Symptoms
The symptoms of a Baker’s cyst in the knee are constant or recurring pain and a swelling, which can be palpated in the hollow of the knee to varying degrees in patients. Furthermore, patients often complain of a feeling of pressure in the hollow of the knee, which is perceived as a diffuse pulling/tensioning sensation in the back of the knee when the knee is stretched or bent. Depending on the size of the cyst, movement is restricted during knee flexion, and the feeling of pressure increases.
The perceived pain usually increases when the knee is strained (e.g. during long running or sports activities). The Baker’s cyst in the knee can also constrict nerve and vascular pathways. This can cause numbness, circulatory problems or paralysis. If the cyst exerts pressure on the leg veins, the reduction in the blood flow velocity can lead to the formation of a thrombosis (the formation of a blood clot in the blood vessel).
Baker’s cyst burst – now what?
It is rather rare for the cyst to burst (rupture). If the cyst becomes too large or the pressure created by the fluid increases, the cyst wall may rupture – usually when the knee is moved. Often patients notice the bursting of the cyst by an increase in the intensity of pain.
If the Baker’s cyst ruptures in the knee, inflammation may occur in the knee and surrounding areas with inflammatory symptoms such as pain, redness, swelling and overheating. The spread of the inflammation is due to the fact that synovial fluid from the cyst passes into the surrounding tissue. The fluid can also spread from the knee to the lower leg and up to the foot.
In these tissues there is finally also an increase in pressure and inflammation, which can constrict and damage surrounding structures such as nerves and blood vessels. This can have serious consequences and should be treated as soon as possible. It is also important to distinguish the burst cyst from a leg vein thrombosis. This is done by the doctor using duplex sonography (a special ultrasound examination). During this examination, the blood flow in the veins is shown and a thrombosis is ruled out.
Do what?
In most cases the cyst will regress on its own. How long this takes and whether it happens at all cannot be said. In case of pain and restricted movement, a doctor should be consulted. This doctor will examine the knee using ultrasound and other imaging techniques (MRI of the knee), diagnose the cause and suggest a suitable therapy. In any case, if there is swelling in the popliteal area, where it is not certain whether it is a cyst, a thrombosis should be ruled out.
