Today I will cover cysts and spurs - “Baker's cysts” and bone spurs specifically.

Some of the most common questions I am asked as an orthopedic surgeon are about bone spurs. I think that each patient has an idea of what a bone spur actually is. Bone spurs are actually the result of a problem, not so much the cause of a problem.

Specifically, bone spurs are caused by arthritis. They do not cause arthritis. Arthritis is nothing more than the cartilage on the end of the bone wearing down similar to the tread on a tire. When the cartilage wears down, the underlying supportive bone senses more force and pressure going across it because the cartilage is wearing thinner and can't absorb as much force and pressure.

As the bone starts to experience more and more force, it actually does a smart thing. It tries to distribute that force over a larger surface area. The way that it does that is it grows outwards or to the periphery of joints, forming prominences called osteophytes, otherwise known as spurs.

In regard to the knee joint, they seem to develop more on the inner or outer side of the joint; though more commonly toward the inner side of the joint. Just the fact that they stick out further can cause mechanical pain. Other times they can break off and become loose bodies or joint mice floating around the joint causing mechanical symptoms such as locking and catching. In and of themselves, however, the spurs aren't the actual problem; it is the underlying arthritis that is the problem.

Going in and trimming out the spurs isn't going to get rid of the underlying problem, which will only return. If they are loose and floating around in the knee joint, that certainly is an indication to go in and take them out surgically. Sometimes we do have to shave them down or remove them if they are causing mechanical or range of motion (ROM) problems. What really needs to be considered is how to treat the underlying problem of the arthritis. That may be in the form of a joint replacement.

Another commonly misconceived medical condition that I see is a Baker's cyst. Patients often come in stating, “My doctor tells me I have a Baker's cyst.” Once again, Baker's cysts are usually the result of a problem and not the cause. A Baker's cyst results from the following scenario. There is a bursa (sac) in between the muscles of the back of the knee. It communicates with the posterior aspect (back side) of the knee joint. A bursa is a little, thin, fluid-filled sac that lubricates two structures; in this case, two muscles, from having any friction between them.

If a process is going on inside the knee that is causing the knee to produce more fluid than normal, every time the patient bends the knee the fluid gets pushed towards the back of the knee and since it has nowhere to go, it can push right through the opening into the bursa and fill up the bursa similar to filling up a water balloon. “Going in and taking out the cyst” is not necessarily a good surgical option, in that it doesn't get rid of the actual problem, i.e. there is something going on inside the joint that is causing it to produce more fluid.

What can cause this? Things such as arthritis can cause inflammation of the joint, which causes increased fluid production, which can lead to a Baker's cyst formation. A meniscus/cartilage tear, rheumatoid arthritis, an infection, an injury or anything that causes the knee to produce more fluid and/or swell up with fluid can lead to a Baker's cyst.

The vast majority of time, if we can turn the fluid production back down to a normal level, the fluid in the cyst will reabsorb and the cyst will go away on its own. Sometimes that does require surgery, i.e. an arthroscopy to remove a torn meniscus cartilage, or even a total knee replacement to basically remove the arthritic surfaces.

I am hopeful this clarifies the many common misconceptions associated with these terms.

Dr. Marc P. Pietropaoli is a board certified/fellowship trained

orthopedic surgeon/sports medicine specialist and is president of Victory Sports Medicine & Orthopedics in Skaneateles.