A Baker’s cyst is a large swelling located on the back of the knee, caused by an irregular collection of sinovial fluid. A Baker’s cyst, named after the physician who first described the condition, is usually harmless and goes away on its own. However, a Baker’s cyst can cause pain and discomfort if it continues to enlarge or ruptures. Caused by injuries, torn cartilage, infection, or arthritis, Baker’s cysts usually occur in elderly men or in young children, and in extreme instances have to be drained or surgically removed.
The knee is what is known as a hinge joint, entirely enclosed in a tough capsule that is lined with a membrane and filled with a lubricating agent called sinovial fluid. There are sacs and capsules of this fluid in the knee as well; they help to alleviate friction between tissues when you move your knee and these are called bursae sacs. Sinovial fluid circulates through the knee, passing in and out of these sacs. The amount of fluid going in and out of these sacs is regulated by a valve-like system between the knee and bursa sac located in the rear of the knee. This particular sac is the popliteal sac. Sometimes, when the knee is injured, it will produce too much sinovial fluid, causing the popliteal bursa to fill and expand, like a balloon filling with water. This forms a Baker’s cyst. The inflammation that results from torn cartilage and arthritis can cause an excess of sinovial fluid and contribute to a Baker’s cyst. In many adults, especially those with degenerative arthritis, a Baker’s cyst can form when the knee capsule herniates, or pushes through its protective membrane and into the back of the knee, filling up with fluid. It is important to realize that a Baker’s cyst is not a tumor nor cancerous in nature.
Often, you will experience no symptoms with a Baker’s cyst, but as it grows in size you may feel a feeling of pressure on the backside of your knee joint. It can ache and hurt constantly and restrict the mobility of the knee joint. When you stand up, you will notice an obvious lump in the region, and a sensation of tightness when you straighten your leg. A Baker’s cyst will go away on its own, but years may pass before it is totally gone. However, if a Baker’s cyst swells to the point that it ruptures, the sinovial fluid can leak into the area of the calf, and cause quite a bit of pain in the knee, swelling, and redness in the calf. This will closely mimic the symptoms of a blood clot in your leg, which is a very serious condition.
If you notice the telltale swelling on the back of your knee joint associated with a Baker’s cyst, contact your physician. They will want to immediately rule out other, more serious things such as a blood clot or an aneurysm. They will perform a physical exam on your leg and look at your medical history to see if something in it suggests that a Baker’s cyst is likely or possible. Although an X-ray will not show a Baker’s cyst, it will show other potential causes of such swelling. An MRI can show a Baker’s cyst as can an ultrasound examination. A procedure as simple as shining a bright light through a Baker’s cyst can show that there is nothing in it but fluid, helping your doctor reach a conclusion on the nature of the problem.
The treatment of a Baker’s cyst depends on its size, its cause and whether it is painful and causing you problems or not. When arthritis is the reason behind a Baker’s cyst, your doctor may place you on anti-inflammatory medications such as ibuprofen and aspirin to reduce pain and swelling. You may be advised to cut down on your physical activity for a while. A large and painful Baker’s cyst may require physical therapy such as wrapping it in ice or a compression wrap. The fluid may need to be drained from the Baker’s cyst using a large syringe, a procedure called needle aspiration that is not as painful as it sounds. Even the draining of fluid from a large Baker’s cyst does not guarantee that it will not return, and a cortisone injection to lessen the amount of sinovial fluid being manufactured in your knee can make a Baker’s cyst smaller, but likewise can not insure that it will not come back.
When torn cartilage is the culprit behind a Baker’s cyst, you may need surgery to repair it. In instances of osteoarthritis, when a Baker’s cyst is so large and persistent that it won’t go away and hinders mobility and movement, it may have to be surgically removed. In the Baker’s cysts that form on the back of children’s knees, a wait and see attitude is usually taken, as the vast majority of these disappear o
