Knee Pain–Unraveling the Mysterious Meniscus
By Scott Stubbs, M.D.
Summertime is here! This seems to be a favorite season for many with a big increase in outdoor activity. Softball leagues, water skiing, and just good ole "pick-up" games at parks and driveways around town are heating up fast. Often this time of year, a painful knee joint can heat up just as fast as a summer afternoon in Oklahoma.
Knee pain is probably the most common complaint I see in the office. The most common acute problems affecting the knee are sprains, strains and tears of the soft tissues of the knee joint — the ligaments, tendons and cartilage or menisci. These structures may be injured as a result of a single incident or by repeated minor trauma. Often times the minor, repetitive trauma can result in an injury just as debilitating as a single, acute event.
The meniscus is a structure in the knee that is particularly prone to such injury. The knee has two menisci (plural for meniscus), one on the inner, or medial, side and one on the outer, or lateral, side. These structures are a specialized type of cartilage that is interposed between the bones in the knee. They function to help distribute and absorb the forces placed across the joint. This reduces the focal stress placed on the other type of cartilage in the knee that coats the ends of the bones, the articular cartilage.
The knee has been called a hinge type joint but viewing it as a simple hinge is too simplistic. There are subtle amounts of rotation (twisting) and translation (sliding) that occur with normal use. There are even greater amounts of these motions that occur during summertime athletic activities. It is usually these motions, or the excess of them, that puts a meniscus in harms way.
When a portion of the meniscal tissue gets pinched between the bones awkwardly, failure of the collagen fibers that make up the microstructure of the meniscus can occur. This can be in the form of a very noticeable one time event where a "pop" is felt or even heard. Often, however, it is the small, repetitive episodes of injury that eventually compromise the meniscus enough for symptoms to occur without any memorable injury that took place.
Symptoms of a torn meniscus are joint pain and swelling. Sometimes mechanical symptoms of catching or even locking of the knee can occur. A fluid collection inside the joint called an effusion is a very specific sign that internal injury may be present. The fluid, or "water on the knee", is produced by the lining of the joint in response to injury or disease. The fluid is a sign of a problem and not the problem in and of itself. The pain from a torn meniscus may be worsened by fully flexing and/or twisting the knee which puts stress on the meniscus. Squatting, such as a catcher’s stance in baseball, reproduces this type of motion and is often impossible without significant discomfort.
Unfortunately, these cartilage tears have poor ability to heal themselves. The tissue has a very limited blood supply which is needed for our body to repair itself. Furthermore, once a tear or weakness in the structure is present, it tends to progress if repeated stresses to it continue. These stresses may even be in the form of simple activities of daily living that would normally not be a problem for the knee to withstand.
Because of the inability of our body to repair these injuries, treatment of a meniscus tear is often surgical. Arthroscopic (small incisions and telescopic instruments) surgery is a very useful and successful tool in treatment. The tear can be evaluated and treated at the same setting with minimal trauma to the surrounding tissues. The procedures are usually done in an outpatient setting with quick recovery times.
In some instances, the tear may be repairable depending on the configuration and location of it. This is an advantage in the long run since the tissue remains in place to perform its function to protect the joint surfaces and prevent degenerative arthritis. Repair of a meniscus tear significantly extends recovery time and certain restrictions on activities are required to protect the tissue while healing occurs. This usually means a period of several months before a return to athletic or strenuous work activities is possible.
Most often, the tear is not repairable and the treatment is to excise, or take out, the torn portion. This usually relieves the pain, swelling and mechanical symptoms in as little as days to weeks. The damaged portion is the only part removed. Attempt is made to retain as much of the normal tissue as possible. Again, this is important because of the joint protecting function of the meniscus. Severe injuries where a large majority of the meniscus is lost can lead to rapid degenerative changes or osteoarthritis of the involved portion of the knee. Luckily, it is usually a relatively small portion of the tissue and most people have very good chances to regain normal function of the knee with the expectation to return to all activities.
So have a fun and safe summer but pay attention to the signals your knees are sending you. Pain is an important message from the body that shouldn’t be ignored. If the summer heat seems to be emanating from your knee rather than the weather, seek a professional opinion for a speedy and healthy return to all that summer fun.