Baker Cyst
Baker Cyst was found in 5-Minute Clinical Consult which helps you diagnose, treat, and follow up on over 900 medical conditions seen in everyday practice.

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Basics

Description

  • A fluid-filled synovial sac arising in the popliteal fossa
  • Distention of the gastrocnemial-semimembranous bursa
  • Can be unilateral or bilateral
  • Most frequent cystic mass around the knee (1)
  • Primary cysts are a distention of the bursa arising independently without an intra-articular disorder.
  • Secondary cysts occur if a communication exists between the bursa and knee joint, allowing articular fluid to fill the cyst. Pathologic joint processes can also be transmitted in this manner.
  • Associated with synovial inflammation
  • Synonym(s): Popliteal cyst

Epidemiology


Incidence
  • Bimodal distribution: Children ages 4–7, and adults increasing with age
  • Primary cysts usually seen in children <15 years of age
  • Secondary cysts seen in the adult population
Prevalence
  • Varies by study
  • Studies report a prevalence of 19–47% in symptomatic knees, 2–5% in asymptomatic knees.
  • In children: 6.3% in symptomatic knees, 2.4% in asymptomatic knees

Risk Factors

  • Osteoarthritis of knee (most common) (2)[B]
  • Rheumatoid arthritis
  • Meniscal degeneration or tear
  • Advancing age
  • Ligamentous insufficiency

Pathophysiology

  • Extension or herniation of synovial membrane of the knee joint capsule or connection of normal bursa with the joint capsule
  • May be the result of increased intra-articular pressure
  • Commonly seen with knee effusions
  • Direct trauma to the bursa is likely the primary cause in children because there is no communication between the bursa and the joint in children.
  • A valvelike mechanism allowing 1-way passage of fluid from the joint to the bursal connection has been described.

Etiology

Associated intra-articular pathological findings include:

  • Meniscal tears, posterior horn
  • Anterior cruciate ligament (ACL) insufficiency
  • Degenerative articular cartilage lesions
  • Rheumatoid arthritis (20%)
  • Osteoarthritis (50%)
  • Osteochondritis
  • Gout (14%)
  • Other potential factors: Infectious arthritis, polyarthritis, villonodular synovitis, lymphoma, sarcoidosis, and connective tissue diseases (3)

Commonly Associated Conditions

Any condition causing knee joint effusion

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