Cyst-like lesions around the knee

There is broad differential for cyst-like lesions around the knee. 

Differential diagnosis

Cysts

• synovial cyst
  • popliteal synovial cyst - Baker cyst
• ganglion cyst
  • intra-articular ganglion cyst
    • ACL ganglion cyst
    • PCL ganglion cyst
    • Hoffa fat pad ganglion cyst
  • extra-articular ganglion cyst
    • periosteal ganglion cyst
    • nerve sheath ganglion cyst 
      • common peroneal nerve sheath ganglion cyst
• meniscal cyst/parameniscal cyst
• intraosseous cyst
  • subchondral cyst (geode)
  • intraosseous ganglion cyst
  • insertional cyst
• infective cyst - abscess

Cyst-like lesions

• distended knee bursae
  • suprapatellar bursa/suprapatellar bursitis
  • prepatellar bursa/prepatellar bursitis
  • superficial infrapatellar bursa/superficial infrapatellar bursitis
  • deep infrapatellar bursa/deep infrapatellar bursitis
  • anserine bursa/pes anserinus bursitis
  • iliotibial bursa/iliotibial bursitis
  • semimembranosus-tibial collateral ligament (SMTCL) bursa/semimembranosus-tibial collateral ligament (SMTCL) bursitis
  • medial collateral ligament bursa/medial collateral ligament bursitis
  • fibular collateral ligament-biceps femoris bursa/fibular collateral ligament)-biceps femoris bursitis
• cystic hematoma/post-traumatic cyst
• normal recesses
  • posterior femoral recess (subgastrocnemius recess) 
  • posterior capsular recess 
  • subpopliteal recess
  • suprahoffatic recess
  • infrahoffatic recess
  • anterior tibial recess
  • central synovial recess
  • parameniscal recess
• popliteal arterial aneurysm - pseudoaneurysm
• popliteal venous varix
• solid lesions with cyst-like components
  • cystic degeneration or myxoid stroma in tumors such as 
    • synovial sarcoma
    • dedifferentiated sarcoma
    • myxoid liposarcoma
    • metastases
    • benign synovial hemangioma