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.

Posterior knee pain 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. 

Common Causes of Back Of Knee Pain

Here we look at the most common causes of pain behind the knee and then go on to look at each one in depth with loads of great advice on how to ease your back of knee pain.

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

Swelling develops in the popliteal bursa at the back of the knee. Bakers Cyst is the most common cause of pain behind the knee.

Causes: Excess fluid in the knee e.g. from an injury or arthritis

Symptoms: swelling behind knee, tightness and back of knee pain when bending the leg, walking and kneeling

Find Out More: Bakers Cyst Knee

2. Knee Sprain

A knee sprain can cause pain behind the knee

Overstretching of one or more knee ligaments, which can result in a full or partial thickness tear

Causes: Sudden twisting movements or a large force through the knee

Symptoms: Knee instability, back of knee pain, swelling, bruising, decreased knee movement

Find Out More: Knee Ligament Sprains

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 aka meniscus at the back of the knee

Causes: Sudden twisting, a force through the knee or gradual wear and tear

Symptoms: Swelling, locking and pain behind the knee with knee extension, walking, running, squatting & going up stairs 

Find Out More: Meniscus Tears

4. Calf Strain/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

Overstretching, partial or complete tear of one of the two calf muscles

Causes: Suddenly changing speed or direction when running, or repetitive running or jumping

Symptoms: Pain in back of knee or calf, bruising, swelling & difficulty walking. Worse when running or on tiptoes

Find Out More: Calf Strains

5. Knee Arthritis

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

Erosion of the knee bones and cartilage, bone spur formation, loss of joint space. Most common in the over 50's

Causes: Aging, obesity, previous knee injury or surgery, genes, gender

Symptoms: Knee stiffness, pain,  clicking, grinding, reduced leg movements. Worse with prolonged rest, activity, cold weather

Find Out More: Knee Arthritis

6. Hyperextended Knee 

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

An injury where the knee bends back too far damaging the structures at the back of the knee

Causes: Sporting injury where knee is pushed backwards e.g. awkward tackle or skiing accident

Symptoms: Sharp or aching pain behind the knee, swelling, bruising and instability. Worse standing, walking, going down stairs

Find Out More: Hyperextended Knee

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

A DVT is a blood clot in one of the deep leg veins. If it breaks off it can lead to a heart attack or stroke

Causes: Prolonged inactivity, certain medical conditions, pregnancy, obesity, genetics

Symptoms: Pain behind the knee or in the calf, swelling, redness, warmth, usually only on one leg

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

8. Hamstring Injuries

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

Overstretching the hamstring muscles on the back of the thigh beyond their elastic limit so they tear

Causes: Sudden, fast movements e.g. sprinting, lunging & jumping

Symptoms: Aching behind knee/thigh, sharp pain behind the knee. Worse when bending knee or with sudden acceleration or deceleration

Common Pain Behind The Knee 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.

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.

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.

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.

What Can Help 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. 

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Page Last Updated: 17/06/21
Next Review Due: 17/06/23

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 

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