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

The most common cause of pain behind the knee is a Bakers Cyst.

A Bakers Cyst develops when excess fluid in the knee joint seeps out into the popliteal bursa causing it to swell.

The main symptoms of a Bakers Cyst are tightness and pain behind the knee that gets worse when walking, kneeling, or bending the knee.

Treatment for a popliteal cyst focuses initially on reducing the swelling and pain behind the knee, and in severe cases the fluid may need to be drained by your doctor.

You can find out loads more about the causes, symptoms and treatment options in the Bakers Cyst Knee section.

2. Ligament Sprain

A knee sprain can cause pain behind the knee

Another common cause of pain behind the knee is a ligament sprain where one of the knee ligaments gets overstretched and tears.

Knee ligament tears are usually caused by a large force through the knee or sudden twisting movements e.g. quick pivoting when running in cleats/studs.

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. 

You can find out loads more about the causes, symptoms, treatment and recovery in the Knee Ligament Injuries section.

3. Posterior Cartilage Tear

A meniscus tear is a common cause of back of knee pain. Image source Orthoinfo AAOS http://bit.ly/2zWK60P

Another common cause of pain behind the knee is a tear in the cartilage at the back of the knee.

Cartilage damage may develop suddenly with an injury or gradually from wear and tear.

Cartilage injuries are usually accompanied by swelling, instability and difficulty straightening the leg and in some cases the knee may lock up.

Pain behind the knee from a cartilage tear typically gets worse when walking, running, climbing stairs and squatting. 

You can find out loads more about the causes, treatment and recovery process in the Knee Cartilage Injury section.

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.

Calf strains typically happened during activity, such as quickly changing speed or direction when running. If the calf muscles get over stretched and tear it can lead to swelling and pain behind the knee. 

The symptoms of calf tears typically get worse when walking or running, especially on tip toes.

You can find out loads more about the common causes, symptoms and best treatment options in the Calf Tear section.

5. Knee Arthritis

Arthritis is a common cause of posterior knee pain. Image source OrthoInfo AAOS http://bit.ly/2zVbjRN

A common cause of pain behind the knee in the over 50's is arthritis. With knee arthritis, there is gradual wear and tear of the knee bones and cartilage.

Knee arthritis may affect one or both sides of the joint and can result in bone rubbing on bone. 

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.

You can find out loads more about arthritis including the common causes, stages, treatment and surgical options in the dedicated Knee Arthritis section.

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. This damages the structures at the back of the knee, resulting in pain behind the knee.

Knee hyperextension is a common sporting injury that causes a sharp or aching pain behind the knee, swelling and instability. Symptoms usually get worse when standing, walking or going down stairs.

You can find out all about the common causes, symptoms and treatment options in the Hyperextended Knee section.



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. 

1. 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.

2. What Causes Tightness Behind The Knee? 

Pain and tightness behind the knee is a common problem

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.

3. 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.

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.

4. 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.

5. 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.

6. 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.

7. What Causes Pain Behind The Knee After Sitting? 

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

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. For more help, visit the knee symptoms diagnosis guide.

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

Page Last Updated: 05/24/22
Next Review Due: 05/24/24


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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