• Introduction



• Anatomy

• Causes

• Symptoms

• Diagnosis

• Treatment

  Introduction

A popliteal cyst, also called a Baker's cyst, is a soft, often painless cyst on the back of the knee. A cyst is usually nothing more than a bag of fluid. These cyst occur most often when the knee is damaged due to arthritis, gout, an injury, or from inflammation of the joint lining. Treatment of the cyst is most successful when the underlying cause of the cyst is also treated. Otherwise, the cyst can reoccur.

Rarely, the cyst can cause pressure on blood vessels causing swelling or other problems in the leg. A ruptured popliteal cyst can be very painful. The symptoms caused by a popliteal cyst can mimic more serious problems. Therefore, careful clinical evaluation is important.

The purpose of this information is to help you understand popliteal cysts:
The nature of disorder and the normal anatomy of the knee
the signs and symptoms of the disorder
the treatments available to you now and later
what you can expect from those treatments
what you can expect long-term if you have this disorder

In order to understand what is happening with your knee joint, you need to understand the basics about the normal anatomy of your knee. This includes becoming familiar with the various parts that make up the knee. Also, you should understand the function of these parts, that is, how they make your knee work. Keep in mind that no one is going to give you a test, but the more you know, the more you will be able to talk with your doctors and healthcare team in words that will help them better understand your particular disorder. It will also help you understand what they are telling you about your particular problem.

Anatomy of the Knee Joint

A joint is formed where two or more bones meet. The knee is a hinge type joint and is formed where the thighbone (femur) meets the shinbone (tibia). The thighbone is rounded on the end and rocks back and forth on the flat surface formed on the end of the shinbone. A smooth cushion of articular cartilage covers the surface ends of both of these weight-bearing bones. The articular cartilages are kept slippery by joint fluid made by the synovial membrane (joint lining). Since the cartilage is smooth and slippery, the bones move against each other easily and without pain.

In addition to bones, the knee joint is also made of "soft tissues". These soft tissues include ligaments, tendons, muscles, and blood vessels. Tendons and ligaments are connective tissue. Bones are attached (connected) to bones by ligaments. Muscles allow us to bend and straighten the bones in our knee joint. Muscles are attached to bones by tendons. Nerves send electrical impulses to muscles, which make them, contract and relax causing the joint to bend and straighten. Blood vessels carry needed oxygen, nutrients, and fuel to the muscles to allow them to work normally - and to heal when injured.

Causes

A popliteal cyst forms when the joint lining produces too much joint fluid. The extra fluid leaks or pushes through the joint lining and forms a cyst. The cyst often "sticks out" on the back of the knee between two muscles. If the cyst ruptures, it can cause pain and swelling of the calf. A ruptured popliteal cyst is important because its symptoms are just like a much more serious problem called thrombophlebitits. Therefore, it is important to determine right away the cause of the pain and swelling in the calf.
 

Symptoms

Symptoms are things that you feel. The symptoms caused by a popliteal cyst are usually mild. You may have aching or tenderness with exercise or your knee may give way. Sometimes, there is pain from the underlying cause of the cyst, such as arthritis, an injury, or a mechanical problem with the knee. Along with these symptoms, you may also see or feel a bulge on the back of your knee. Anything that causes swelling of the knee and more fluid in the knee joint can make the cyst larger. It is common for a popliteal cyst to swell and shrink over time.

Sometimes a cyst will suddenly rupture, or burst underneath the skin, causing a lot of pain and swelling in the calf. The fluid inside the cyst simply leaks into the calf and is absorbed by the body. In this case, you will no longer be able to see or feel the cyst. However, the cyst will probably return in a short time.
 

Diagnosis

You doctor will ask you to tell him the history of your problem, such as how long have you had the problem, have you noticed it getting worse, and how has it kept you from doing your daily activities, what makes it worse, or what makes it better. He will ask if you have any pain. Then he will examine your knee and leg. He will ask you to bend and straighten your knee to see if he can feel or see the cyst. Most often, a physical exam is all that is needed to diagnose a popliteal cyst. Unless the cyst has ruptured, further testing is usually not needed.

