Recognizing Baker's Cysts

The practice of massage therapy helps develop outstanding palpation skills for the practitioner. Many of these structural abnormalities may not even be painful. It is still important to be aware of those that are not painful because they may be an indication of an underlying pathology that could cause problems later on.

One such condition that may be evident during massage of the lower extremity is a fluid-filled cyst called a Baker's cyst or popliteal cyst that develops in the posterior knee region. Most Baker's cysts are benign, but they can cause pain and are frequently an indication of other pathologies so it is important to properly identify them.

Baker's cysts are the most common cysts found around the knee and the most common cysts lined with a synovial membrane anywhere in the body. They develop posterior to the knee joint and are usually found directly behind the medial femoral condyle between the medial head of the gastrocnemius muscle and the semimembranosus tendon. The cyst fills with fluid and becomes a palpable mass in the proximal posterior calf.

Baker's cysts may develop for a number of different reasons, but the cause is not always clear. There seems to be a correlation between the development of a Baker's cyst and the presence of other knee pathologies. For example, these cysts routinely occur after conditions such as osteoarthritis, rheumatoid arthritis, gout, meniscal tears, cruciate ligament tears, or osteochondritis dissecans have occurred in the knee. The reason they develop after these conditions is not entirely clear, but since the lining of the cyst is intimately connected with the joint capsule of the knee, irritation of the capsular tissues may have something to do with it.

The Baker's cyst has another interesting structural feature. Examination of the cyst reveals there is a one-way valve system that communicates between the capsule and the cyst. The cyst develops as a fluid-filled pouch of capsular tissue, but there is not a free exchange of fluid between the cyst and the internal knee structures. The one-way valve only lets fluid pass from the internal knee joint into the cyst. This is one reason for so much fluid accumulating in the area. As fluid develops within the cyst, it may press on other structures in the region and produce pain. Presence of the cyst behind the knee is also likely to prevent full flexion of the knee and may cause some discomfort or limitation to full extension.

There are a number of fluid-filled cysts that occur in different regions of the body, such as the ganglion cysts found around the wrist. A primary focus of treatment for these cysts is aspiration, or drawing the fluid out of the cyst. With Baker's cysts, aspiration is not performed because the fluid is much thicker and can't be drawn through the narrow diameter of a needle during aspiration. Treatment usually relies on conservative approaches such as rest from offending activities, thermal therapies including both ice and heat, and nonsteroidal anti-inflammatory medications (NSAIDS). The rationale for some of these approaches, such as heat or ice, is not entirely clear and is rarely given.

Since the Baker's cyst is often the result of some other pathology associated with the knee joint, it is important to address that underlying pathology. In many cases, the Baker's cyst will resolve on its own if the original problem can be resolved.

There is no benefit to treating a Baker's cyst with massage. Because it is a fluid-filled mass with a one-way valve, mechanical pressure on the cyst will not do anything to help the fluid move out of it and may, in fact, irritate the problem further. Most massage practitioners are cautious about pressure to the posterior knee region due to other delicate neurovascular structures in the region. This caution is warranted, as pressure behind the knee can damage these tissues.

Sometimes, more advanced practitioners may attempt treatment of some of the important muscles in this region, such as the popliteus and plantaris. Because the bellies of these muscles are only in the posterior knee region, they are difficult to treat in any other way. Putting further pressure on a Baker's cyst in this region could occur when attempting to treat one of these deeper knee muscles, and could aggravate the cyst. However, the palpatory skills of the massage practitioner frequently help to identify the tissue abnormality so the person can be referred to someone who can more accurately identify and treat the problem. Other conditions such as deep-vein thrombosis or popliteal aneurysms can also produce similar symptoms, and these problems are all serious enough to warrant referral to another specialist.