Baker’s Cyst / Popliteal Cyst

A Baker’s cyst / a popliteal cyst, is a fluid filled swelling that develops at the back of the knee in midline below the joint line.

It is a pulsion diverticulum of the synovial lining of the knee joint.

Most Baker’s cyst has a communication with the synovial cavity of the knee joint, therefore it is not a true cyst.
 

Causes Of Baker’s Cyst

  1. Chronic diseases involving knee joint 
    • Osteoarthritis
    • Rheumatoid arthritis
  2. Cartilage tear of knee



Management Of Baker’s Cyst

Clinical features

  1. Painless swelling behind the knee 
  2. Knee pain / tightness of the knee when fully flexed or extended
  3. Stiffness of the knee
  4. Symptoms gets worse when the patient is active


Examination 

  1. Lump situated in the midline below the joint line
  2. Oval in shape
  3. Lump disappears when the knee is flexed
  4. Lump reappears when the knee is extended 
  5. Soft in consistency
  6. Brilliantly transillumient
  7. Fluctuation test is positive 
  8. Joint crepitations maybe present 


Investigations

  1. Diagnosed clinically
  2. Ultrasonography can be done, if there is any confusion

 Treatment

  1. Asymptomatic cysts, does not require any treatment 
  2. Treatment of the underlying cause, such as osteoarthritis
  3. Rest and elevation of the affected limb
  4. Analgesics, if pain is present  
  5. Ice pack is also helpful
  6. Aspiration to reduce its size
  7. Corticosteroid injections to reduce inflammation 
  8. Surgical excision is done in symptomatic Baker’s cyst



Surgical Excision Of Baker’s Cyst




Differential Diagnosis Of Baker’s Cyst

  1. Lipoma 



Complications Of Baker’s Cyst

  1. Rupture of the cyst
  2. Sharp pain in the knee
  3. Swelling of the calf muscles  



Ruptured Baker’s Cyst

Presentation

  1. Swelling of the leg below the knee
  2. Pain in the leg
  3. May become red due to inflammation

Treatment

  1. Rest 
  2. Elevation of affected limb
  3. orticosteroid injection 



Surgical Anatomy Of Popliteal Fossa

Boundaries of popliteal fossa

  • Superomedial border
    • Semimembranosus 
  • Superolateral  border
    • Biceps femoris
  • Inferomedial border
    • Medial head of gastrocnemius
  • Inferolateral boarder  
    • Laeral head of gastrocnemius & plantaris

 

Contents of popliteal fossa (From medial to lateral)

  1. Popliteal artery 
  2. Popliteal vein 
  3. Tibial nerve 
  4. Common fibular nerve

 

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