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Plica syndrome

Plica syndrome is the name given to thickened areas of the synovial membrane, which causes pain. We discuss the condition and take a look at the different treatments available, from physiotherapy to surgery.

Many of the body’s joints are held stable by soft tissue known as ligaments and soft tissue capsules that surround them. Lining the inner surface of the joint capsule is another tissue known as the synovial membrane.

The synovial membrane has several roles to play in the function of a joint. These include the production of joint fluid (synovial fluid) to lubricate the joint and reduce joint forces during movement.

Plica, which can be found within the knee, is the name given to thickened areas of the synovial membrane. Researchers have not found an obvious need for common plica in the knee and it is thought they are simply remnants from embryonic development when the knee joint and synovial membrane was split into three compartments.

There are three plica folds of the synovial membrane in the knee. The syndrome can form in any of these three structures, although it is very rare. However, when it does occur, it normally involves a plica fold that runs to the inside of the knee cap.

Thickening of the synovial membrane can form in any aspect of the knee, including in the medial femoral condyle and the intercondylar notch. One of the most common conditions caused by synovial plicae of the knee is called medial patellar plica syndrome. Another is infrapatellar plica.

Some cases of symptomatic plicae begin with a blunt trauma to the area of the knee where a plica runs. Medial plica irritation leads to inflammation, scarring and subsequent thickening of the plica. Sometimes this process occurs with no obvious trauma to the knee.

Once the plica has become inflamed and thickened it is more likely to cause friction between the knee joint and knee cap during certain movements. This can lead to long-term problems of the knee.

Ongoing symptoms of the syndrome include a localised pain over the affected area. The pain is normally on the immediate inside of the knee cap but may be the outside or below the knee cap depending on the exact synovial plica fold affected.

As well as anterior knee pain, there is often a catching sensation or locking feeling to the knee when performing certain movements that cause friction between the plica and against parts of the knee joint.

Sometimes there can be a palpable thickening, which can be felt clunking back and forth. Movements most likely to cause symptoms include deep-squatting actions or rotating movements with the knee flexed.

Plica syndrome will not show up on x-rays and may not show on some forms of imaging such as MRI or ultrasound scans. An initial diagnosis should be made by an experienced orthopaedic knee consultant surgeon.

Depending on the exact history and findings, a consultant may request scans, such as a medial patellar plica MRI scan or ultrasound. Depending on their diagnosis, the consultant may, in some cases, offer an investigative keyhole operation to examine the knee by inserting a camera inside the knee joint.

There is also a provocation test, called a medial plica syndrome test. This can be in the form of a knee extension test or a flexion test. To perform the test, a quick extension of the tibia is performed as though making a kicking movement.

Our hospitals are able to offer short-notice appointments with orthopaedic knee consultants as well as immediate booking for any diagnostic anatomy and MR imaging required.

Individuals who are undergoing initial plica symptoms should rest the knee from aggravating activities and undertake a course or anti-inflammatory medication for six weeks or until the symptoms have resolved. Icing the knee may also help to reduce inflammation.

A gradual return to sports should be attempted after this, being careful not to stress the knee too early in deep-squatting movements.

Physiotherapy plays a limited role in managing the pain caused by plica syndrome. This is because the ailment does not seem to be related to any definite biomedical problem that needs to be fixed. However, a supervised program of strengthening exercises once the condition has calmed down and there is less pain or stiffness following a course of anti-inflammatory drugs may be of benefit.

For cases of plica syndrome that have occurred following a specific trauma or after a specific exercise, it is unlikely that surgery will be offered as the first line of invasive treatment.

Instead, to help settle remaining plica inflammation and pain our consultants may offer you a corticosteroid injection. They will discuss the risks as well as the benefits of this form of treatment during your consultation.

As the syndrome of the knee is a condition that is caused by trauma or through an unidentified mechanism, the symptoms are likely to become more persistent over time. This is due to the scarring and thickening to the synovial folds tissue.

If you are suffering from this condition, then you may be offered a keyhole operation (also called an arthroscopy) to remove the thickened plica.

Prior to medial plica removal, the consultant will determine the exact location of the plica. A small keyhole incision will be made and the source of symptoms will be identified with a camera on the end of a tool known as an arthroscope. The inflamed portion of synovial plica tissue will be removed and the small incision closed.

A course of physical therapy will complete your recovery and get you back on your feet.

Although this form of keyhole surgery is a very safe procedure with very small incisions being needed, there is still a small risk of infection. Any patients undergoing surgical treatment for the syndrome will be closely monitored by their consultant knee surgeon post operatively.

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