Medial Synovial Plica Irritation Clinical Presentation

Medial suprapatellar plical irritation is a common finding in patients who present with complaints of anterior knee pain.

Symptoms include complaints of pain and stiffness over the anteromedial aspect of the knee upon arising from a prolonged sitting position, pain going up and/or down stairs, and pain with prolonged activity.

The symptoms often wax and wane over periods of time until the patient presents to a physician's office because of persistent irritation.

Prolonged flexion may increase the pain, and extension might relieve the pain.

Some patients may have had a previous arthroscopy for complaints of medial-sided knee pain without alleviation of their symptoms after the arthroscopy, regardless of whether they had some medial meniscus or medial compartment articular cartilage pathology addressed at the time of their arthroscopy. Such patients usually did not have physical therapy or participate in an exercise program either before or after this surgery.

The examiner can palpate the plica by rolling one's fingers along the tissue between the medial epicondyle and the medial border of the patella. The plica is most commonly palpated about 1-2 fingerbreadths medial to the medial edge of the patella.

Patient pain and irritation upon the examiner rolling the medial suprapatellar plica under his or her fingers is a classic finding on physical examination. The examiner should ascertain whether the elicited pain is due to palpation of this well-innervated area of the synovium or whether the examiner is producing the type of pain that the patient experiences with activities.

Three diagnostic tests have been described for medial plica syndrome. The first is the active extension test during which a patient is asked to make a quick extension movement (eg, kicking). A positive test result occurs when pain (due to tension on the plica from the quadriceps muscles) is elicited with rapid extension. The second test relies on flexion. From full extension, the knee is rapidly flexed to between 30 º and 60 º of knee flexion. As before, the test result is positive when a painful sensation (due to the plica stretching with eccentric contraction of the quadriceps muscle) is elicited. The third test for medial plica syndrome is known as the mediopatellar plica (MPP) test. The patient is placed in a supine position with the affected knee extended. The examiner applies force to the inferomedial portion of the patellofemoral joint whileflexing the knee to 90 º. A positive test result occurs when the patient reports pain relief as the knee goes into flexion.

Irritation (eg, direct trauma, repetitive use) leading to an inflammatory process, which occurs within the joint, can cause the synovial tissue to swell and thicken. Eventually, the normal elastic tissues are replaced with fibrous tissues, leading to a scarred plica. This scarred plica can develop fibrotic bands that extend over the medial trochlea and partially or completely cover the anterior femoral condyle. As the knee flexes, the bands are stretched, causing a painful sensation. Common causes of irritation are listed below:

• 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 Pes Anserine Bursitis (in the Sports Medicine section) and Pes Anserinus Bursitis (in the Physical Medicine and Rehabilitation section).
• Direct trauma to the knee can also result in irritation of the medial plica (eg, dashboard injuries, fall onto a flexed knee), as can twisting injuries and overuse without proper time for healing.
• 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. Anything that causes bleeding in the joint or synovitis can lead to plica irritation. See also Knee, Meniscal Tears (MRI).

Classification

Lino classified medial plicae into 4 types (A, B, C and D) based on their appearance.^[2] Type A plicae appear under the retinaculum as thin, cordlike elevations of the synovial wall. Type B plicae have a shelflike appearance of narrow synovium that does not cover the anterior medial femoral condyle. Type C plicae also have a shelflike appearance, but they are larger and cover part of the anterior medial femoral condyle. Type D medial plicae are fenestrated and have 2 origins within the synovium of the joint. A and B types of medial plicae tend to be smaller and are unlikely to cause symptoms. Types C and D tend to be larger, which increases the chance they can become trapped and be impinged within the patellofemoral joint.

A second classification system based on the work of Lyu and Hsu divides medial plicae into 3 categories (A, B, and C) based on femoral condyle coverage.^[3] Type A plicae have no coverage or contact with the medial femoral condyle. Type B plicae have direct contact with the condyle but do not cover more than half of the anterior surface. Type C plicae obscure greater than half of the medial femoral condyle.