Understanding pain behind the knee starts with understanding the structure of your knee. Your knee is composed of two three bones: the femur, tibia and patella or kneecap. On the outside of the knee lies the fibula, the small thin bone of the lower leg. The internalmost part of the knee joint is made of cartilage on top of the femur and tibia bone. This cartilage prevents the two bones from rubbing together and wearing down the actual bone underneath them. Ligaments surround this basic structure, as do muscles and tendons. One of the most common reasons for pain behind the knee is mechanical breakdown of any of these anatomical structures in the knee itself.

Pain behind the knee is only one of the symptoms that can be felt in the knee when something goes wrong in this part of the body. There could also be pain in the knee when bending the knee or extending it, pain in the knee during rest or during activity, and water on the knee, too. In many cases, the knee can swell from inflammation, and in some cases, it may swell to twice its regular size.

What causes pain behind the knee ?           Pain Behind Knee

There are many cases of pain in back of knee, and the most common are baker’s cyst, tear in the meniscus, injuries to the hamstring, patellofemoral syndrome, and tumor.

Baker’s Cyst

It someone experiences a tear in the cartilage of the knee or has arthritis, it’s possible that fluid can fill up in the back of the knee in an area called popliteal space. This is called a Baker’s cyst. The extra fluid fills up the compartment within a cyst-like structure and creates pain in back of knee. Cysts are usually drained with a medical process called aspiration where a needle is inserted into the cyst and the fluid is “vacuumed” out.

There are other methods that a baker’s cyst is drained. For example, by bandaging the area, it’s possible to compress the cyst, forcing the fluid out. Another method is by using ice to decrease the swelling in the knee, and a final one in administering corticosteroids, which are well-known for their ability to decrease inflammation. Once the inflammation is reduced, it’s possible that the body will reabsorb the fluid of the cyst.

The reason why doctors are concerned about Baker’s cyst is because it may rupture if stressed from walking or other activity. A rupture will be followed by very sharp pain behind the knee. The swelling could involve the lower part of the leg as well as just the knee.

Tear in the Meniscus

The meniscus is cartilage in the knee. If it tears, then the body has to overcome a lot to get the area to totally recover. The meniscus doesn’t receive much blood supply, and if it tears, how can it heal without a blood supply bringing in oxygen and nutrients to start the healing process? A tear in the meniscus causes pain behind the knee. Besides this, a tear can also lead to the development of arthritis later on in life.

Surgery is the treatment that doctors prefer, although the pain in back of knee will continue for quite some time after surgery until the knee heals.

Injuries to the Hamstring

The hamstring muscles are located in the back part of the thigh and end in a common tendon. If a sudden shock is felt on the muscle, there will be pain behind the knee. There will also be swelling due to inflammation.

Injuries to the hamstring are treated with RICE (rest, ice, compression, and elevation). Depending on the extent of the muscle injury, surgery may be recovered. Unfortunately, the pain may continue for a few months until healing is complete.

PatelloFemoral Pain Syndrome Can Cause Pain Behind the Knee

Cyclists are most prone to develop this cause of pain behind the knee. The repetitive motion of pedaling can cause the patella to get out of alignment and fall “off track” the tendon. This type of pain behind the knee can also result from running. In this disorder, the answer is strengthening all the muscles surrounding the knee – the quadriceps, the hamstrings and the buttock muscles.


Although tumors are rare, they can be a cause of back of knee pain. Generally tumors found in the location of the back of the knee usually affect only one knee, not both. The difference between other cases of pain behind the knee and ones caused by a tumor is that the tumor often causes constant pain, not just pain when the knee is bent. The pain may even wake up the person at night during sleeping.

Don’t diagnose these conditions on your own. Your doctor will be able to use imaging techniques to see what is going on inside your knee and rule out each one of these individually. When he initially takes a history and examines you, he’ll also be able to rule out some of these causes of pain behind knee.

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