Knee > Plica Syndrome

What are Plicae?

Plicae are thin walls of fibrous tissue, which are thickenings of the lining of the knee joint, or synovium. In a developing fetus, the plicae separate the three compartments of the knee. In about one-third of the population, by the fourth month of fetal development the plicae combine to form one large protective cavity for the knee. For the majority of people, however, some or all of the plicae remain in the knee joint.

Plica syndrome is an irritation of the plicae that occurs over time due to repetitive motion, or an acute injury, which can cause the plicae to swell, thicken, and ultimately cause pain. In some cases, plicae can become caught between the kneecap and thighbone (femur), causing pain and discomfort. Or, they can scrape the surface of the articular cartilage that cushions the ends of the shinbone and thighbone, which can lead to arthritis.


Repeated bending and straightening of the knee, such as the motions used in cycling or using a stair-climbing machine, can contribute to plica syndrome. So can a blow to the inside (big-toe side) of the knee, where the medial plica is located.


It is often difficult to determine whether removing the plicae surgically makes a significant difference in knee function. The proof may not come until several months later. However, surgical removal of plicae has not been shown to adversely affect knee strength and stability. In some instances, if you are experiencing knee pain for no apparent reason, a misaligned kneecap may be the cause of your symptoms. If you are going to receive a cortisone treatment for plica syndrome, remember that there is a risk of infection any time an injection is made into a joint. Standard sterile technique is used whenever an injection is given. This involves cleansing the skin with an antiseptic such as betadine prior to inserting the needle.

Orthopedic Evaluation [top]

There are usually three parts of an orthopedic evaluation: medical history, physical examination, and tests your physician may order.


Since plica syndrome shares many symptoms with other knee ailments, it is important to be as accurate as possible in describing your symptoms to your doctor. Even then, other possibilities will have to be ruled out before a diagnosis of plica syndrome is made. Your physician also typically will ask about other conditions, such as diabetes and allergies, and medications currently being taken.


Your physician will check for swelling and for the location of pain, and to see if he can feel the plica band. He may ask you to flex and extend your knee while he is performing these tests.

TESTS [top]

Plicae can only be seen through an arthroscope, which will reveal any inflammation that may exist. MRI (magnetic resonance imaging) can detect ligament or cartilage damage, and therefore can rule out those injuries. X-rays can determine other conditions, such as bone injuries. Before arthroscopy is requested, all other possibilities should be considered first.


   Imaging techniques

Rest and Ice
Non-Steroidal Anti-Inflammatory Drugs
Therapeutic Injection
Arthroscopic Excision

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