If the cyst has ruptured, additional test will be needed. Regular x-rays will not show the cyst since it is a soft tissue and regular x-rays show mostly bones. A cyst can be seen with a sonogram, or arthroscopy.
 

Treatment

There are two types of treatment for popliteal cysts: surgical and non-surgical. Whether or not the cyst has ruptured, how painful the cyst has become, or how much it interferes with the normal use of your knee will determine which is the best course of treatment for you. In adults, the treatment is most often non-surgical. If surgery is needed, it is usually done on an out patient basis. Unless there is a lot of discomfort from the cyst surgery is rarely indicated.
Non-surgical:

Drawing the fluid out with a needle and syringe can reduce the size of the cyst. Then, cortisone can be injected into the affected area to reduce inflammation. Non-surgical treatment also includes rest and keeping your leg propped up for several days. If non-surgical treatment fails, then complete removal of the cyst may be needed. Many people - once they are reassured that the cyst is not dangerous - simply ignore the problem unless it becomes very painful.



Surgical Treatment:

The goal of surgery is to remove the whole cyst and repair the hole in the joint lining where the cyst pushed through.

Anesthesia

Surgery can be slow and take over an hour to complete. Surgery is usually done under a general anesthetic, where you are completely asleep during surgery, or spinal anesthesia, where the lower half of the body is numbed. With spinal anesthesia you may be awake during the surgery, but you won't be able to see the surgery.

Surgery

Once you have anesthesia, your surgeon will make sure the skin of knee your is free of infection by cleaning the skin with a germ killing solution. An incision will be made in the skin over the cyst. The cyst is located and then separated from the surrounding tissues. The area of the joint capsule where the cyst appears to be coming from is identified. A synthetic patch may be sewn in place to cover the hole in the joint capsule left by the removal of the cyst. Special care is taken not to damage nearby nerves and blood vessels.

Your knee will be bandaged with a well-padded dressing and a splint for support. Your surgeon will want to check your knee within 5 to 7 days. Stitches will be removed after 10 to 14 days. Most of your stitches will be absorbed into your body. You may have some discomfort after surgery. You will be given pain medicine to control the discomfort you have.

You should keep your knee propped up for several days to avoid swelling and throbbing. Keep it propped up on a stack of pillows when sleeping or sitting up. Take all medicines exactly as prescribed by your physician. Be sure to keep all follow up appointments.

Complications

You should expect complete healing without complications in about 4 weeks. The most common possible complication after surgery is infection of the incision. If infection occurs, your surgeon may prescribe antibiotics to fight infection or surgery may be needed to drain the infection. After surgery, keep 24-hour phone numbers handy. Call you surgeon's office if you feel your knee is not healing as it should. Check your incision as instructed by your doctor. If you think you have a fever take your temperature. If you have signs of infection or other complications, call your surgeon right away.

These are warning signs of infection or other complications:
pain in your knee that is not relieved by your medicine
smelly discharge coming from your incision
red, hot, swollen incision
chills or fever over 100.4 F
you notice bright red blood coming from you incision
if you have side effects from your medicine

Baker's cyst form very near the major nerve and blood vessels of the leg. It is possible that these structures can be injured during surgery. If an injury happens, it can be a serious complication. Injury to the nerves can cause numbness or weakness in the foot and lower leg. Injury to the blood vessels may require surgery to repair the blood vessels.

In addition, it is uncommon but possible that another cyst can occur.

Rehabilitation

After your surgery you can resume daily activities and work as soon as you are able. Your doctor may want you to use crutches or a cane for awhile. Avoid vigorous exercise for 6 weeks after surgery. You should be able to resume driving 2 weeks after surgery. You may need a short course of physical therapy to regain the strength in your leg.

Summary

While a popliteal cyst is not a life-threatening problem, a ruptured cyst can mimic one and can be cause for concern until a diagnosis is made. It is important to know that these cysts are always limited to the knee. The cysts are not cancerous and will not become cancer.

 
Removal of the entire cyst, if necessary, will usually give a very good result. The cure is often permanent, but preventing further cyst depends a great deal on the success of treating the underlying cause.
 

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