Baker's cyst.

Baker's cyst. Swelling in the area behind the knee joint

Apart from marked functional impairment, pain and disease localised in the knee joint, a large number of patients complain of localised swelling in the area behind the knee joint (popliteal space), with more or less severe impairment caused by the local bulging.

 

What is a Baker's cyst?

Image (left): Popiliteal space showing the typical location of the cyst. Image (right): Knee viewed from the side - displacement of blood vessels and nerves

Image (left): Popiliteal space showing the typical location of the cyst. Image (right): Knee viewed from the side - displacement of blood vessels and nerves

A Baker's cyst is a cavity lined with mucous membrane and filled with a gelatinous fluid, located in most cases on the inside of the space behind the knee (Latin: popilitea, as a result of which a Baker's cyst is also known as a popliteal cyst). The cyst extends from the capsule of the knee joint between the lateral muscles and is connected to the joint via a stalk-like structure. The cyst was first described by William Morrant Baker, a surgeon from London (1836 - 1896).

 

What are the symptoms of a Baker's Cyst?

Patients complain of a localised, firm, elastic, in most cases non-inflammatory, non-painful area of swelling at the back of the knee joint, commonly towards the inside and extending in the direction of the foot. The swelling will prevent the knee from being bent to its fullest extent and is often associated with localised impaired function or pain in the knee joint itself. Tearing of the cyst will result in diffuse swelling over the entire calf with increased tenderness, accompanied by an inflammatory clinical picture with redness and excessive warmth evident to a greater or lesser extent.

 

Causes. How does a Baker's cyst develop?

A baker's cyst may be caused by a defective meniscus.

A baker's cyst may be caused by a defective meniscus.

Irritation of the knee joint can cause more knee fluid (synovial fluid) to collect in the knee. This can make the inner skin of the knee (synovial membrane) protrude out through the relatively thin, incomplete, flexor side of the joint capsule so that a synovial sac develops. Muscles are present on the side of the cyst´s stem that press the tissue together and act as a valve. The synovial fluid is unable to flow back into the knee joint. The cyst gets bigger and is more of a hindrance. In extreme cases, local inflammation in the calf (similar to a thrombosis) can cause the cyst to burst.

 

Concrete causes for irritation in the knee joint could be:

  • Rheumatic inflammation of the joint
  • Following bacterial inflammation in the knee
  • Mechanical irritation caused by damage to the meniscus, free joint bodies, folds in the mucous membrane, ligamentous instability, cartilage degeneration, knee cap instability
 

Therapy & Rehabilitation

If the Baker's Cyst reaches a certain size or leads to irritations of nerves and vessels, it must be removed.

Treatment & Rehabilitation

Specialised Clinics

Our specialised clinics and hospitals for the treatment of Baker's Cyst and knee diseases at a glance.

Specialised Clinics