Pain Behind the Knee

Written By: Chloe Wilson, BSc(Hons) Physiotherapy
Reviewed by: KPE Medical Review Board

Find out about the most common causes of pain behind the knee and how to treat them

Pain behind the knee is a common problem. Not only can it affect your ability to walk and carry out your usual activities, back of knee pain can also really affect your sleep.

Also known as posterior knee pain, pain behind the knee may develop gradually over time, or suddenly with an injury. 

There may be a general ache, leg movements may be restricted by swelling or there may be a sharp pain at the back of the knee. 

What Causes Pain Behind The Knee?

Here we look at the most common causes of pain behind the knee, how and why they develop, will help you work out what is causing your posterior knee pain and how best to treat it.

1. Bakers Cyst

A Bakers cyst is the most common cause of back of knee pain. Find out about the causes, symptoms, diagnosis and treatment

A Bakers Cyst is the most common cause of pain behind the knee. Also known as a popliteal cyst, it develops when excess swelling in the knee seeps out of the back of the joint and pools in the popliteal bursa. The bursa becomes inflamed and swollen and people often say it feels like they have a squashy orange behind their knee.

Anything which causes swelling in the knee can lead to a Bakers Cyst, but the most common culprit is knee arthritis. In fact, around half of all knee arthritis sufferers will develop a Bakers Cyst at some point. Other common causes include gout, knee cartilage tears or a strong blow to the back of the knee.

A Bakers cyst usually causes tightness and pain behind the knee that gets worse when walking, kneeling, or bending and straightening the knee. The swelling at the back of the knee may fluctuate with a Bakers Cyst. Treatment focuses initially on reducing the pain and swelling, and in severe cases, the fluid may need to be drained by your doctor, known as aspiration.

Strengthening and stretching exercises for a Bakers Cyst help to reduce the chance of recurrence, a common problem without correct treatment. 

Find Out More: Bakers Cyst - Causes, Symptoms & Treatment

2. Ligament Sprain

A knee sprain can cause pain behind the knee

Another common cause of pain behind the knee is a ligament sprain. This is when one or more of the four knee ligaments gets overstretched and tears.

Knee ligament tears are usually caused by sudden twisting movements or a large force through the knee. Quick pivoting when running in cleats/studs is a common cause as the foot is held rigid while the rest of the body turns, twisting the knee. 

Common symptoms of a ligament sprain include knee instability, swelling and bruising and the associated pain behind the knee can lead to knee stiffness and difficulty walking. 

The most common knee ligaments to injure are the

Treatment for a sprained knees initially focuses on reducing pain and inflammation, and once that is under control, the focus shifts to strengthening and stability exercises to regain full knee function.

Find Out More: Knee Ligament Tears - Causes, Symptoms & Treatment

3. Posterior Cartilage Tear

A meniscus tear is a common cause of back of knee pain. Image source Orthoinfo AAOS

A tear in the cartilage at the back of the knee is another common cause of pain behind the knee.

The knee is lined with a thick extra layer of cartilage, known as the meniscus, to protect it from repetitive impact. Think of it like an inbuilt shock absorber. 

Cartilage damage may develop:

  • Suddenly: usually from twisting the knee awkwardly or from a large force through the knee
  • Gradually: wear and tear over time causes thinning and fraying of the cartilage

Any activities that load the back portion on the knee joint can cause pain behind the knee with a cartilage tear e.g. walking, running, climbing stairs and squatting. There is often swelling, instability and difficulty straightening the leg after a meniscus tear, and if a fragment of torn cartilage gets stuck in the joint, the knee may lock up.

Meniscus tear treatment may include rest, ice, compression, elevation, and an exercise rehab program to reduce the pain behind the knee and restore full movement. If the knee keeps giving way, then you may need to wear a knee brace and in some cases, surgery may be required.

Find Out More: Knee Cartilage Tears - Causes, Symptoms & Treatment

4. Calf Tear

A Calf Tear is a common cause of pain behind the knee. Learn about the causes, symptoms, diagnosis and treatment of calf muscle injuries

Pain behind the knee that is lower down in the calf region may be due to damage and tearing of one of the calf muscles, known as a calf strain.

Calf strains typically happened during activity, such as quickly changing speed or direction when running. The calf muscles get over stretched and tearing in the muscles leads to swelling and pain behind the knee. 

