Pain Behind the Knee

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

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. The pain may be fairly localised to the back of the knee or may extend downwards resulting in calf pain.

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

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

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.

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

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 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.

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

Hamstring tendonitis is an overuse injury where there is irritation and inflammation of the hamstring tendons at the back of the knee. It often affects athletes and runners.

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

Common symptoms of hamstring injuries include sharp pain behind the knee or in the thigh at the time of injury 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. 

8. Deep Vein Thrombosis (DVT)

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.

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.

7. 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.

Pain behind the knee when you first get up can also be from hamstring tendonitis. The pain usually eases off when you get moving but returns as soon as you do anything strenuous.