Plica

Definition

  • Reduplication of synovial fold
  • Represents normal embryonic synovial septum that persists into adult life

Epidemiology

  • 20% of knees have medial patellar plica at arthroscopy
  • Symptomatic plicae much less common: 1-2%
  • Mean age 14

Pathogenesis

  • knee forms from 3 separate compartments
  • Medial & lateral compartments & suprapatellar pouch separated by membranes in early embryological life
  • Membranes involute & knee becomes single cavity
    • note ACL/PCL/Popliteus are all extrasynovial
  • Persistence of section of membrane occurs leading to plica
  • Therefroe plica in itself is not pathological
  • However if have trauma to knee or other internal derangement
    • synovial inflammation
    • Thickens up
    • Impinges
    • and becomes pathological

Classification

  • Suprapatellar 5 types:
    1. Midline
    2. Medial
    3. Lateral
    4. Incomplete
    5. Complete
    • Complete type seals off pouch completely
  • Medial Patellar
    • least common
    • Originate from medial wall of knee joint
    • Run obliquely down to insert in medial infrapatellar fat pad
    • most likely to be symptomatic
    • gets caught between patella & femur
  • Infrapatellar (Ligamentum Mucosum)
    • From notch to fat pad
    • most common
    • always asymptomatic

Aetiology

  • Becomes pathological when becomes inflamed, stiffened & fibrotic
  • Inflammation can be initiated by:
    • Single blunt trauma
    • Repetitive trauma
    • Internal derangement of knee
  • Causes symptoms when snaps over condyle (especially medially)
  • Leads to:
    • Synovitis
    • Cartilage erosion at condyle
  • Most commonly involves:
    • Superomedial plica
    • Medial patellar plica

Pathology

  • Normal Plica
    • Thin pink & friable
  • Pathological Plica
    • Gross
    • Thickened, white & fibrotic
  • Histology
    • Chronic synovitis & enlargement of villi

Clinical Features

  • History
    • History of trauma or strenuous activity
    • Activity related pain
    • Pain increased with
      • Activity
      • Prolonged sitting
    • Swelling intermittent
    • Painful snapping associated with:
      • Knee flexion
      • Crouching
      • Stairs
    • Instability
    • Locking
  • Signs
    • Quadriceps wasting
    • Effusion
    • Localised tenderness over MFC
    • Palpable band-like structure parallel to medial border of patella
    • Lateral translation of patella causes pain by increasing band tightness

Treatment

  • Nonoperative
    • Restriction of activities
    • ROM & strengthening exercises
  • Operative
    • Arthroscopic resection
    • Divide plica to synovial membrane rather than completely excise
    • 80-90% Good – excellent results