This usually results in back of knee pain and swelling and the symptoms of a calf tear typically get worse when walking or running, especially on tip toes.

Find Out More: Calf Tears - Causes, Symptoms & Treatment

5. Knee Arthritis

Arthritis is a common cause of posterior knee pain. Image source OrthoInfo AAOS

Arthritis is another possible cause of pain behind the knee. With knee arthritis, there is gradual wear and tear of the knee bones and cartilage. This erosion leads to the formation of bone spurs, and damages the smooth joint surfaces, as well as reducing the space between the knee bones

As a result, the bones and cartilage rub against each other as the knee moves which is not only painful, but can actual restrict movement.

Common symptoms of knee arthritis include knee stiffness (particularly in the morning), clicking or grinding noises and restricted knee mobility. Symptoms often fluctuate and may get worse during cold, wet weather.

Arthritis is most commonly seen in people over the age of 60 and has been linked with obesity and previous knee injuries or surgery. There is thought to be a genetic link and arthritis is more common in women compared to men.

Treatment for knee arthritis focuses on exercises to strengthen the muscles around the knee and to keep the joint mobile and flexible. Alternative treatments such as acupuncture, supplements and homeopathy are becoming increasingly popular as well. 

Many people with knee arthritis are able to manage their symptoms at home, but with more severe cases, surgery may be recommended, typically a knee replacement.

Find Out More: Knee Arthritis - Causes, Symptoms & Treatment

6. Hyperextended Knee

A hyperextended knee is where the knee is bent back too far causing damage and back of knee pain

A hyperextended knee is an injury where the knee bends back too far, damaging the structures at the back of the knee, resulting in pain behind the knee.

Knee hyperextension is a common sporting injury e.g. from an awkward tackle or skiing accident that forces the knee backwards. There tends to be a sharp or aching pain behind the knee, swelling, bruising and instability. Symptoms typically get worse when standing, walking or going down stairs.

PRICE treatment (protect, rest, ice, elevate, compress) tends to be the first port of call for treatment, followed by strengthening and stability exercises. If there is significant instability in the knee, then a knee brace may be helpful, but if one of more of the knee ligaments have ruptured, then surgery may be necessary.

Some people are naturally hyper-flexible and may find their knee has always bent back too far. This is known as genu recurvatum syndrome. It has been linked to various medical conditions, ligament laxity and muscle weakness.

It is really important to get proper advice and treatment for knee hyperextension, not only to reduce pain behind the knee, but also to reduce the risk of further knee injuries.

Find Out More: Hyperextended Knee: Causes, Symptoms & Treatment

7. Deep Vein Thrombosis (DVT)

A deep vein thrombosis (DVT) is a potentially life-threatening cause of pain behind the knee and in the calf

Another possible cause of pain behind the knee is  Deep Vein Thrombosis. A DVT is a blood clot found in one of the deep leg veins. If it breaks off it can lead to a heart attack or stroke. 

The symptoms to watch out for that indicate a possible DVT include pain behind the knee or in the calf region associated with swelling, redness and warmth in the area. Symptoms are usually only felt in one leg, not both. 

People are at higher risk of developing a DVT after prolonged inactivity e.g. long-haul plane journey or after surgery. Pregnancy, obesity, genetics and certain medical conditions also increase the risk.

Self-Test: Pull your toes up towards you (your foot doing the work, not your hands) - an increase in the pain behind the knee/calf indicates possible DVT

Safety Warning: A DVT is a potentially life-threatening condition. If you are showing symptoms of a DVT seek immediate medical attention, even if the self-test is negative.

8. Hamstring Injuries

Hamstring injuries are a common cause of pain behind the knee and thigh

Pain behind the knee or in the back of the thigh may be caused by a tear in one of the hamstring muscles.

Hamstring tears develop when one of the muscles is overstretched, beyond their elastic limit, causing some or all of the muscle fibres to tear. This typically happens during sporting activities with sudden, fast movements e.g. sprinting, lunging and jumping. 

Common symptoms of a hamstring tear include sharp pain behind the knee or in the thigh at the time of injury, depending on where the tear is, which is usually followed by a dull aching sensation. The pain tends to get worse when bending the knee or with sudden acceleration or deceleration. 

It is important to avoid any aggravating activities after a hamstring tear to allow it time to heal - if you put too much strain through the injured muscle, it is likely to re-tear.

