Baker cyst


A fluid-filled lump behind the knee is called a Baker cyst. It results in a bulge and a tightness. A Baker cyst, also known as a popliteal cyst, can occasionally be painful. When engaging in physical activity, fully straightening or bending the knee, or both, the discomfort may intensify.

This cyst bears the name of the physician who initially reported it, as is common with many illnesses and conditions. Dr. William Morrant Baker came to the conclusion that these popliteal cysts were caused by fluid leaking out of a damaged knee joint in the mid-1800s.

A knee joint issue, such as arthritis or a cartilage tear, is typically what causes a Baker cyst. These ailments might result in the knee producing too much fluid.

Despite the possibility of swelling and discomfort brought on by a Baker cyst, relief is typically achieved by treating the underlying issue.


A Baker cyst might occasionally go unnoticed since it doesn’t hurt. If you do experience symptoms, they may consist of:

  • Pain in the knee
  • The knee becomes stiff
  • Unable to fully flex the knee
  • The leg or the part behind the knee becomes swollen at times

After exerting yourself or after a prolonged period of standing, the symptoms could be severe.

If you experience pain or swelling behind your knee, see a doctor. These symptoms might indicate a blood clot in a leg vein, even though it is improbable.


The knee joint relies on synovial fluid to lubricate its moving parts and reduce friction during leg movement. However, certain underlying conditions can cause the knee to produce an excessive amount of synovial fluid, leading to the formation of a Baker cyst at the back of the knee.

Some factors that may contribute to this include:

  • Physical injury to the knee that can result in cartilage tears.
  • Inflammation of the knee joint, which can be caused by various types of arthritis.