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Medial Synovial Plica Irritation

Author: Robert F LaPrade, MD, PhD, Professor, Department of Orthopedic Surgery, Divisions of Sports Medicine and Shoulder Services, University of Minnesota Medical School; Director, Orthopedic Biomechanics Lab
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Updated: Feb 28, 2010

Introduction

Background

The medial suprapatellar plica of the knee is an intra-articular synovial fold on the medial aspect of the knee. This plica is one of the most common sources of knee pain in patients; however, a proper rehabilitation program allows most patients to recover from the symptoms associated with irritation of this structure.

Frequency

United States

No exact numbers on the incidence of patients with an irritated synovial plica are available; however, it is estimated that approximately 50% of patients who present with knee pain to a physician's office have some irritation of their patellofemoral joint. In this group of patients, most of them have some amount of suprapatellar plical irritation.

Functional Anatomy

The suprapatellar plica is an intra-articular synovial fold, which has its main component on the medial aspect of the knee. When the knee is in full extension, the suprapatellar plica commonly forms a shelf, which can be palpated by an examiner. Proximally, the plica is attached to the articularis genu muscle. Distally, it is attached to the anterior horn of the medial meniscus and the medial edge of the retropatellar fat pad. In some patients, this plical shelf can become fibrotic and may impinge on the medial edge of the medial femoral condyle.

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.

Clinical

History

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

Physical

• 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.

Causes

• 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).)

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