Baker's Cyst

A Baker's cyst (or popliteal cyst) arises on the back of the knee and is associated with an abundance of synovial fluid overstretching the joint capsule. It is thought to affect a significant amount of people who are suffering from another knee condition.


A Baker's cyst is regularly asymptomatic aside from the noticeable lump or bump behind the knee (though sometimes even the bump is small enough to avoid detection). The lump will generally feel like a sphere the size of a golf ball filled with liquid, and is unlikely to be sore or painful to the touch. However, in some cases the cyst may affect movement of the knee joint, such as leg bending and straightening. Such motions might begin to become harder to achieve, with the joint seeming inflexible, or they might simply be accompanied by pain caused by the cyst's interaction with the movement. Aching might be present after exercising, along with a pressure at the back of the knee.

The cyst can become ruptured, either naturally, by accident or due to unsuitable intervention such as excessive squeezing or pricking the cyst with a needle. If this occurs then the fluid previously contained within the cyst might flow along the leg. Possible symptoms are analogous to those of a deep vein thrombosis and include bruises, redness, calf inflammation and pain.


Any knee injuries sustained around the same time period as the Baker's cyst can involve considerable swelling and thus provoke the condition. In sports, knee injuries are often caused by sudden hard impacts, whether this is from a ball, bat or projectile, a tackle or strike from a fellow competitor, or the result of a falling accident. Osteoarthritis and other forms of arthritis are particularly common causes of the cyst for older sportsmen and women, while the same is true for tearing of the meniscus cartilage in young athletes. Baker's cysts are most widespread in young children and middle-aged adults.

Medical Treatment

Due to the probability of the cyst being caused by an existing injury, it is important to consult a doctor to check for other conditions and receive appropriate treatment. Meanwhile the Baker's cyst is relatively likely to heal itself with little intervention. A doctor might drain its fluid. You should rest from any activity that causes aching or worsens the cyst until it disappears. Some cases will require surgery or other medical treatment due to an associated condition or the severity of the cyst. This may put you out of action for up to 3 months. Cysts can occasionally reappear.

Please note that a lump on the rear of your knee is not guaranteed to be a Baker's cyst, and should always be examined by a doctor to assess whether it is a more serious condition such as a tumour.

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