Popliteal Cysts: MRI Finding or Treatable Lesion: Arthroscopic and

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
Better described as “popliteal bursa”
› Located posteromedial between medial
head of gastroc and semimembranosus
tendon
› Coalition of these 2 bursas with flap limiting
communication with joint

Are not
› Posterolateral cysts off popliteus tendon
› Posterior ganglions (Hamstring, other)
› Meniscal cysts (Do not communicate with
meniscus)

Incidence
› 37% knees all knees scoped had opening
into popliteal bursa (Johnson 1997)
› Increasing incidence with increasing age
(Lindgren 1977)
› Often associated with DJD, meniscal tears,
RA, synovitis

Incidence
› 5-58% in patients with knee symptoms
› 30% in cadavers (Guerra 1981)
Posteromedial mass +/- pain usually just
below joint line
 >5 cm likely to be symptomatic
 Pediatric – usually asymptomatic and
resolve

Tibial nerve compression – numbness
 Tibial vein compression – swelling
 Unlikely popliteal artery compression

Rupture – pseudothrombophlebitis
 Chronic dissection or leakage

› Appears similar to DVT
Between Semitendinosus and Medial
Gastrocnemius
 Distal cyst NV “protected” by medial gastroc


In proximal cysts, note proximity to NV
structures
Fibrosarcoma
 Synovial sarcoma
 Malignant fibrous histiocytoma


Non-operative
› NSAI
› Cyst aspiration/injection = intraarticular
aspiration/injection
(DiSante 2010)
› Improvement at 4 months after intraarticular
injection (Acebes 2006)

Operative
› Open
› Arthroscopic

Complications
› Flexion contractures
› Fistulas
› Recurrence
› Nerve injury

Rupp 2002
› Addressed intra-articular pathology only (DID
NOT ADDRESS CYST)
› U/S at 1-3 years
› 11/16 still had cysts – correlated with poor
results
› Correlated with grade III and IV
chondromalacia
Takahashi (Arthroscopy 2005 – technical
note)
 Slit-like structure in posteromedial knee
 Taken down via AL portal or transseptal
approach while visualizing from PM
portal

Sansone – 1999
 Ahn (Arthroscopy 2007, 2010)

› Technical description of flap removal thru
PM portal
› PM “Cystic portal” to excise cyst if fibrous
membrane, nodules, or septa are present

Ahn
› MRI follow up 1-3 years, 31 patients
 All cyst gone or reduced to <1 cm

Routine scope – address all
intraarticular pathology
› Portals hug patellar tendon
Scope to AM portal
 Localize “trifurcation”
 Pass arthroscopic sheath from
AL portal through notch into
PM compartment (direct
visualization)

Place scope in AL portal to visulaize PM
compartment
 May need use AM portal or transpatellar
tendon portal

Needle locate PM portal
 Locate PoTSI

› Posterior
› Transverse
› Synovial
› Infold

Consistently overlying medial head of
gastroc lateral to semimembranosus

Pass working cannula bluntly into PM
portal
› At risk- saphenous nerve!!

Take down PoTSI flap with basket, shavers
Switch scope to PM portal
 Visualize/irrigate cyst
 Loose body removal


To remove cyst if large/loculated
› Locate subcutaneous position of cyst
› Needle loc and use as working portal
› Visualize thru PM portal

4 years- 132 popliteal cyst
decompressions/excisions
› Most decompress only
› 2 patients with recurrent cysts after open
excision
› Multiple loose bodies in cysts

Results
› 2/132 with symptomatic recurrences
› 1 DVT

Decompress popliteal cyst if:
› Symptomatic
› Grade 3 or 4 chondral changes
› Chance of recurrent synovitis (RA, CPPD)
› >5 cm
› Loose bodies seen on mri in cyst
Posterior
 Transverse
 Synovial
 Infold

PoTSI

No PoTSI
Cyst is medial to medial head of gastroc
› Between MHG and semimembranosus
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