Gentle hamstring strengthening exercises can be started after a couple of days, as long as they don't aggravate symptoms. Once you can confidently do these without any pain, then it is really important to do hamstring stretches to regain flexibility in the muscle and ensure that the fibres heal in the right position.

Frequently Asked Questions

Here, you can find answers to the questions we are most commonly asked regarding symptoms associated with back of knee pain. 

What Causes Pain Behind The Kneecap? 
Pain behind the kneecap is usually caused by a problem with the cartilage that lines the back of the kneecap. It may be Runners Knee, where a problem with how the kneecap glides causes friction and pain behind the kneecap.

In teenagers, pain behind the kneecap is often caused by Chondromalacia Patella, a condition where there is thinning of the cartilage on the back of the kneecap.

Pain and tightness behind the knee is a common problem

What Causes Tightness Behind The Knee? 
Tightness behind the knee is often caused by tightness in the hamstring or calf muscles. The hamstring muscles run down the back of the thigh attaching behind the knee, and one of the calf muscles, gastrocnemius, starting from the back of the knee, travels down to the heel.

Tightness in these muscles is a common problem, particularly in men, and makes the back of the knee feel very tight. Simple knee stretches are the best way to treat the tightness and relieve back of knee pain.

What Causes Swelling Behind The Knee? 
Swelling behind the knee is most commonly caused by a Baker's Cyst. Excess fluid in the knee joint, usually from an injury or knee arthritis, leaks out of the back of the joint.

This fluid fills the semimembranosus bursa and causing swelling behind the knee. It often feels like there is a squashy orange behind the knee which can be really painful.

Other possibilities of back of knee swelling include a calf tear, popliteal aneurysm and a synovial sarcoma. Find out more in the swelling behind the knee section.

What Causes Sharp Pain Behind The Knee? 
If you are a runner, then sharp back of knee pain often indicates a problem with the hamstring tendons, such as tendonitis. If you do a lot of cycling, then a sharp pain behind your knee is usually caused by a problem in one of the calf muscles, gastrocnemius.

If you have recently twisted your knee or had a fall, then a meniscus tear is probably causing the sharp pain.

What Causes Pain Behind The Knee When Bending? 
The most common cause of pain behind the knee when bending is a Bakers Cyst. This is when there is inflammation of the semimembranosus bursa, a small sac filled with fluid that sits at the back of the knee.

If the bursa gets inflamed, then any time you bend your knee, the bursa gets squashed, causing posterior knee pain.

What Causes Pain Behind The Knee When Straightening The Leg? 
The most common cause of knee pain when you straighten the leg is a meniscus tear, particularly if you've been sitting down or squatting for a while.

As the knee straightens out from a bent position, the torn, inflamed portion of cartilage gets squashed in the joint, causing back of knee pain.

Pain behind the knee after sitting for a while is a common feature of arthritis

What Causes Pain Behind The Knee After Sitting? 
Pain behind the knee after sitting for prolonged periods is often caused by arthritis. When we sit still, the fluid that lubricates the knee joint dries out slightly so when we then stand up, there is less cushioning.

The wear and tear associated with arthritis mean you can end up with the knee bones rubbing together, causing knee pain. Once you are up and moving about, the joint produces more synovial fluid so, after a few minutes of moving around, the back of knee pain eases off.

Treating Back Of Knee Pain

So what's the best back of knee pain treatment? The best treatment for pain behind the knee will depend on what's causing the pain. Generally, the first step is to reduce any swelling, then work on knee exercises to improve the strength and stability of the knee to reduce the force that goes through the knee joint.

Just because there is back of knee pain, it doesn’t necessarily mean the problem is there. Pain can refer to different places so a problem around the front of the knee can produce a feeling of posterior knee pain.

Remember, the best way to accurately diagnose the cause of your pain behind the knee is to see your doctor. 

Page Last Updated: 10/06/21
Next Review Due: 10/06/23

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Medical & Scientific References

Posterior Knee Pain by S. English & D. Perret. Journal of Current Reviews in Musculoskeletal Medicine, Oct 2010
Pain Behind Knee? Injury vs. Disease-Related Causes from University Health News, March 2018
Bakers Cyst - NHS UK June 2018
Meniscus Tears - OrthoInfo. American Academy of Orthopedic Surgeons