Introduction/Definition
The Baker cyst was first described in the 19th century by the English surgeon William M. Baker. It is also called knee joint ganglion or popliteal cyst. It is a sack-shaped sac-like sac of the bursa at the back of the knee joint, which occurs particularly frequently in children up to the age of 15 years.
It often occurs without symptoms, but can cause a feeling of tension in the hollow of the knee. In general, an observant and wait-and-see attitude applies in therapy, as the Baker’s cyst can recede of its own accord in the course of the child. Alternatively, an operation must be considered.
The association with rheumatism is rare. An X-shaped malposition of the legs (knock-knees) is more frequent. In addition to the real Baker’s cyst in children, there is the clinical picture of the so-called pseudocyst.
The cause is a joint disease or bursitis, as a result of which inflammatory fluid is formed. It can appear in the form of a sac of the bursa. – Thigh muscles (Musculsus quadriceps femoris)
- Thigh bone (femur)
- Thigh tendon (quadriceps tendon)
- Kneecap (patella)
- Patellar tendon (patella tendon)
- Patellar tendon insertion (Tuberositas tibiae)
- Shin bone (tibia)
- Fibula (fibula)
Symptoms
In most cases, the Baker’s cyst causes hardly any discomfort in the child. Pain may radiate to the thigh region, the back of the knee and the muscles of the calves. More common, however, is a feeling of tension in the hollow of the knee, which increases during physical exertion and then decreases again.
This is due to an increased fluid volume in the cyst. Usually the size of the cyst varies between a walnut and a hen’s egg. Movement restrictions can occur especially when the knee joint is bent.
The larger the size of the cyst, the more severe the symptoms may be in the form of pain and restricted movement. When palpating the cyst, a bulging elastic structure dominates, which should not be confused with a tumour. A possible complication is the bursting of the cyst, in which the fluid contained in the cyst passes into the tissue.
Symptomatically, the event is accompanied by increasing swelling and pressure-related pain. The symptoms are similar to the symptoms of deep vein thrombosis of the leg, which should be clarified diagnostically. If the fluid-filled tissue bag exerts pressure on a nerve, sensory disturbances up to paralysis can occur.
Cause
The exact cause of the Baker’s cyst in the child has not yet been clarified. The bag-shaped sac sacs appear spontaneously. It is assumed to be a congenital overproduction of the synovial fluid, which seeks the path of least resistance.
Since the joint capsule at the back of the knee joint is particularly flexible, a spherical bulge develops at this point. It forces its way through the muscle head of the calf muscle (M. Gastrocnemicus) and the tendon attachment of the semimembranous muscle (M. semimembranosus). Its occurrence occurs more frequently in boys before the age of 15.
In contrast to the pseudocyst of adults, the Baker’s cyst is less associated with rheumatic diseases than with an X-shaped malposition of the legs. Basic diseases such as rheumatism and arthrosis are therefore not among the causes in childhood. In children, a so-called ganglion can develop as a result of permanent irritation of the muscular tendon sheaths.
