Plica Syndrome of the Knee

An Unusual Cause of Knee Joint Pain

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Plica syndrome, sometimes called "synovial plica syndrome," is a condition of irritation of the tissue that is the inner lining of the knee joint.  Synovium is the type of tissue that forms the lining a joint.  The synovial tissue contains the joint space and helps to make the normal fluid that lubricates the joint.

The synovial plica are membranes that separate the knee into compartments during fetal development.

These plica bands normally shrink in size during the second trimester of fetal development. In adults, they exist as sleeves of tissue called "synovial folds," or plica. In some individuals, the synovial plica is more prominent and prone to irritation.

Plica Syndrome

The plica on the inner side of the knee, called the medial plica, is the synovial tissue most prone to irritation and injury. When the knee is bent, the medial plica is exposed to direct injury, and it may also be injured in overuse syndromes. When the plica becomes irritated and inflamed, the condition called plica syndrome results.

Diagnosis of plica syndrome is made by physical examination or at the time of arthroscopic surgery. Plica syndrome has similar characteristics to meniscal tears and patellar tendonitis, and these conditions may be confused. The most common signs of plica syndrome include:

  • Knee pain on the inner side of the joint
  • Tenderness directly over the medial plica
  • Swelling and warmth around the plica
  • Snapping and clicking when the knee is bent

X-rays of the knee are typically normal in a patient with plica syndrome.  An MRI may be done to help with the diagnosis, but this test is not a perfect method to diagnose this condition.

Treatment of Plica Syndrome

Plica syndrome is best treated by resting the knee joint and allowing inflammation to subside.  Treatments to reduce inflammation include ice application and anti-inflammatory medications. These measures are usually sufficient to allow the irritated plica to settle down. Occasionally, an injection of cortisone into the knee will be helpful.

If these measures do not alleviate the symptoms, then surgical removal of the plica may be necessary. This surgical procedure is performed using arthroscopic knee surgery, or a small camera, that is inserted into the knee along with instruments to remove the inflamed tissue. The arthroscopic plica resection has good results assuming the plica is the cause of the symptoms. Often a plica is seen on arthroscopic examination. Unless the patient's symptoms are consistent with plica syndrome, and the plica looks inflamed and irritated, the plica is usually left alone. Plica resection during arthroscopy is only performed if the plica is thought to be the source of symptoms.


Ewing JW, "Plica: Pathologic or Not?" J. Am. Acad. Ortho. Surg., Nov 1993; 1: 117 - 121.

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