In general, pain behind the knee is one of the more challenging musculoskeletal problems. There are many possible causes – muscle tear, tendon, nerve damage, and blood clots. But, like most other problems, the key to properly managing it is an early and accurate diagnosis. So, what causes pain behind the knee, and how do you find the cause?

What’s behind the knee?

The back of the knee has complicated anatomy.

As well as the knee joint sitting in the middle, the thigh and calf muscles pass through this area. Firstly, the large hamstring muscles start from the pelvis and pass across the knee to attach to the lower leg bones. In addition, the large calf muscles begin at the bottom part of the thigh and cross the knee to form the large Achilles tendon.

Finally, vital nerves and blood vessels cross the back of the knee to supply the lower leg and foot.

Common causes of pain behind the knee

Where do we start with making an accurate diagnosis?

Generally, most doctors use a methodological process to confirm or rule out causes. Firstly, we perform a thorough assessment to test the joints, ligaments, and tendons that pass across the back of the knee. Then, we consider imaging to confirm our thinking. X-rays often pick up major arthritis in the knee. MRI can detect soft tissue problems such as tendonitis or muscle tear. Occasionally, we perform other tests such as blood, ultrasound, or nerve studies, depending on the presentation.

Click on the back knee location chart to find possible causes. Follow the links to find out more information about each cause.

back knee pain location chart
Inside back of knee Top of the calf Outside back of the knee Central back of the knee

Top of the calf

Calf tear

Deep venous thrombosis

Outside back of the knee

Lateral Meniscal tear 

Lateral compartment osteoarthritis

Knee joint capsulitis 

Biceps femoris tendonitis (low hamstring)

Popliteus tendonitis 

Central back of the knee

Generally, the more common causes of pain behind the knee include the following:

Arthritis of the knee causing pain behind knee

Osteoarthritis is a common cause of pain behind the knee. Typically, arthritis causes bone spurs leading to inflammation at the back of the knee. Often, you feel tight and restricted in the movement of the knee joint.

Generally, the best form of treatment for knee arthritis is exercise and load management. Also, wearing a knee sleeve can help. Occasionally, we use injection therapy to help with arthritis, such as cortisone or platelet-rich plasma.

Meniscal tears  

 

Meniscal or cartilage tears of the knee can cause pain behind the knee – usually more on the inside or outside. Most of these tears are degenerative. Sometimes, however, the ‘root’ of the meniscus tears, where the meniscus attaches to the middle of the knee, tears. In these cases, the meniscus stops acting as a true shock absorber leading to increased stress on the knee joint.

Primarily, treatment of degenerative tears, including degenerative ‘root’ tears, is conservative. Exceptions include meniscal tears in younger patients after trauma, root tears, or any knee that causes mechanical symptoms such as locking or giving way.

Baker’s cyst 

Baker's cyst

A Baker’s cyst is a fluid collection at the back of the knee. It arises from the knee joint, so swelling of the joint will make the cyst bigger. Generally, bigger cysts put pressure on the joints, muscles, and nerves, leading to pain.

Typically, a Baker’s cyst is confirmed by an ultrasound. However, occasionally, for painful cysts, we drain the cysts using a needle under ultrasound.

Tendon and muscle injuries causing pain behind the knee

Tendon injuries often occur in runners due to overload. The tendons most likely to be affected include the hamstring on the inside (semimembranosus) or outside (biceps femoris). Rarely, a small tendon called the popliteus wrapping around the outside of the knee joint can become swollen and painful.

In addition, hamstring muscle tears can occur close to the outside of the knee. Usually, these tears occur about 5cm above the knee joint. Determining the exact location of the tear is essential, as location determines the time to return to sport.

Finally, a pulled calf muscle near the knee can also cause pain in this area.

Nerve damage 

Pinching nerves in the lower back (sciatica) or the buttock (piriformis syndrome) can cause pain radiating down the leg and into the back of the knee. However, pain isolated to the back of the knee is not usually associated with nerve damage.

DVT (deep venous thrombosis)

Similar to nerve damage, it is rare for deep venous thrombosis or DVT to cause pain at the back of the knee. Usually, pain from DVT extends to the calf and inner thigh. Frequently, the ankle and calf are swollen. However, some people have an increased risk of DVT, such as obesity, cancer, recent surgery, and long-haul travel.

Common questions related to pain behind the knee

Why is the back of my knee swollen? 

Generally, swelling at the back of the knee is due to a Baker’s cyst. However, Baker’s cysts are not usually painful. You must see your doctor if you experience severe pain and swelling behind the knee. Sometimes, large Baker’s cysts can become unbearable. Other causes include DVT or popliteal aneurysms.

What causes pain behind the knee and in the calf? 

If you experience pain in your knee and calf, you likely have a problem unrelated to the knee joint. Possible causes include nerve pain from the lumbar spine, piriformis, or DVT.

MRI of my knee didn’t show anything. What does that mean? 

A normal MRI scan doesn’t necessarily rule out all problems in the knee joint. Nonetheless, we would consider other causes, such as DVT or pain from the spine.

Final word from Sportdoctorlondon about pain behind the knee

Pain behind the knee is not straightforward. Some conditions can be life-threatening, such as a DVT. Other conditions may need further investigations and treatments. We suggest you see a sports medicine consultant for an accurate diagnosis and management plan.

Related conditions:

Dr Masci is a specialist sports doctor in London. 

He specialises in muscle, tendon and joint injuries.