Synovial Plicae of the Knee

Description

Plica of the knee including medial, suprapatellar, infrapatellar and lateral

The four synovial plica of the knee

Location of the synovial plica inside the knee joint.

Name

• Synovial Plicae of the Knee

General

• Plicae are folds of synovium thought to represent embryologic remnants
• Thin, pliable and almost transparent
• Common, seen in ~90% of arthroscopies
• Can be symptomatic depending on the clinical context

Embryology

• Initially separated into three compartments: medial, lateral, suprapatellar
• Between the 9th-12th week they are resorbed, forming a single compartment by week 16
• Plica thought to be remnants of this embryological membrane
• Mesenchymal cells fill the knee at 7 weeks, which coalesce to form a joint cavity at 10 weeks
• Plica may also represent incomplete areas of cavitation, differentiating into synovial folds

Epidemiology

• Four plicae have been described: suprapatellar, infrapatellar, medial patellar, and lateral patellar
• Prevalence varies widely in the literature, ranging from 14% to 100%
• Kim et al: 87% for suprapatellar, 86% for infrapatellar, 72% for medial, and 1.3% for lateral patellar plicae

Major Plicae

• Medial Patellar Plica: most frequent symptomatic knee plica (although not most common)
• Suprapatellar Plica
• Infrapatellar Plica (aka Ligamentum mucosum)
• Lateral Patellar Plica

Minor Plicae

• Lateral
  • Lateral alar fold
  • Superolateral fold
  • Transverse synovial arcuate fold

CT Features

• On arthrography, may appear as a shelf-like band

MRI Features

• Typically seen best on T2 weighted imaging
• Appears as a band-like low signal structure traversing through the joint space (if effusion present)

---

Clinical Significance

• Medial Plica Syndrome

---

See Also

• Knee Anatomy Main
• Physical Exam Knee
• Knee Pain Main

---