The synovial plica are membranes that separate the knee into compartments during foetal development. These plica normally diminish in size during the second trimester of foetal 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.
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 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 is made by physical examination or at the time of arthroscopic surgery. Plica syndrome has similar characteristics to meniscal tears and patella tendonitis and these may be confused. An MRI scan may be done, but it is often not terribly helpful in the diagnosis of plica syndrome.
Symptomatic plica syndrome is best treated by resting the knee joint and anti-inflammatory medication. These measures are usually sufficient to allow the inflammation to settle down. Occasionally, an injection of cortisone into the knee may 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 an arthroscope, 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 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 cause of symptoms.