The medial plica syndrome is an interesting problem that occurs when an otherwise normal structure in the knee becomes a source of knee pain due to injury or overuse. The diagnosis can sometimes be difficult, but if this is the source of your knee pain, it can be easily treated.

Anatomy

What and where is a plica, and what does it do?

The word plica is simply an anatomic term used to describe a fold in the lining of the knee joint. Imagine the inner lining of the knee joint as nothing more than a sleeve of tissue. This sleeve of tissue is made up of synovial tissue, a thin slippery material that lines all joints. Just like tailors build in extra folds of material at the back of sleeves on a shirt to allow for motion without restricting the motion of the arms, the synovial sleeve of tissue has folds of material that allow movement of the bones of the joint without restriction. There are actually four plica synovial folds in the knee, but only the one on the medial side seems to cause trouble. This structure is called the medial plica. The medial plica attaches to the lower end of the kneecap and runs sideways to attach to the lower end of the femur at the side of the knee joint closest to the other knee. Most of us (50-70%) have a medial plica, and it doesn't cause any problems whatsoever.
 

Causes

How does a plica cause problems in the knee?

Plicae cause problems when they are irritated. This can occur over a long period of time, such as when the plica is irritated by certain exercises or repetitive motions. Activities that repeatedly bend and straighten the knee - such as biking or use of a stair stepper machine can irritate the medial plica and cause plica syndrome.

Injury to the plica can also happen suddenly, such as when the knee is struck in the area around the medial plica. This can occur from a fall or possibly hitting the knee on the dashboard during an automobile accident. This injury to the knee can cause the plica, and the synovial tissue around the plica, to swell and become painful. The initial injury may lead to scarring and thickening of the plica tissue later. The thickened, scarred plica fold may be more likely to cause problems later.

Symptoms

What do problems from a plica feel like?

The primary symptom caused by the medial plica syndrome is pain. There may also be a snapping sensation as the knee is bent. This is due to the rubbing of the thickened plica over the round edge of the medial femoral condyle. There is usually tenderness over the area where the plica is located. In thin people, the tissue that forms the plica may be actually be felt as a tender band underneath the skin. If the irritation from the plica is particularly bad, there may be swelling in the entire knee.
 

Diagnosis

How is this problem identified?

Diagnosis begins with a history and physical. The examination will try to determine where the pain is located and whether or not the band of tissue can be felt. X-rays will not show a plica. X-rays are mainly useful to determine if other conditions are present if there is not a clear cut diagnosis. If there is a uncertainty in the diagnosis following the history and physical examination, or if other injuries in addition to the plica syndrome are suspected, a MRI scan may be suggested. The MRI (Magnetic Resonance Imaging) machine uses magnetic waves rather than x-rays, to show the soft tissues of the body. With this machine, we are able to "slice" through the area we are interested in very clearly. Usually, this test is done to look for injuries, such as tears in the menisci or ligaments of the knee. This test does not require any needles or special dye, and is painless. Most cases of plica syndrome will not require special tests such as the MRI scan.

If the history and physical examination strongly suggest that a plica syndrome is present, then arthroscopy may be suggested to confirm the diagnosis and treat the problem at the same time. Arthroscopy is a type of an operation where a small fiberoptic TV camera is placed into the knee joint, allowing the orthopedic surgeon to look at the structures inside the knee joint directly. The arthroscope allows your doctor to actually look into the knee joint and see the condition of the whole knee and see if an inflamed plica exists.

Treatment

What can be done for a plica syndrome?

The majority of people with plica syndrome will get better without surgery. The primary goal of treatment of the inflamed plica is to reduce the inflammation. This may require reducing your activity level - staying off the stationary bike or stairstep machine, for instance. Anti-inflammatory medications such as ibuprofen or aspirin may be suggested by your doctor to reduce the inflammation. Ice packs, or ice massage, can help reduce the inflammation and swelling in the area of the plica, and may be suggested by your doctor or physical therapist. Ice massage is an easy and effective way to provide first aid. Simply freeze water in a paper cup. When needed, tear off the top inch, exposing the ice. Rub three to five minutes around the sore area until it feels numb. A cortisone injection into the area of the plica, or simply into the knee joint may quickly help to reduce the inflammation around the plica. Cortisone is a powerful anti-inflammatory medication, but it should be used sparingly inside of joints. There is always a risk of infection associated with injections into any joint.

If all of the non-surgical attempts to reduce your symptoms fail, surgery may be suggested. Usually, the arthroscope is used to remove a plica. Arthroscopy is a surgical procedure that is done as an outpatient procedure. A small TV camera is inserted into the knee joint through small 1/4 inch incisions. Once the plica is located with the arthroscope, small instruments can be inserted through another 1/4 inch incision to cut away the plica tissue and remove the structure. The area where the plica is removed heals back with scar tissue. There are no known problems associated with not having a plica, so you won't miss the structure. Usually, there is very little rehabilitation after surgery to remove a plica and you will probably be on your feet immediately after surgery.