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
- 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
| Type | Features |
|---|---|
| Suprapatellar | Five types (midline, medial, lateral, incomplete, complete). Complete type seals off pouch completely |
| Medial patellar | Least common. Originates from medial wall of knee joint and runs 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
Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 10 October 2026.