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Plica Syndrome

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Other Names

  • Synovial Plica Syndrome (SPS)
  • Medial Plica Syndrome




  • Estimated prevalence among European studies is approximately 10%[1]
  • Up to 60% may be bilateral, although often not simultaneously[2]


  • Normal Plicae
    • Inward folds of the synovial lining and are present in most knees
    • Normally, thin and pliable and appear almost transparent
  • Pathologic Plicae
    • Inherent qualities change due to an inflammatory process that alters the pliability of synovial tissue
    • Can become inelastic, tight, thickened, fibrotic, and sometimes hyalinized
  • Can be described by location
    • Suprapatellar
    • Mediopatellar
    • Infrapatellar
    • Lateral (rare, more controversial)


  • General
    • Most important clinically
  • Pathology
    • May bowstring across the femoral trochlea, causing impingement between the patella and femur in knee flexion


  • Majority of cases are idiopathic
  • Other proposed etiologies
    • Trauma (direct, blunt)
    • Twisting injuries
    • Overuse injuries, especially with inadequate healing
    • Repetitive flexion-extension
    • Hematoma
    • Diabetes Mellitus
    • Inflammatory Arthropathy
    • Any cause of synovitis
    • Increased activity levels


  • Plicae
    • Inward folds of synovial lining present in most knees
    • Thin, pliable and almost transparent
    • Embryologically, they form during development and are generally resorbed
  • Mediopatellar Plica[3]
    • Proximally, it attaches to the Articularis Genus Muscle
    • Distally it inserts into the intra-articular synovial lining
    • Blends into the medial patellotibial ligament on the medial aspect of the retropatellar fat pad
  • Suprapatellar
    • From suprapatellar space, extends from the medial wall of the knee toward the lateral wall
  • Ligamentum Mucosum
    • Most common, resides in intercondylar notch

Risk Factors

Differential Diagnosis

Clinical Features

  • History
    • Patients report anterior or anteromedial knee pain
    • Other symptoms include clicking, clunking, buckling, and a popping sensation
    • Often worse with squatting, jumping, stairs, standing, etc
    • In pediatrics, may be associated with period of growth
  • Physical Exam: Physical Exam Knee
    • Mild effusion can be present
    • Can palpate by rolling finger over the plica fold which feels like a ribbonlike fold of tissue
    • Typically found underlying the medial femoral condyle
    • Medial femoral condyle may be tender
  • Special Tests




  • Dynamic Sonography[4]
    • Using arthroscopy to as gold standard
    • Paczesny found Sensitivity 90%, specificity 83%, diagnostic accuracy 88%


  • Findings[5]
    • Hypertrophied plica as a low-intensity signal
    • Often appears normal
    • Better seen if joint is effused


  • Remains gold standard for diagnoses
  • However, not recommended strictly for diagnostic purposes as subsequent scar tissue may worsen symptoms


Ino Classification of Mediopatellar Plica

  • Type A: plicae exist as a thin, cord-like elevation of the synovial wall under the retinaculum.
    • Unlikely to cause symptoms
  • Type B: narrow synovium with a shelf-like appearance, does not cover the anterior surface of the medial femoral condyle
    • Unlikely to cause symptoms
  • Type C: larger, with a shelf-like appearance that partially covers the medial femoral condyle
  • Type D: similar to type C plicae, though this final type is fenestrated, splitting into two portions at its origin

Lyu and Hsu Classification of Mediopatellar Plica

  • Type A plica has no direct contact with the medial femoral condyle
  • Type B plica rides onto, but not beyond half of the condyle
  • Type C plica covers more than half of the medial femoral condyle.
  • Further subclassified into grades I-V based on thickness, degree of fibrosis



  • Younger patients with a shorter course of illness are more likely to respond to conservative measures[6]


  • General
    • First line treatment in vast majority of cases
    • Often directed at underlying etiology (i.e. systemic illness or other structural knee disease)
    • Majority of treatment recommendations based on Patellofemoral Pain Syndrome, not necessarily specific to plica syndrome
  • Activity Modification
    • Modify their activities that are known to exacerbate plica syndrome
    • Examples include high-impact loading such as jumping, squatting, or lunging
  • Physical Therapy
    • Emphasis on Quadriceps strengthening, hamstring stretching
    • Decrease compressive forces in the knee
  • Kinesiology Taping
  • Corticosteroid Injection


  • Indications
    • Failure of conservative management
  • Technique
    • Arthroscopic resection

Rehab and Return to Play


  • Needs to be updated

Return to Play

  • Needs to be updated


See Also


  1. Lee, Paul Yuh Feng, et al. "Synovial plica syndrome of the knee: a commonly overlooked cause of anterior knee pain." The Surgery Journal 3.1 (2017): e9.
  2. Dupont J Y. Synovial plicae of the knee. Controversies and review. Clin Sports Med. 1997;16(01):87–122
  3. Dandy D J. Anatomy of the medial suprapatellar plica and medial synovial shelf. Arthroscopy. 1990;6(02):79–85.
  4. Paczesny L, Kruczynski J. 2009. Medial plica syndrome of the knee: Diagnosis with dynamic sonography. Radiology 251:439–446.
  5. Garcia-Valtuille R, Abascal F, Cerezal I, Garcia-Valtuille A, Pereda T, Canga A, Cruz A. 2002. Anatomy and MR imaging appearances of synovial plicae of the knee. Radiographics 22:775–784.
  6. Sznajderman T, Smorgick Y, Lindner D, Beer Y, Agar G. 2009. Medial plica syndrome. Isr Med Assoc J 11:54–57.
  7. Lyu SR. 2008. Arthroscopic medial release for medial compartment osteoarthritis of the knee: The result of a single surgeon series with minimum follow-up of four years. J Bone Joint Surg Br 90:1186–1192.
Created by:
John Kiel on 7 July 2019 05:31:24
Last edited:
4 October 2022 15:55:01