Plica of the Knee

Last updated April 1, 2010, 3:15 PM Sports injury Assessment and Rehabilitation pages 355 - 455 Plica Syndrome

Internet search Medial knee plical syndrome April 1, 2010

These are some selected results with some pertinent highlighted text By Dr. Ouellette.


How does a plica cause problems in the knee?

A plica causes problems when it is irritated. This can occur over a long period of time, such as when the plica is irritated by certain exercises, repetitive motions, or kneeling. Activities that repeatedly bend and straighten the knee, such as running, biking, or use of a stair-climbing 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 even from 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.

X-rays will not show the plica. X-rays are mainly useful to determine if other conditions are present when there is not a clear-cut diagnosis.

How is plica syndrome diagnosed?

Diagnosis 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 may be confused. A MRI may be done, but it is often not terribly helpful in the diagnosis of plica syndrome.

What is the treatment for plica syndrome?

Symptomatic plica syndrome is best treated by resting the knee joint and anti-inflammatory medications. These measures are usually sufficient to allow the inflammation to settle down. Occasionally, an injection of cortisone in to 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 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.

Sport-Specific Biomechanics

The quadriceps muscles and the articularis genu muscle dynamically control the medial suprapatellar plica. Good quadriceps tone seems to result in normal motion of this plica, whereas patients with poor quadriceps tone or tight hamstring muscles (antagonists of the quadriceps) commonly have irritation of their synovial plica.

[NOTE from Dr. Ouellette: Contraction of the quadriceps muscle group when lying on the back with someone pulling on the foot, would cause an acutely inflamed plica to react with pain.]


* Any type of dysfunction of the patellofemoral joint may cause irritation of the medial synovial plica. This dysfunction can be due to overuse, injury, or abnormal mechanics.

* Patients often have concurrent patellar subluxation or apprehension, and this should be assessed as part of the physical examination. In addition, these patients often have a component of tight hamstrings or concurrent irritation of the pes anserine bursa. Measuring the hamstring-popliteal angle allows the examiner to assess the patient's hamstring tightness, whereas direct palpation helps to assess irritation of the pes anserine bursa. (See also the eMedicine article Pes Anserine Bursitis [in the Sports Medicine section] and Pes Anserinus Bursitis [in the Physical Medicine and Rehabilitation section].)

* Direct blows to the knee can also result in irritation of the medial plica (eg, dashboard injuries, fall onto a flexed knee).

* Other pathology in the knee joint, such as a meniscal tear or arthritis, may cause knee effusions or quadriceps atrophy, which could result in plical irritation. (See also the eMedicine article Knee, Meniscal Tears (MRI).)

Case Study

An 18 year old male football player presents with a history suspicious of a medial meniscal tear. This was confirmed by MRI. Surgery was performed to repair the medial meniscal tear. Upon arthroscopic evaluation the plica was found. The MRI did not visualize the plica. This plica was located on the medial synovial lining, running superiorly into the suprapatellar pouch. As can be seen in the picture, the plica is distending the synovial lining into the knee joint. The picture on the left shows the same view of the knee with the plica removed. Notice that the synovial lining is no longer pulled into the joint. The torn meniscus was also addressed.

The athlete was seen in the training room for 5 total visits in a two week span. Treatment emphasized basic quadriceps strength and range of motion. Following his 10 day post-op physician’s visit, the athlete was released to normal strength training (10 day gradual return to previous routine) in the weight room.

[NOTE from Dr. Ouellette: If a plica enters the joint space then weight bearing will be painful. This would explain the need for a cane and the inability to bear weight.]

Conclusion: Dynamic sonography allows detection of abnormalities of medial plicae in the knee, with good sensitivity and specificity.