligament (LCL) injury
An LCL injury is often associated with injuries to the ligaments and tendons in this area, as well as to other parts of the knee.
Medial collateral ligament (MCL) injury
The MCL is the most commonly injured knee ligament. It often gets injured during sports such as rugby.
Meniscal tear
Tears of the menisci are a common injury. When people talk about a ‘torn cartilage’ in their knee they usually mean a meniscus injury.
Patellar tendinopathy (jumper's knee)
Patellar tendinopathy is also called ‘jumper’s knee’ because the injury commonly occurs during sports that involve jumping, such as basketball.
Patellofemoral pain syndrome
Patellofemoral pain syndrome is sometimes called ‘runner’s knee’ because it’s particularly common in people who run or do other sports.
Other helpful websites
Discover other helpful health information websites.
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