Baker cyst M71.2

Cystic protrusion of the joint capsule into the hollow of the knee.

Prolonged increase in pressure in the knee joint, especially in chronic inflammation with effusion formation. Baker's cysts occur mainly in chronic inflammatory rheumatic diseases, in chronic polyarthritis, but also in seronegative spondarthritis and arthroses of the knee joint.

The Baker cyst, which is located in the back of the hollow of the knee, is usually connected to the inner space of the anterior knee joint by a narrow channel. This channel can become misaligned like a valve mechanism. This prevents the synovial fluid from flowing back from the back to the front either completely or partially. Risk of rupture, whereby joint fluid can be pressed into the lower leg muscles. This leads to a severe irritation of the tissue with very severe pain and a strong inflammatory reaction with swelling and redness of the entire lower leg.

As a rule, the correct diagnosis can already be made as a gaze diagnosis and by manually examining the knee (examination with the hands). The exact location and extent of the cyst can be seen very clearly in the ultrasound image during arthrosonography. Arthrosonography is also successful in detecting the rupture and distinguishing it from deep vein thrombosis of the leg. For this purpose, an additional sonographic examination is best performed (colour Doppler sonography).

Phlebothrombosis (deep vein thrombosis)

The therapy of a Baker cyst is not necessary in every case. In the case of larger cysts or if there are complaints, especially if there is a risk of rupture, treatment should be carried out. In the past, Baker cysts were often removed surgically, often from the hollow of the knee. However, since the cause of the Baker cyst is the increased intra-articular pressure and since this is mainly due to an increased formation of synovial fluid in the anterior parts of the knee joint, the success of this surgical measure was usually only brief. Today, Baker cysts are normally no longer operated on from the hollow of the knee by means of a surgical procedure. Instead, one first tries to treat the usually underlying knee joint inflammation by means of a joint puncture and the intra-articular injection (injection) of glucocorticoids. If this is not successful in the long term, arthroscopy must be considered. The inflamed inner skin of the joint is then removed (synovialectomy), and if necessary, further measures are taken to eliminate any damage to the inner knee (e.g. meniscus damage, cartilage damage, torn ligaments).