Plica syndrome

Definition

• A plica is a band of thick, fibrotic tissue that extends from the synovial capsule of a joint. Plica can be present in multiple joints, but this article will review plica in the knee which is the joint most commonly affected by plica tissue. As a result of overuse or injury, plica can become inflamed or irritated due to friction across the patella or the medial femoral condyle. When the plica becomes inflamed or irritated, it can cause plica syndrome, which is anterior knee pain due to the plica.

Etiology

• Healthcare professionals do not universally agree upon the embryological development of the knee joint. One common theory is the menisci, cruciate ligaments, and a joint cavity all develop when the fetus is 8 weeks old. Over the next 2 weeks, the septa of the Synovium are resorbed, and larger cavitation develops which ultimately becomes the knee joint. If this larger cavitation fails to join together fully, Mesenchymal tissue may develop synovial folds. These synovial folds are plicae.

Epidemiology

• Most report a 10% prevalence of plica syndrome based on arthroscopic studies. It is estimated that plica syndrome is under-diagnosed because the symptoms are similar to other etiologies of knee pain.

Staging

Medial plicae are most commonly symptomatic and can be classified by the Sakakibara arthroscopic classification:

• Type A: Elevation in the synovial wall
• Type B: Appear shelf-like, but not covering the anterior surface of the medial femoral condyle
• Type C: Large, shelf-like appearance and covering the anterior surface of the medial femoral condyle
• Type D: fenestrated plica with a central defect
  

  Plica

Signs and symptoms

• Patients with plica syndrome will experience pain on the anterior aspect of the knee associated with clicking or popping. The anterior knee pain is a hallmark of plica syndrome. Pain can be brought on by rising from a chair, squatting, stairs, or other activities that load the patellofemoral joint.
• The history may include a twisting injury or blunt trauma, or there could be no history of injury or trauma. There are secondary causes of plica that should be considered when obtaining a history. These include Hemarthrosis secondary to hemophilia, intra-articular lesions, loose foreign bodies, and Rheumatoid arthritis.
• On physical exam, a taut band may be palpable under the skin which may be tender to palpation. If this is the case, the Contralateral knee should be examined to see if there is a plica causing tenderness to palpation on that knee as well. Other findings on physical exam may include an effusion, tight hamstrings, and tight quadriceps.
• The Stutter test is performed by having the patient sit upright with the legs dangling off the edge of the exam table at a 90-degree angle. The examiner places his or her index and middle fingers on the center of the patella of the affected leg. The patient then extends the affected leg while the examiner feels for a stutter of the patella. Feeling a stutter is a positive test.
• In the Hughston test, the patient lies supine with the knee extended. The examiner stands on the side of the affected knee with one hand around the plantar aspect of the patient's heel and the other palm covering the patient's patella. The examiner then pushes the patella medially and internally rotates the tibia while taking the patient's knee through flexion and extension. A positive Hughston's test is when the patient experiences pain or the practitioner appreciates popping during the range of motion.

Diagnosis

• Anteroposterior (AP), lateral, and skyline Radiographs should be obtained when plica syndrome is suspected, although they will often be normal even if plica syndrome is the diagnosis.
• MRI (Magnetic resonance imaging) can be useful as part of pre-operative planning and is important in evaluating other potential causes of knee pain.
• The gold standard for diagnosis is Arthroscopy.

Management

• Treatment options for plica syndrome include stretching and strengthening, intraplical Corticosteroid injections, and arthroscopy.
• The Sakakibara classification system is important when considering treatment because type A and B have a low likelihood to cause pain. Type C and D, on the other hand, can impinge on the medial condyle due to their larger size. Type A and B respond much better to conservative therapies than C and D do. As a result, patients with type A and B should be encouraged to attempt conservative therapy first.
• Conservative treatment for plica syndrome can either be performed at home by the patient or via formal physical therapy. Either way, this would involve lower extremity stretching and knee extension exercises with the goal of strengthening the joint capsule musculature, hamstrings, and quadriceps. Nonsteroidal anti-inflammatory drugs (NSAIDS) and ice are reasonable treatments at this stage to calm down inflammation. Conservative management also includes avoiding activities that incite pain. At least 3 months of conservative treatment is recommended before advancing to more aggressive therapies.
• Often the next step if stretching and strengthening do not release symptoms is intraplical corticosteroid injection. This is a reasonable treatment option, especially early in the disease process when conservative management has not provided relief.
• Resection via arthroscopy is a favorable option for medial plicae that do not respond to conservative treatment. Resection is also reasonable when cartilage damage is suspected, such as in type C and D lesions, even if conservative measures have not been completed for 3 months. Another study showed that compared to conservative treatment, arthroscopy yields a greater therapeutic effect for plica syndrome and the effect is longer lasting.

Differential diagnosis

• Osteochondritis dissecans: Differentiated with radiographs and MRI.
• Patellofemoral Subluxation: Patients with patellofemoral subluxation will often provide a history consistent with subluxation and may have apprehension with a displacement of the lateral patella.
• Meniscus pathology: Meniscus pathology will have tenderness at the joint line, whereas plica pain tends to localize above the joint line. Also, physical exam tests such as Apley, Thessaly, bounce home, and/or McMurray can help distinguish the 2 entities.
• Osteoarthritis: Differentiated with radiographs showing decreased joint space, Osteophytes, subchondral sclerosis, subchondral cysts, among others, although this does not rule out also having symptomatic plicae.
• Patellar tendinitis: Differentiated by palpating the patellar tendon on either the proximal or distal attachment.
• Cruciate ligament dysfunction: Differentiated by physical exam techniques suggesting laxity including Lachman, anterior drawer, or posterior drawer that would likely be positive in cruciate ligament injury.
• Pigmented villonodular synovitis (PVNS): Differentiated via MRI.

Prognosis

• Once appropriately treated, there is a favorable prognosis for plica syndrome.

Complications

• One study suggests that the friction between a medial plica and the medial femoral condyle may lead to cartilage damage.
• If left untreated, medial plica syndrome can cause grade IV Outerbridge chondral lesions, which is when the subchondral bonehead is exposed.These are difficult to treat and preventing grade IV Outerbridge lesions from occurring highlights the importance of prompt diagnosis and treatment of plica syndrome.

References

• Kyle Casadei; John Kiel. [Updated April 9,2021]. In StatPearls[Internet]. Available at: https://www.ncbi.nlm.nih.gov/books/NBK535362/
• Gilberto Luís Camanho. Clinics (Sao Paulo). 2010 Mar. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2845763/

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